ASDF M. Koster, Ed.
Internet-Draft KTC Control AB
Intended status: Standards Track C. Bormann, Ed.
Expires: 18 September 2025 Universität Bremen TZI
A. Keränen
Ericsson
17 March 2025
Semantic Definition Format (SDF) for Data and Interactions of Things
draft-ietf-asdf-sdf-23
Abstract
The Semantic Definition Format (SDF) is concerned with Things, namely
physical objects that are available for interaction over a network.
SDF is a format for domain experts to use in the creation and
maintenance of data and interaction models that describe Things. An
SDF specification describes definitions of SDF Objects/SDF Things and
their associated interactions (Events, Actions, Properties), as well
as the Data types for the information exchanged in those
interactions. Tools convert this format to database formats and
other serializations as needed.
About This Document
This note is to be removed before publishing as an RFC.
Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-ietf-asdf-sdf/.
Discussion of this document takes place on the A Semantic Definition
Format for Data and Interactions of Things (ASDF) Working Group
mailing list (mailto:asdf@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/asdf/. Subscribe at
https://www.ietf.org/mailman/listinfo/asdf/.
Source for this draft and an issue tracker can be found at
https://github.com/ietf-wg-asdf/SDF.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 18 September 2025.
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Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Structure of This Document . . . . . . . . . . . . . . . 4
1.2. Terminology and Conventions . . . . . . . . . . . . . . . 5
Programming Platform Terms . . . . . . . . . . . . . . . . . 5
Conceptual Terms . . . . . . . . . . . . . . . . . . . . . . 6
Specification Language Terms . . . . . . . . . . . . . . . . 6
Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 8
2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1. Example Definition . . . . . . . . . . . . . . . . . . . 9
2.2. Elements of an SDF model . . . . . . . . . . . . . . . . 11
2.2.1. sdfObject . . . . . . . . . . . . . . . . . . . . . . 12
2.2.2. sdfProperty . . . . . . . . . . . . . . . . . . . . . 13
2.2.3. sdfAction . . . . . . . . . . . . . . . . . . . . . . 14
2.2.4. sdfEvent . . . . . . . . . . . . . . . . . . . . . . 15
2.2.5. sdfData . . . . . . . . . . . . . . . . . . . . . . . 15
2.2.6. sdfThing . . . . . . . . . . . . . . . . . . . . . . 16
2.3. Member names: Given Names and Quality Names . . . . . . . 16
2.3.1. Given Names and Quality Names . . . . . . . . . . . . 16
2.3.2. Hierarchical Names . . . . . . . . . . . . . . . . . 17
2.3.3. Extensibility of Given Names and Quality Names . . . 18
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3. SDF structure . . . . . . . . . . . . . . . . . . . . . . . . 19
3.1. Information block . . . . . . . . . . . . . . . . . . . . 19
3.2. Namespaces block . . . . . . . . . . . . . . . . . . . . 21
3.3. Definitions block . . . . . . . . . . . . . . . . . . . . 22
3.4. Top-level Affordances and sdfData . . . . . . . . . . . . 23
4. Names and namespaces . . . . . . . . . . . . . . . . . . . . 23
4.1. Structure . . . . . . . . . . . . . . . . . . . . . . . . 23
4.2. Contributing global names . . . . . . . . . . . . . . . . 24
4.3. Referencing global names . . . . . . . . . . . . . . . . 25
4.4. sdfRef . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.4.1. Resolved models . . . . . . . . . . . . . . . . . . . 28
4.5. sdfRequired . . . . . . . . . . . . . . . . . . . . . . . 29
4.6. Common Qualities . . . . . . . . . . . . . . . . . . . . 32
4.7. Data Qualities . . . . . . . . . . . . . . . . . . . . . 32
4.7.1. sdfType . . . . . . . . . . . . . . . . . . . . . . . 34
4.7.2. sdfChoice . . . . . . . . . . . . . . . . . . . . . . 35
5. Keywords for definition groups . . . . . . . . . . . . . . . 37
5.1. sdfObject . . . . . . . . . . . . . . . . . . . . . . . . 37
5.2. sdfProperty . . . . . . . . . . . . . . . . . . . . . . . 38
5.3. sdfAction . . . . . . . . . . . . . . . . . . . . . . . . 39
5.4. sdfEvent . . . . . . . . . . . . . . . . . . . . . . . . 39
5.5. sdfData . . . . . . . . . . . . . . . . . . . . . . . . . 40
6. High Level Composition . . . . . . . . . . . . . . . . . . . 40
6.1. Paths in the model namespaces . . . . . . . . . . . . . . 41
6.2. Modular Composition . . . . . . . . . . . . . . . . . . . 41
6.2.1. Use of the "sdfRef" keyword to re-use a definition . 41
6.3. sdfThing . . . . . . . . . . . . . . . . . . . . . . . . 42
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 43
7.1. Media Type . . . . . . . . . . . . . . . . . . . . . . . 43
7.2. Content-Format . . . . . . . . . . . . . . . . . . . . . 44
7.3. IETF URN Sub-namespace for Unit Names
(urn:ietf:params:unit) . . . . . . . . . . . . . . . . . 45
7.4. SenML registry group . . . . . . . . . . . . . . . . . . 45
7.5. Registries . . . . . . . . . . . . . . . . . . . . . . . 46
7.5.1. Quality Names . . . . . . . . . . . . . . . . . . . . 46
7.5.2. Quality Name Prefixes . . . . . . . . . . . . . . . . 48
7.5.3. sdfType Values . . . . . . . . . . . . . . . . . . . 49
7.5.4. Feature Names . . . . . . . . . . . . . . . . . . . . 49
8. Security Considerations . . . . . . . . . . . . . . . . . . . 50
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 51
9.1. Normative References . . . . . . . . . . . . . . . . . . 51
9.2. Informative References . . . . . . . . . . . . . . . . . 54
Appendix A. Formal Syntax of SDF . . . . . . . . . . . . . . . . 57
Appendix B. json-schema.org Rendition of SDF Syntax . . . . . . 62
Appendix C. Data Qualities inspired by json-schema.org . . . . . 104
C.1. type "number", type "integer" . . . . . . . . . . . . . . 104
C.2. type "string" . . . . . . . . . . . . . . . . . . . . . . 105
C.3. type "boolean" . . . . . . . . . . . . . . . . . . . . . 106
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C.4. type "array" . . . . . . . . . . . . . . . . . . . . . . 106
C.5. type "object" . . . . . . . . . . . . . . . . . . . . . . 106
C.6. Implementation notes . . . . . . . . . . . . . . . . . . 107
Appendix D. Composition Examples . . . . . . . . . . . . . . . . 107
D.1. Outlet Strip Example . . . . . . . . . . . . . . . . . . 107
D.2. Refrigerator-Freezer Example . . . . . . . . . . . . . . 108
Appendix E. Some Changes From Earlier Drafts . . . . . . . . . . 109
List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . 110
List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . 110
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 111
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 111
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 111
1. Introduction
The Semantic Definition Format (SDF) is concerned with Things, namely
physical objects that are available for interaction over a network.
SDF is a format for domain experts to use in the creation and
maintenance of data and interaction models that describe Things. An
SDF specification describes definitions of SDF Objects/SDF Things and
their associated interactions (Events, Actions, Properties), as well
as the Data types for the information exchanged in those
interactions. Tools convert this format to database formats and
other serializations as needed.
SDF is designed to be an extensible format. The present document
constitutes the base specification for SDF: "base SDF" for short. In
addition, SDF extensions can be defined, some of which may make use
of extension points specifically defined for this in base SDF. One
area for such extensions would be refinements of SDF's abstract
interaction models into protocol bindings for specific ecosystems
(e.g., [I-D.bormann-asdf-sdf-mapping]). For the use of certain other
extensions, it may be necessary to indicate in the SDF document using
them that a specific extension is in effect; see Section 3.1 for
details of the features quality that can be used for such
indications. With extension points and feature indications
available, base SDF does not define a "version" concept for the SDF
format itself (as opposed to version indications within SDF documents
indicating their own evolution, see Section 3.1).
1.1. Structure of This Document
After introductory material and an overview (Section 2) over the
elements of the model and over the different kinds of names used,
Section 3 introduces the main components of an SDF model. Section 4
revisits names and structures them into namespaces. Section 5
discusses the inner structure of the Objects defined by SDF, the
sdfObjects, in further detail. Section 6 discusses how SDF supports
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composition. Conventional Sections (IANA Considerations, Security
Considerations, Normative References, and Informative References)
follow. The normative Appendix A defines the syntax of SDF in terms
of its JSON structures, employing the Concise Data Definition
Language (CDDL) [RFC8610]. This is followed by the informative
Appendix B, a rendition of the SDF syntax in a "JSON Schema" format
as they are defined by json-schema.org (collectively called JSO).
The normative Appendix C defines certain terms ("data qualities")
used at the SDF data model level that were inspired by JSO. The
informative Appendix D provides a few examples for the use of
composition in SDF. Finally, Appendix E provides some historical
information that can be useful in upgrading earlier, pre-standard SDF
models and implementations to SDF base.
1.2. Terminology and Conventions
Terms introduced in this section are capitalized when used in this
section; to maintain readability, capitalization is only done when
needed where they are used in the body of this document.
Programming Platform Terms
The following definitions mention terms that are used with specific
meanings in various programming platforms, but often have an
independent definition for this document, which can be found further
below in this section.
Element: A generic term used here in its English sense.
Exceptionally, in Appendix C, used explicitly in accordance with
its meaning in the JSON ecosystem, i.e., the elements of JSON
arrays.
Entry: A key-value pair in a map. (In JSON maps, sometimes also
called "member".)
Map: A collection of entries (key-value pairs), where there are no
two entries with equivalent keys. (Also known as associative
array, dictionary, or symbol table.)
Object: An otherwise very generic term that JavaScript (and thus
JSON) uses for the kind of maps that were part of the original
languages from the outset. In this document, Object is used
exclusively in its general English meaning or as the colloquial
shorthand for sdfObject, even if the type name "object" is
imported with JSON-related semantics from a data definition
language.
Property: Certain environments use the term "property" for a JSON
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concept that JSON calls "member" and is called "entry" here, or
sometimes just for the map key of these. In this document, the
term Property is specifically reserved for a certain kind of
Affordance, even if the map key "properties" is imported with
JSON-related semantics from a data definition language.
Byte: This document uses the term "byte" in its now-customary sense
as a synonym for "octet".
Conceptual Terms
Thing: A physical item that is also available for interaction over a
network.
Element: A part or an aspect of something abstract; i.e., the term
is used here in its usual English definition.
Affordance: An element of an interface offered for interaction.
Such an element becomes an Affordance when information is
available (directly or indirectly) that indicates how it can or
should be used. In the present document, the term is used for the
digital (network-directed) interfaces of a Thing only; as it is a
physical object as well, the Thing might also have physical
affordances such as buttons, dials, and displays. The
specification language offers certain ways to create sets of
related Affordances and combine them into "Groupings" (see below).
Property: An Affordance that can potentially be used to read, write,
and/or observe state (current/stored information) on a Grouping.
Action: An Affordance that can potentially be used to perform a
named operation on a Grouping.
Event: An Affordance that can potentially be used to obtain
information about what happened to a Grouping.
Specification Language Terms
SDF Document: Container for SDF Definitions, together with data
about the SDF Document itself (information block). Represented as
a JSON text representing a single JSON map, which is built from
nested maps.
SDF Model: Definitions and declarations that model the digital
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interaction opportunities offered by one or more kinds of Things,
represented by Groupings (sdfObjects and sdfThings). An SDF Model
can be fully contained in a single SDF Document, or it can be
built from an SDF Document that references definitions and
declarations from additional SDF documents.
Block: One or more entries in a JSON map that is part of an SDF
specification; these entries can be described as a Block to
emphasize that they together serve a specific function.
Group: An entry in the main JSON map that represents the SDF
document, and in certain nested definitions. A group has a Class
Name Keyword as its key and a map of named definition entries
(Definition Group) as a value.
Class Name Keyword: One of sdfThing, sdfObject, sdfProperty,
sdfAction, sdfEvent, or sdfData; the Classes for these type
keywords are capitalized and prefixed with sdf.
Class: Abstract term for the information that is contained in groups
identified by a Class Name Keyword.
Quality: A metadata item in a definition or declaration which says
something about that definition or declaration. A quality is
represented in SDF as an entry in a JSON map (JSON object) that
serves as a definition or declaration. (The term "Quality" is
used because another popular term, "Property", already has a
different meaning.)
Definition: An entry in a Definition Group. The entry creates a new
semantic term for use in SDF models and associates it with a set
of qualities. Unless the Class Name Keyword of the Group also
makes it a Declaration (see Section 3.3), a definition just
defines a term, it does not create a component item within the
enclosing definition.
Declaration: A definition within an enclosing definition that is
intended to create a component item within that enclosing
definition. Every declaration can also be used as a definition
for reference elsewhere.
Grouping: An sdfThing or sdfObject, i.e., (directly or indirectly) a
description for a combination of Affordances.
Object, sdfObject: A Grouping that contains Affordance declarations
(Property, Action, and Event declarations) only. It serves as the
main "atom" of reusable semantics for model construction,
representing the interaction model for a Thing that is simple
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enough to not require nested structure. sdfObjects are therefore
similar to sdfThings but do not allow nesting, i.e., they cannot
contain other Groupings (sdfObjects or sdfThings).
sdfThing: A Grouping that can contain nested Groupings (sdfThings
and sdfObjects). Like sdfObject, it can also contain Affordance
declarations (Property, Action, and Event declarations). (Note
that "Thing" has a different meaning from sdfThing and therefore
is not available as a colloquial shorthand of sdfThing.)
Augmentation Mechanism: A companion document to a base SDF Model
that provides additional information ("augments" the base
specification). The information may be for use in a specific
ecosystem or with a specific protocol ("Protocol Binding"). No
specific Augmentation Mechanisms are defined in base SDF. A
simple mechanism for such augmentations has been discussed as a
"mapping file" [I-D.bormann-asdf-sdf-mapping].
Protocol Binding: A companion document to an SDF Model that defines
how to map the abstract concepts in the model into the protocols
in use in a specific ecosystem. The Protocol Binding might supply
URL components, numeric IDs, and similar details. Protocol
Bindings are one case of an Augmentation Mechanism.
Conventions
Regular expressions that are used in the text as a "pattern" for some
string are interpreted as per [RFC9485]. (Note that a form of
regular expressions is also used as values of the quality pattern;
see Appendix C.2.)
The term "URI" in this document always refers to "full" URIs ("URI"
in Section 3 of RFC 3986 [STD66]), never to relative URI references
("relative-ref" in Section 4.1 of RFC 3986 [STD66]), so the term
"URI" does _NOT_ serve as the colloquial abbreviation of "URI-
Reference" it is often used for. Therefore, the "reference
resolution" process defined in Section 5 of RFC 3986 [STD66] is _NOT_
used in this specification. Where necessary, full URIs are assembled
out of substrings by simple concatenation, e.g. when CURIEs are
expanded (Section 4.3), or when a global name is formed out of a
namespace absolute-URI (Section 5 of RFC 3986 [STD66]) and a fragment
identifier part (Section 4.1). Note also that URIs are not only used
to construct the SDF models, they are also the _subject_ of SDF
models where they are used as data in actual interactions (and could
even be represented as relative references there); these two usages
are entirely separate.
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The singular form is chosen as the preferred one for the keywords
defined in this specification.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[BCP14] (RFC2119) (RFC8174) when, and only when, they appear in all
capitals, as shown here.
2. Overview
2.1. Example Definition
The overview starts with an example for the SDF definition of a
simple sdfObject called "Switch" (Figure 1).
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{
"info": {
"title": "Example document for SDF (Semantic Definition Format)",
"version": "2019-04-24",
"copyright": "Copyright 2019 Example Corp. All rights reserved.",
"license": "https://example.com/license"
},
"namespace": {
"cap": "https://example.com/capability/cap"
},
"defaultNamespace": "cap",
"sdfObject": {
"Switch": {
"sdfProperty": {
"value": {
"description":
"The state of the switch; false for off and true for on.",
"type": "boolean"
}
},
"sdfAction": {
"on": {
"description":
"Turn the switch on; equivalent to setting value to true."
},
"off": {
"description":
"Turn the switch off; equivalent to setting value to false."
},
"toggle": {
"description":
"Toggle the switch; equivalent to setting value to its complement."
}
}
}
}
}
Figure 1: A simple example of an SDF document
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This is a model of a switch. The state value declared in the
sdfProperty group, represented by a Boolean, will be true for "on"
and will be false for "off". The actions on or off declared in the
sdfAction group are redundant with setting the value and are in the
example to illustrate that there are often different ways of
achieving the same effect. The action toggle will invert the value
of the sdfProperty value, so that 2-way switches can be created;
having such action will avoid the need for first retrieving the
current value and then applying/setting the inverted value.
The sdfObject group lists the affordances of Things modeled by this
sdfObject. The sdfProperty group lists the property affordances
described by the model; these represent various perspectives on the
state of the sdfObject. Properties can have additional qualities to
describe the state more precisely. Properties can be annotated to be
read, write or read/write; how this is actually done by the
underlying transfer protocols is not described in the SDF model but
left to companion protocol bindings. Properties are often used with
RESTful paradigms [I-D.irtf-t2trg-rest-iot], describing state. The
sdfAction group is the mechanism to describe other interactions in
terms of their names, input, and output data (no data are used in the
example), as in a POST method in REST or in a remote procedure call.
The example toggle is an Action that changes the state based on the
current state of the Property named value. (The third type of
affordance is Events, which are not described in this example.)
In the JSON representation, the info group is an exception in that
this group's map has keys taken from the SDF vocabulary. All other
groups (such as namespace, sdfObject) have maps with keys that are
freely defined by the model writer (Switch, value, on, etc.); these
map keys are therefore called _given names_. The groups made up of
entries with given names as keys usually use the named<> production
in the formal syntax of SDF (Appendix A). Where the values of these
entries are maps, these again use SDF vocabulary keys, and so on,
generally alternating in further nesting. The SDF-defined vocabulary
items used in the hierarchy of such groups are often, but not always,
called _quality names_ or _qualities_. See Section 2.3 for more
information about naming in SDF.
2.2. Elements of an SDF model
The SDF language uses six predefined Class Name Keywords for modeling
connected Things which are illustrated in Figure 2 (limited rendition
in the plaintext form of this document, please use typographic forms
for full information).
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,--------.
|sdfThing|------.
,--------------|--------| | hasThing
| |--------|<-----'
| `--------'
| | | |
| hasObject | | \
| v | \
| ,---------. | \
| |sdfObject| | \
| |---------| | \
,--------|---------|---------.
| `---------' | |
has|Property | hasAction | hasEvent
v v v v
,-----------. ,---------. ,--------.
|sdfProperty| |sdfAction| |sdfEvent|
|-----------| |---------| |--------|
|-----------| |---------| |--------|
`-----------' `---------' `--------'
| hasInput| |hasOutput |
| Data| |Data |
| v v |
| ,-------. |
| isInst |sdfData| hasOutp |
`----------->|-------|<----------'
anceOf |-------| utData
`-------'
Figure 2: Main classes used in SDF models
The six main Class Name Keywords are discussed below.
2.2.1. sdfObject
sdfObjects, the items listed in an sdfObject definition group, are
the main "atom" of reusable semantics for model construction. The
concept aligns in scope with common definition items from many IoT
modeling systems, for example ZigBee Clusters [ZCL], OMA SpecWorks
LwM2M Objects [OMA], OCF Resource Types [OCF], and W3C Web of Things
[WoT].
An sdfObject definition contains a set of sdfProperty, sdfAction, and
sdfEvent definitions that describe the interaction affordances
associated with some scope of functionality.
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For the granularity of definition, sdfObject definitions are meant to
be kept narrow enough in scope to enable broad reuse and
interoperability. For example, defining a light bulb using separate
sdfObject definitions for on/off control, dimming, and color control
affordances will enable interoperable functionality to be configured
for diverse product types. An sdfObject definition for a common on/
off control may be used to control many different kinds of Things
that require on/off control.
The presence of one or both of the optional qualities "minItems" and
"maxItems" defines the sdfObject as an array, i.e., all the
affordances defined for the sdfObject exist a number of times,
indexed by a number constrained to be between minItems and maxItems,
inclusive, if given. (Note: Setting "minItems" to zero and leaving
out "maxItems" puts the minimum constraints on that array.)
2.2.2. sdfProperty
sdfProperty is used to model elements of state within Things modeled
by the enclosing grouping.
A named definition entry in an sdfProperty may be associated with
some protocol affordance to enable the application to obtain the
state variable and, optionally, modify the state variable.
Additionally, some protocols provide for in-time reporting of state
changes. (These three aspects are described by the qualities
readable, writable, and observable defined for an sdfProperty.)
Definitions in sdfProperty groups look like the definitions in
sdfData groups. However, they actually also declare that a Property
with the given qualities potentially is present in the containing
sdfObject.
For definitions in sdfProperty and sdfData, SDF provides qualities
that can constrain the structure and values of data allowed in the
interactions modeled by them. It also provides qualities that
associate semantics to these data, such as engineering units and unit
scaling information.
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For the data definition within sdfProperty or sdfData, SDF borrows
some vocabulary proposed for the drafts 4 [JSO4] [JSO4V] and 7 [JSO7]
[JSO7V] of the json-schema.org "JSON Schema" format (collectively
called JSO here), enhanced by qualities that are specific to SDF.
Details about the JSO-inspired vocabulary are in Appendix C. For
base SDF, data are constrained to be of simple types (number, string,
Boolean), JSON maps composed of named data, and arrays of these
types. Syntax extension points are provided that can be used to
provide richer types in a future extension of this specification
(possibly more of which can be borrowed from json-schema.org).
Note that sdfProperty definitions (and sdfData definitions in
general) are not intended to constrain the formats of data used for
communication over network interfaces. Where needed, data
definitions for payloads of protocol messages are expected to be part
of the protocol binding.
2.2.3. sdfAction
The sdfAction group contains declarations of Actions, which model
affordances that, when triggered, have an effect that can go beyond
just reading, updating, or observing Thing state. Actions often
result in some outward physical effect (which, itself, cannot be
modeled in SDF). From a programmer's perspective, they might be
considered to be roughly analogous to method calls.
Actions may have data parameters: these are modeled as a single item
of input data and output data, each. Where multiple parameters need
to be modeled, an "object" type can be used to combine these
parameters into one; for an example see Figure 6 in Appendix C.5.
Actions may be long-running, that is to say that the effects may not
take place immediately as would be expected for an update to an
sdfProperty; the effects may play out over time and emit action
results. Actions may also not always complete and may result in
application errors, such as an item blocking the closing of an
automatic door.
One idiom for giving an action initiator status and control about the
ongoing action is to provide a URI for an ephemeral "action resource"
in the sdfAction output data, allowing the action to deliver
immediate feedback (including errors that prevent the action from
starting) and the action initiator to use the action resource for
further observation or modification of the ongoing action (including
canceling it). Base SDF does not provide any tailored support for
describing such action resources; an extension for modeling links in
more detail (for instance, [I-D.bormann-asdf-sdftype-link]) may be
all that is needed to fully enable modeling them.
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Actions may have (or lack) the characteristics of idempotence and
side-effect safety (see Section 9.2 of RFC 9110 [STD97] for more on
these terms).
Base SDF only provides data constraint modeling and semantics for the
input and output data of definitions in sdfAction groups. Again,
data definitions for payloads of protocol messages, and detailed
protocol settings for invoking the action, are expected to be part of
the protocol binding.
2.2.4. sdfEvent
The sdfEvent group contains declarations of Events, which model
affordances that inform about "happenings" associated with a Thing
modeled by the enclosing sdfObject; these may result in a signal
being stored or emitted as a result.
Note that there is a trivial overlap with sdfProperty state changes,
which may also be defined as events but are not generally required to
be defined as such. However, Events may exhibit certain ordering,
consistency, and reliability requirements that are expected to be
supported in various implementations of sdfEvent that do distinguish
sdfEvent from sdfProperty. For instance, while a state change may
simply be superseded by another state change, some events are
"precious" and need to be preserved even if further events follow.
Base SDF only provides data constraint modeling and semantics for the
output data of Event affordances. Again, data definitions for
payloads of protocol messages, and detailed protocol settings for
soliciting the event, are expected to be part of the protocol
binding.
2.2.5. sdfData
Definitions in sdfData groups do not themselves specify affordances.
These definitions are provided separately from those in sdfProperty
groups to enable common modeling patterns, data constraints, and
semantic anchor concepts to be factored out for data items that make
up sdfProperty items and serve as input and output data for sdfAction
and sdfEvent items. The data types defined in sdfData definitions
only spring to life by being referenced in one of these contexts
(directly or indirectly via some other sdfData definitions).
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It is a common use case for such a data definition to be shared
between an sdfProperty item and input or output parameters of an
sdfAction or output data provided by an sdfEvent. sdfData definitions
also enable factoring out extended application data types such as
mode and machine state enumerations to be reused across multiple
definitions that have similar basic characteristics and requirements.
2.2.6. sdfThing
Back at the top level, the sdfThing group enables definition of
models for complex devices that will use one or more sdfObject
definitions. Like sdfObject, sdfThing groups allow for the inclusion
of interaction affordances, sdfData, as well as "minItems" and
"maxItems" qualities. Therefore, they can be seen as a superset of
sdfObject groups, additionally allowing for composition.
As a result, an sdfThing directly or indirectly contains a set of
sdfProperty, sdfAction, and sdfEvent definitions that describe the
interaction affordances associated with some scope of functionality.
A definition in an sdfThing group can refine the metadata of the
definitions it is composed of: other definitions in sdfThing groups
or definitions in sdfObject groups.
2.3. Member names: Given Names and Quality Names
SDF documents are JSON maps that mostly employ JSON maps as member
values, which in turn mostly employ JSON maps as their member values,
and so on. This nested structure of JSON maps creates a tree, where
the edges are the member names (map keys) used in these JSON maps.
(In certain cases, where member names are not needed, JSON arrays may
be interspersed in this tree.)
2.3.1. Given Names and Quality Names
For any particular JSON map in an SDF document, the set of member
names that are used is either of:
* A set of "_Quality Names_", where the entries in the map are
Qualities. Quality Names are defined by the present specification
and its extensions, together with specific semantics to be
associated with the member value given with a certain Quality
Name.
* A set of "_Given Names_", where the entries in the map are
separate entities (definitions, declarations, etc.) that each have
names that are chosen by the SDF document author in order that
these names can be employed by a user of that model.
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In a path from the root of the tree to any leaf, Quality Names and
Given Names roughly alternate (with the information block,
Section 3.1, as a prominent exception).
The meaning of the JSON map that is the member value associated with
a Given Name is derived from the Quality Name that was used as the
member name associated to the parent. In the CDDL grammar given in
Appendix A, JSON maps with member names that are Given Names are
defined using the CDDL generic rule reference named<membervalues>,
where membervalues is in turn the structure of the member values of
the JSON map, i.e., the value of the member named by the Given Name.
As quality-named maps and given-named maps roughly alternate in a
path down the tree, membervalues is usually a map built from Quality
Names as keys.
2.3.2. Hierarchical Names
From the outside of a specification, Given Names are usually used as
part of a hierarchical name that looks like a JSON pointer [RFC6901],
itself generally rooted in (used as the fragment identifier in) an
outer namespace that looks like an https:// URL (see Section 4).
As Quality Names and Given Names roughly alternate in a path into the
model, the JSON pointer part of the hierarchical name also alternates
between Quality Names and Given Names.
Note that the actual Given Names may need to be encoded when
specified via the JSON pointer fragment identifier syntax, and that
there are two layers of such encoding: tilde encoding of ~ and / as
per Section 3 of [RFC6901], and then percent encoding of the tilde-
encoded name into a valid URI fragment as per Section 6 of [RFC6901].
For example, when a model is using the Given Name
warning/danger alarm
(with an embedded slash and a space) for an sdfObject, that sdfObject
may need to be referenced as
#/sdfObject/warning~1danger%20alarm
To sidestep potential interoperability problems, it is probably wise
to avoid characters in Given Names that need such encoding (Quality
Names are already defined in such a way that they never do).
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2.3.3. Extensibility of Given Names and Quality Names
In SDF, both Quality Names and Given Names are _extension points_.
This is more obvious for Quality Names: Extending SDF is mostly done
by defining additional qualities. To enable non-conflicting third
party extensions to SDF, qualified names (names with an embedded
colon) can be used as Quality Names.
A nonqualified Quality Name is composed of ASCII letters, digits, and
$ signs, starting with a lower case letter or a $ sign (i.e., using a
pattern of "[a-z$][A-Za-z$0-9]*"). Names with $ signs are intended
to be used for functions separate from most other names; for
instance, in this specification $comment is used for the comment
quality (the presence or absence of a $comment quality does not
change the meaning of the SDF model). Names that are composed of
multiple English words can use the "lowerCamelCase" convention
[CamelCase] for indicating the word boundaries; no other use is
intended for upper case letters in quality names.
A qualified Quality Name is composed of a Quality Name Prefix, a :
(colon) character, and a nonqualified Quality Name. Quality Name
Prefixes are registered in the "Quality Name Prefixes" registry in
the "Semantic Definition Format (SDF)" registry group
(Section 7.5.2). They are composed of lower case ASCII letters and
digits, starting with a lower case ASCII letter (i.e., using a
pattern of "[a-z][a-z0-9]*").
Given Names are not restricted by the formal SDF syntax. To enable
non-surprising name translations in tools, combinations of ASCII
alphanumeric characters and - (ASCII hyphen/minus) are preferred,
typically employing kebab-case for names constructed out of multiple
words [KebabCase]. ASCII hyphen/minus can then unambiguously be
translated to an ASCII _ underscore character and back depending on
the programming environment. Some styles also allow a dot (".") in
given names. Given Names are often sufficiently self-explanatory
that they can be used in place of the label quality if that is not
given. In turn, if a given name turns out too complicated, a more
elaborate label can be given and the given name kept simple. As
given names are "programmers' names", base SDF does not address
internationalization of given names. (More likely qualities to
receive localizable equivalents by exercising the quality name
extension point are label and description).
Further, to enable Given Names to have a more powerful role in
building global hierarchical names, an extension is planned that
makes use of qualified names for Given Names. So, until that
extension is defined, Given Names with one or more embedded colons
are reserved and MUST NOT be used in an SDF document.
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All names in SDF are case-sensitive.
3. SDF structure
SDF definitions are contained in SDF documents, together with data
about the SDF document itself (information block). Definitions and
declarations from additional SDF documents can be referenced;
together with the definitions and declarations in the referencing SDF
document they build the SDF model expressed by that SDF document.
Each SDF document is represented as a single JSON map. This map can
be thought of as having three blocks: the information block, the
namespaces block, and the definitions block. These blocks contain
zero or more JSON name/value pairs, the names of which are quality
names and the values of which mostly are (nested) maps (the exception
defined in SDF base is the defaultNamespace quality, the value of
which is a text string). An empty nested map of this kind is
equivalent to not having the quality included at all.
3.1. Information block
The information block contains generic metadata for the SDF document
itself and all included definitions. To enable tool integration, the
information block is optional in the grammar of SDF; most processes
for working with SDF documents will have policies that only SDF
documents with an info block can be processed. It is therefore
RECOMMENDED that SDF validator tools emit a warning when no
information block is found.
The keyword (map key) that defines an information block is "info".
Its value is a JSON map in turn, with a set of entries that represent
qualities that apply to the included definition.
Qualities of this map are shown in Table 1. None of these qualities
are required or have default values that are assumed if the quality
is absent.
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+-------------+----------+---------------------------------+
| Quality | Type | Description |
+-------------+----------+---------------------------------+
| title | string | A short summary to be displayed |
| | | in search results, etc. |
| description | string | Long-form text description (no |
| | | constraints) |
| version | string | The incremental version of the |
| | | definition |
| modified | string | Time of the latest modification |
| copyright | string | Link to text or embedded text |
| | | containing a copyright notice |
| license | string | Link to text or embedded text |
| | | containing license terms |
| features | array of | List of extension features used |
| | strings | |
| $comment | string | Source code comments only, no |
| | | semantics |
+-------------+----------+---------------------------------+
Table 1: Qualities of the Information Block
The version quality is used to indicate version information about the
set of definitions in the SDF document. The version is RECOMMENDED
to be lexicographically increasing over the life of a model: a newer
model always has a version string that string-compares higher than
all previous versions. This is easily achieved by following the
convention to start the version with an [RFC3339] date-time or, if
new versions are generated less frequently than once a day, just the
full-date (i.e., YYYY-MM-DD); in many cases, that will be all that is
needed (see Figure 1 for an example). This specification does not
give a strict definition for the format of the version string but
each using system or organization should define internal structure
and semantics to the level needed for their use. If no further
details are provided, a date-time or full-date in this field can be
assumed to indicate the latest update time of the definitions in the
SDF document.
The modified quality can be used with a value using [RFC3339] date-
time (with Z for time-zone) or full-date format to express time of
the latest revision of the definitions.
The license string is preferably either a URI that points to a web
page with an unambiguous definition of the license, or an [SPDX]
license identifier. (As an example, for models to be handled by the
One Data Model liaison group, this license identifier will typically
be "BSD-3-Clause".)
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The features quality can be used to list names of critical (i.e.,
cannot be safely ignored) SDF extension features that need to be
understood for the definitions to be properly processed. Extension
feature names will be specified in extension documents. They can
either be registered (see Section 7.5.4 for specifics, which make
sure that a registered feature name does not contain a colon) or be a
URI (which always contain a colon). Note that SDF processors are not
expected to, and normally SHOULD NOT, dereference URIs used as
feature names; any representation retrievable under such a URI could
be useful to humans, though. (See [I-D.bormann-t2trg-deref-id] for a
more extensive discussion of dereferenceable identifiers).
3.2. Namespaces block
The namespaces block contains the namespace map and the
defaultNamespace setting; none of these qualities are required or
have default values that are assumed if the quality is absent.
The namespace map is a map from short names for URIs to the namespace
URIs themselves.
The defaultNamespace setting selects one of the entries in the
namespace map by giving its short name. The associated URI (value of
this entry) becomes the default namespace for the SDF document.
+------------------+--------+-----------------------------------+
| Quality | Type | Description |
+------------------+--------+-----------------------------------+
| namespace | map | Defines short names mapped to |
| | | namespace URIs, to be used as |
| | | identifier prefixes |
| defaultNamespace | string | Identifies one of the prefixes in |
| | | the namespace map to be used as a |
| | | default in resolving identifiers |
+------------------+--------+-----------------------------------+
Table 2: Namespaces Block
The following example declares a set of namespaces and defines cap as
the default namespace. By convention, the values in the namespace
map contain full URIs without a fragment identifier, and the fragment
identifier is then added, if needed, where the namespace entry is
used.
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"namespace": {
"cap": "https://example.com/capability/cap",
"zcl": "https://zcl.example.com/sdf"
},
"defaultNamespace": "cap"
Multiple SDF documents can contribute to the same namespace by using
the same namespace URI for the default namespace across the
documents.
If no defaultNamespace setting is given, the SDF document does not
contribute to a global namespace (all definitions remain local to the
model and are not accessible for re-use by other models). As the
defaultNamespace is set by supplying a namespace short name, its
presence requires a namespace map that contains a mapping for that
namespace short name.
If no namespace map is given, no short names for namespace URIs are
set up, and no defaultNamespace can be given.
3.3. Definitions block
The Definitions block contains one or more groups, each identified by
a Class Name Keyword such as sdfObject or sdfProperty. There can
only be one group per keyword at this level; putting all the
individual definitions in the group under that keyword is just a
shortcut for identifying the class name keyword that applies to each
of them, without repeating it for each definition.
The value of each group is a JSON map, the keys of which serve for
naming the individual definitions in this group, and the
corresponding values provide a set of qualities (name-value pairs)
for the individual definition. (In short, these map entries are also
termed "named sets of qualities".)
Each group may contain zero or more definitions. Each identifier
defined creates a new type and term in the target namespace.
Declarations have a scope of the definition block they are directly
contained in.
A definition may in turn contain other definitions. Each definition
is a named set of qualities, i.e., it consists of the newly defined
identifier and a set of key-value pairs that represent the defined
qualities and contained definitions.
An example for an sdfObject definition is given in Figure 3:
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"sdfObject": {
"foo": {
"sdfProperty": {
"bar": {
"type": "boolean"
}
}
}
}
Figure 3: Example sdfObject definition
This example defines an sdfObject "foo" that is defined in the
default namespace (full address: #/sdfObject/foo), containing a
property that can be addressed as #/sdfObject/foo/sdfProperty/bar,
with data of type boolean.
Often, definitions are also declarations: the definition of the entry
"bar" in the property "foo" means that data corresponding to the
"foo" property in a property interaction offered by Thing can have
zero or one components modeled by "bar". Entries within sdfProperty,
sdfAction, and sdfEvent that are in turn within sdfObject or sdfThing
entries, are also declarations; entries within sdfData are not.
Similarly, sdfObject or sdfThing entries within an sdfThing
definition specify that the interactions offered by a Thing modeled
by this sdfThing include the interactions modeled by the nested
sdfObject or sdfThing.
3.4. Top-level Affordances and sdfData
Besides their placement within an sdfObject or sdfThing, affordances
(i.e., sdfProperty, sdfAction, and sdfEvent) as well as sdfData can
also be placed at the top level of an SDF document. Since they are
not associated with an sdfObject or sdfThing, these kinds of
definitions are intended to be re-used via the sdfRef mechanism (see
Section 4.4).
4. Names and namespaces
SDF documents may contribute to a global namespace, and may reference
elements from that global namespace. (An SDF document that does not
set a defaultNamespace does not contribute to a global namespace.)
4.1. Structure
Global names look exactly like https:// URIs with attached fragment
identifiers.
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There is no intention to require that these URIs can be dereferenced.
(However, as future extensions of SDF might find a use for
dereferencing global names, the URI should be chosen in such a way
that this may become possible in the future. See also
[I-D.bormann-t2trg-deref-id] for a discussion of dereferenceable
identifiers.)
The absolute-URI of a global name should be a URI as per Section 3 of
RFC 3986 [STD66], with a scheme of "https" and a path (hier-part in
[STD66]). For base SDF, the query part should not be used (it might
be used in extensions).
The fragment identifier is constructed as per Section 6 of [RFC6901].
4.2. Contributing global names
The fragment identifier part of a global name defined in an SDF
document is constructed from a JSON pointer that selects the element
defined for this name in the SDF document. The absolute-URI part is
a copy of the default namespace.
As a result, the default namespace is always the target namespace for
a name for which a definition is contributed. In order to emphasize
that name definitions are contributed to the default namespace, this
namespace is also termed the "target namespace" of the SDF document.
For instance, in Figure 1, definitions for the following global names
are contributed:
* https://example.com/capability/cap#/sdfObject/Switch
* https://example.com/capability/cap#/sdfObject/Switch/sdfProperty/
value
* https://example.com/capability/cap#/sdfObject/Switch/sdfAction/on
* https://example.com/capability/cap#/sdfObject/Switch/sdfAction/off
Note the #, which separates the absolute-URI part (Section 4.3 of RFC
3986 [STD66]) from the fragment identifier part (including the #, a
JSON Pointer as in Section 6 of [RFC6901]).
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4.3. Referencing global names
A name reference takes the form of the production curie in Section 3
of [W3C.NOTE-curie-20101216], but limiting the IRIs involved in that
grammar to URIs as per [STD66] and the prefixes to ASCII characters
[STD80]. (Note that this definition does not make use of the
production safe-curie in [W3C.NOTE-curie-20101216].)
A name that is contributed by the current SDF document can be
referenced by a Same-Document Reference as per Section 4.4 of RFC
3986 [STD66]. As there is little point in referencing the entire SDF
document, this will be a # followed by a JSON pointer. This is the
only kind of name reference to itself that is possible in an SDF
document that does not set a default namespace.
Name references that point outside the current SDF document need to
contain curie prefixes. These then reference namespace declarations
in the namespaces block.
For example, if a namespace prefix is defined:
"namespace": {
"foo": "https://example.com/"
}
Then this reference to that namespace:
"sdfRef": "foo:#/sdfData/temperatureData"
references the global name:
"https://example.com/#/sdfData/temperatureData"
Note that there is no way to provide a URI scheme name in a curie, so
all references to outside of the document need to go through the
namespace map.
Name references occur only in specific elements of the syntax of SDF:
* copying elements via sdfRef values
* pointing to elements via sdfRequired value elements
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4.4. sdfRef
In a JSON map establishing a definition, the keyword sdfRef is used
to copy the qualities and enclosed definitions of the referenced
definition, indicated by the included name reference, into the newly
formed definition. (This can be compared to the processing of the
$ref keyword in [JSO7].) The referenced definition should be such
that, after copying and applying the additional qualities in the
referencing definition, the newly built definition is also valid SDF
(e.g., the copied qualities and definitions are valid in the context
of the new definition).
For example, this reference:
"temperatureProperty": {
"sdfRef": "#/sdfData/temperatureData"
}
creates a new definition "temperatureProperty" that contains all of
the qualities defined in the definition at /sdfData/temperatureData.
The sdfRef member need not be the only member of a map. Additional
members may be present with the intention to override parts of the
referenced map or to add new qualities or definitions.
When processing sdfRef, if the target definition contains also sdfRef
(i.e., is based on yet another definition), that MUST be processed as
well.
More formally, for a JSON map that contains an sdfRef member, the
semantics is defined to be as if the following steps were performed:
1. The JSON map that contains the sdfRef member is copied into a
variable named "patch".
2. The sdfRef member of the copy in "patch" is removed.
3. the JSON pointer that is the value of the sdfRef member is
dereferenced and the result is copied into a variable named
"original".
4. The JSON Merge Patch algorithm [RFC7396] is applied to patch the
contents of "original" with the contents of "patch".
5. The result of the Merge Patch is used in place of the value of
the original JSON map.
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Note that the formal syntaxes given in Appendices A and B generally
describe the _result_ of applying a merge-patch: the notations are
not powerful enough to describe, for instance, how the merge-patch
algorithm causes null values within the sdfRef to remove members of
JSON maps from the referenced target. Nonetheless, the syntaxes also
give the syntax of the sdfRef itself, which vanishes during the
resolution; in many cases therefore even merge-patch inputs will
validate with these formal syntaxes.
Given the example (Figure 1), and the following definition:
{
"info": {
"title": "Example light switch using sdfRef"
},
"namespace": {
"cap": "https://example.com/capability/cap"
},
"defaultNamespace": "cap",
"sdfObject": {
"BasicSwitch": {
"sdfRef": "cap:#/sdfObject/Switch",
"sdfAction": {
"toggle": null
}
}
}
}
The resulting definition of the "BasicSwitch" sdfObject would be
identical to the definition of the "Switch" sdfObject except it would
not contain the "toggle" Action.
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{
"info": {
"title": "Example light switch using sdfRef"
},
"namespace": {
"cap": "https://example.com/capability/cap"
},
"defaultNamespace": "cap",
"sdfObject": {
"BasicSwitch": {
"sdfProperty": {
"value": {
"description":
"The state of the switch; false for off and true for on.",
"type": "boolean"
}
},
"sdfAction": {
"on": {
"description":
"Turn the switch on; equivalent to setting value to true."
},
"off": {
"description":
"Turn the switch off; equivalent to setting value to false."
}
}
}
}
}
4.4.1. Resolved models
A model where all sdfRef references are processed as described in
Section 4.4 is called a resolved model.
For example, given the following sdfData definitions:
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"sdfData": {
"Coordinate" : {
"type": "number", "unit": "m"
},
"X-Coordinate" : {
"sdfRef" : "#/sdfData/Coordinate",
"description":
"Distance from the base of the Thing along the X axis."
},
"Non-neg-X-Coordinate" : {
"sdfRef": "#/sdfData/X-Coordinate",
"minimum": 0
}
}
After resolving the definitions would look as follows:
"sdfData": {
"Coordinate" : {
"type": "number", "unit": "m"
},
"X-Coordinate" : {
"description":
"Distance from the base of the Thing along the X axis.",
"type": "number", "unit": "m"
},
"Non-neg-X-Coordinate" : {
"description":
"Distance from the base of the Thing along the X axis.",
"minimum": 0, "type": "number", "unit": "m"
}
}
4.5. sdfRequired
The keyword sdfRequired is provided to apply a constraint that
defines for which declarations the corresponding data are mandatory
in a grouping (sdfThing or sdfObject) modeled by the current
definition.
The value of sdfRequired is an array of references, each indicating
one or more declarations that are mandatory to be represented.
References in this array can be SDF names (JSON Pointers), or one of
two abbreviated reference formats:
* a text string with a "referenceable-name", namely an affordance
name or a grouping name:
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- All affordance declarations that are directly in the same
grouping (i.e., not nested further in another grouping) and
that carry this name are declared to be mandatory to be
represented. Note that there can be multiple such affordance
declarations, one per affordance type.
- The same applies to groupings made mandatory within groupings
containing them.
* the Boolean value true. The affordance or grouping itself that
carries the sdfRequired keyword is declared to be mandatory to be
represented.
Note that referenceable-names are not subject to the encoding JSON
pointers require as discussed in Section 2.3.2. To ensure that
referenceable-names are reliably distinguished from JSON pointers,
they are defined such that they cannot contain ":" or "#" characters
(see rule referenceable-name in Appendix A). (If these characters
are indeed contained in a Given Name, a JSON pointer needs to be
formed instead in order to reference it in "sdfRequired", potentially
requiring further path elements as well as JSON pointer encoding.
The need for this is best avoided by choosing Given Names without
these characters.)
The example in Figure 4 shows two required elements in the sdfObject
definition for "temperatureWithAlarm", the sdfProperty
"currentTemperature", and the sdfEvent "overTemperatureEvent". The
example also shows the use of JSON pointer with "sdfRef" to use a
pre-existing definition for the sdfProperty "currentTemperature" and
for the sdfOutputData produced by the sdfEvent
"overTemperatureEvent".
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"sdfObject": {
"temperatureWithAlarm": {
"sdfRequired": [
"#/sdfObject/temperatureWithAlarm/sdfProperty/currentTemperature",
"#/sdfObject/temperatureWithAlarm/sdfEvent/overTemperatureEvent"
],
"sdfData":{
"temperatureData": {
"type": "number"
}
},
"sdfProperty": {
"currentTemperature": {
"sdfRef": "#/sdfObject/temperatureWithAlarm/sdfData/temperatureData",
"writable": false
}
},
"sdfEvent": {
"overTemperatureEvent": {
"sdfOutputData": {
"sdfRef": "#/sdfObject/temperatureWithAlarm/sdfData/temperatureData"
}
}
}
}
}
Figure 4: Using sdfRequired
In Figure 4, the same sdfRequired can also be represented in short
form:
"sdfRequired": ["currentTemperature", "overTemperatureEvent"]
Or, for instance "overTemperatureEvent" could carry
"overTemperatureEvent": {
"sdfRequired": [true],
"...": "..."
}
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4.6. Common Qualities
Definitions in SDF share a number of qualities that provide metadata
for them. These are listed in Table 3. None of these qualities are
required or have default values that are assumed if the quality is
absent. If a short textual description is required for an
application and no label is given in the SDF model, in its place
applications could use the last part (the last reference-token,
Section 3 of [RFC6901]) of the JSON pointer to the definition.
+-------------+--------------+-----------------------------+
| Quality | Type | Description |
+-------------+--------------+-----------------------------+
| description | string | long text (no constraints) |
| label | string | short text (no constraints) |
| $comment | string | source code comments only, |
| | | no semantics |
| sdfRef | sdf-pointer | (see Section 4.4) |
| sdfRequired | pointer-list | (see Section 4.5, used in |
| | | affordances or groupings) |
+-------------+--------------+-----------------------------+
Table 3: Common Qualities
4.7. Data Qualities
Data qualities are used in sdfData and sdfProperty definitions, which
are named sets of data qualities (abbreviated as named-sdq).
These qualities include the common qualities, JSO-inspired qualities
(see below), and data qualities defined specifically for the present
specification; the latter are shown in Table 4. None of these
qualities are required or have default values that are assumed if the
quality is absent.
Appendix C lists data qualities inspired by the various proposals at
json-schema.org; the intention is that these (information model
level) qualities are compatible with the (data model) semantics from
the versions of the json-schema.org proposal they were imported from.
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+---------------+----------------+--------------------+---------+
| Quality | Type | Description | Default |
+---------------+----------------+--------------------+---------+
| (common) | | Section 4.6 | |
| unit | string | unit name (note 1) | N/A |
| nullable | boolean | indicates a null | true |
| | | value is available | |
| | | for this type | |
| contentFormat | string | content type (IANA | N/A |
| | | media type string | |
| | | plus parameters), | |
| | | encoding (note 2) | |
| sdfType | string | sdfType | N/A |
| | (Section | enumeration | |
| | 4.7.1) | (extensible) | |
| sdfChoice | named set of | named alternatives | N/A |
| | data qualities | | |
| | (Section | | |
| | 4.7.2) | | |
| enum | array of | abbreviation for | N/A |
| | strings | string-valued | |
| | | named alternatives | |
+---------------+----------------+--------------------+---------+
Table 4: SDF-defined Qualities of sdfData and sdfProperty
1. The unit name SHOULD be as per the SenML Units registry or the
Secondary Units registry in [IANA.senml] as specified by Sections
4.5.1 and 12.1 of [RFC8428] and Section 3 of [RFC8798],
respectively.
Exceptionally, if a registration in these registries cannot be
obtained or would be inappropriate, the unit name can also be a
URI that is pointing to a definition of the unit. Note that SDF
processors are not expected to, and normally SHOULD NOT,
dereference these URIs; the definition pointed to may be useful
to humans, though. (See [I-D.bormann-t2trg-deref-id] for a more
extensive discussion of dereferenceable identifiers).
A URI unit name is distinguished from a registered unit name by
the presence of a colon; any registered unit names that contain a
colon (at the time of writing, none) can therefore not be
directly used in SDF.
For use by translators into ecosystems that require URIs for unit
names, the URN sub-namespace "urn:ietf:params:unit" is provided
(Section 7.3). URNs from this sub-namespace MUST NOT be used in
a unit quality, in favor of simply notating the unit name (such
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as kg instead of urn:ietf:params:unit:kg), except where the unit
name contains a colon and can therefore not be directly used in
SDF.
2. The contentFormat quality follows the Content-Format-Spec as
defined in Section 6 of [RFC9193], allowing for expressing both
numeric and string based Content-Formats.
4.7.1. sdfType
SDF defines a number of basic types beyond those provided by JSON or
JSO. These types are identified by the sdfType quality, which is a
text string from a set of type names defined by the "sdfType values"
registry in the "Semantic Definition Format (SDF)" registry group
(Section 7.5.3). The sdfType name is composed of lower case ASCII
letters, digits, and - (ASCII hyphen/minus) characters, starting with
a lower case ASCII letter (i.e., using a pattern of
"[a-z][-a-z0-9]*"), typically employing kebab-case for names
constructed out of multiple words [KebabCase].
To aid interworking with JSO implementations, it is RECOMMENDED that
sdfType is always used in conjunction with the type quality inherited
from [JSO7V], in such a way as to yield a common representation of
the type's values in JSON.
Values for sdfType that are defined in this specification are shown
in Table 5. This table also gives a description of the semantics of
the sdfType, the conventional value for type to be used with the
sdfType value, and a conventional JSON representation for values of
the type. The type and the JSON representation are chosen to be
consistent with each other; this MUST be true for additionally
registered sdfType values as well.
+-------------+-------------+--------+----------------+------------+
| Name | Description | type | JSON | Reference |
| | | | Representation | |
+-------------+-------------+--------+----------------+------------+
| byte-string | A sequence | string | base64url | Section |
| | of zero or | | without | 3.4.5.2 of |
| | more bytes | | padding | RFC 8949 |
| | | | | [STD94] |
| unix-time | A point in | number | POSIX time | Section |
| | civil time | | | 3.4.2 of |
| | (note 1) | | | RFC 8949 |
| | | | | [STD94] |
+-------------+-------------+--------+----------------+------------+
Table 5: Values Defined in Base SDF for the sdfType Quality
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(1) Note that the definition of unix-time does not imply the
capability to represent points in time that fall on leap seconds.
More date/time-related sdfTypes are likely to be added in the sdfType
value registry.
4.7.2. sdfChoice
Data can be a choice of named alternatives, called sdfChoice. Each
alternative is identified by a name (string, key in the outer JSON
map used to represent the overall choice) and a set of dataqualities
(each in an inner JSON map, the value used to represent the
individual alternative in the outer JSON map). Dataqualities that
are specified at the same level as the sdfChoice apply to all choices
in the sdfChoice, except those specific choices where the dataquality
is overridden at the choice level.
sdfChoice merges the functions of two constructs found in [JSO7V]:
* enum
What could be expressed as
"enum": ["foo", "bar", "baz"]
in JSO, is often best represented as:
"sdfChoice": {
"foo": { "description": "This is a foonly"},
"bar": { "description":
"As defined in the second world congress"},
"baz": { "description": "From bigzee foobaz"}
}
This allows the placement of other dataqualities such as
description in the example.
If an enum needs to use a data type different from text string,
what would for instance have been:
"type": "number",
"enum": [1, 2, 3]
in JSO, is represented as:
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"type": "number",
"sdfChoice": {
"a-better-name-for-alternative-1": { "const": 1 },
"alternative-2": { "const": 2 },
"the-third-alternative": { "const": 3 }
}
where the string names obviously would be chosen in a way that is
descriptive for what these numbers actually stand for; sdfChoice
also makes it easy to add number ranges into the mix.
(Note that const can also be used for strings as in the previous
example, for instance, if the actual string value is indeed a
crucial element for the data model.)
* anyOf
JSO provides a type union called anyOf, which provides a choice
between anonymous alternatives.
What could have been in JSO:
"anyOf": [
{"type": "array", "minItems": 3, "maxItems": "3",
"items": {"$ref": "#/sdfData/rgbVal"}},
{"type": "array", "minItems": 4, "maxItems": "4",
"items": {"$ref": "#/sdfData/cmykVal"}}
]
can be more descriptively notated in SDF as:
"sdfChoice": {
"rgb": {"type": "array", "minItems": 3, "maxItems": "3",
"items": {"sdfRef": "#/sdfData/rgbVal"}},
"cmyk": {"type": "array", "minItems": 4, "maxItems": "4",
"items": {"sdfRef": "#/sdfData/cmykVal"}}
}
Note that there is no need in SDF for the type intersection construct
allOf or the peculiar type-xor construct oneOf found in [JSO7V].
As a simplification for users of SDF models who are accustomed to the
JSO enum keyword, this is retained, but limited to a choice of text
string values, such that
"enum": ["foo", "bar", "baz"]
is syntactic sugar for
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"sdfChoice": {
"foo": { "const": "foo"},
"bar": { "const": "bar"},
"baz": { "const": "baz"}
}
In a single definition, the keyword enum cannot be used at the same
time as the keyword sdfChoice, as the former is just syntactic sugar
for the latter.
5. Keywords for definition groups
The following SDF keywords are used to create definition groups in
the target namespace. All these definitions share some common
qualities as discussed in Section 4.6.
5.1. sdfObject
The sdfObject keyword denotes a group of zero or more sdfObject
definitions. sdfObject definitions may contain or include definitions
of named Properties, Actions, Events declared for the sdfObject, as
well as named data types (sdfData group) to be used in this or other
sdfObjects.
The qualities of an sdfObject include the common qualities;
additional qualities are shown in Table 6. None of these qualities
are required or have default values that are assumed if the quality
is absent.
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+-------------+-----------+--------------------------------+
| Quality | Type | Description |
+-------------+-----------+--------------------------------+
| (common) | | Section 4.6 |
| sdfProperty | property | zero or more named property |
| | | definitions for this sdfObject |
| sdfAction | action | zero or more named action |
| | | definitions for this sdfObject |
| sdfEvent | event | zero or more named event |
| | | definitions for this sdfObject |
| sdfData | named-sdq | zero or more named data type |
| | | definitions that might be used |
| | | in the above |
| minItems | number | (array) Minimum number of |
| | | multiplied affordances in |
| | | array |
| maxItems | number | (array) Maximum number of |
| | | multiplied affordances in |
| | | array |
+-------------+-----------+--------------------------------+
Table 6: Qualities of sdfObject
5.2. sdfProperty
The sdfProperty keyword denotes a group of zero or more Property
definitions.
Properties are used to model elements of state.
The qualities of a Property definition include the data qualities
(and thus the common qualities), see Section 4.7, additional
qualities are shown in Table 7.
+------------+---------+-------------------------------+---------+
| Quality | Type | Description | Default |
+------------+---------+-------------------------------+---------+
| (data) | | Section 4.7 | |
| readable | boolean | Reads are allowed | true |
| writable | boolean | Writes are allowed | true |
| observable | boolean | flag to indicate asynchronous | true |
| | | notification is available | |
+------------+---------+-------------------------------+---------+
Table 7: Qualities of sdfProperty
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5.3. sdfAction
The sdfAction keyword denotes a group of zero or more Action
definitions.
Actions are used to model commands and methods which are invoked.
Actions may have parameter data that are supplied upon invocation and
output data that is provided as a direct result of the invocation of
the action (note that "action objects" may also be created to furnish
ongoing information during a long-running action; these would be
pointed to by the output data).
The qualities of an Action definition include the common qualities,
additional qualities are shown in Table 8.
+---------------+-----------+----------------------------+
| Quality | Type | Description |
+---------------+-----------+----------------------------+
| (common) | | Section 4.6 |
| sdfInputData | map | data qualities of the |
| | | input data for an Action |
| sdfOutputData | map | data qualities of the |
| | | output data for an Action |
| sdfData | named-sdq | zero or more named data |
| | | type definitions that |
| | | might be used in the above |
+---------------+-----------+----------------------------+
Table 8: Qualities of sdfAction
sdfInputData defines the input data of the action. sdfOutputData
defines the output data of the action. As discussed in
Section 2.2.3, a set of data qualities with type "object" can be used
to substructure either data item, with optionality indicated by the
data quality required.
5.4. sdfEvent
The sdfEvent keyword denotes zero or more Event definitions.
Events are used to model asynchronous occurrences that may be
communicated proactively. Events have data elements which are
communicated upon the occurrence of the event.
The qualities of sdfEvent include the common qualities, additional
qualities are shown in Table 9.
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+---------------+-----------+----------------------------+
| Quality | Type | Description |
+---------------+-----------+----------------------------+
| (common) | | Section 4.6 |
| sdfOutputData | map | data qualities of the |
| | | output data for an Event |
| sdfData | named-sdq | zero or more named data |
| | | type definitions that |
| | | might be used in the above |
+---------------+-----------+----------------------------+
Table 9: Qualities of sdfEvent
sdfOutputData defines the output data of the action. As discussed in
Section 2.2.4, a set of data qualities with type "object" can be used
to substructure the output data item, with optionality indicated by
the data quality required.
5.5. sdfData
The sdfData keyword denotes a group of zero or more named data type
definitions (named-sdq).
An sdfData definition provides a reusable semantic identifier for a
type of data item and describes the constraints on the defined type.
sdfData is not itself a declaration, so it does not cause any of
these data items to be included in an affordance definition.
The qualities of sdfData include the data qualities (and thus the
common qualities), see Section 4.7.
6. High Level Composition
The requirements for high level composition include the following:
* The ability to represent products, standardized product types, and
modular products while maintaining the atomicity of sdfObjects.
* The ability to compose a reusable definition block from
sdfObjects. Example: a single plug unit of an outlet strip with
sdfObjects for on/off control, energy monitor, and optional
dimmer, while retaining the atomicity of the individual
sdfObjects.
* The ability to compose sdfObjects and other definition blocks into
a higher level sdfThing that represents a product, while retaining
the atomicity of sdfObjects.
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* The ability to enrich and refine a base definition to have
product-specific qualities and quality values, such as unit,
range, and scale settings.
* The ability to reference items in one part of a complex definition
from another part of the same definition. Example: summarizing
the energy readings from all plugs in an outlet strip.
6.1. Paths in the model namespaces
The model namespace is organized according to terms that are defined
in the SDF documents that contribute to the namespace. For example,
definitions that originate from an organization or vendor are
expected to be in a namespace that is specific to that organization
or vendor.
The structure of a path in a namespace is defined by the JSON
Pointers to the definitions in the SDF documents in that namespace.
For example, if there is an SDF document defining an sdfObject
"Switch" with an action "on", then the reference to the action would
be "ns:#/sdfObject/Switch/sdfAction/on" where ns is the namespace
prefix (short name for the namespace).
6.2. Modular Composition
Modular composition of definitions enables an existing definition
(could be in the same or another SDF document) to become part of a
new definition by including a reference to the existing definition
within the model namespace.
6.2.1. Use of the "sdfRef" keyword to re-use a definition
An existing definition may be used as a template for a new
definition, that is, a new definition is created in the target
namespace which uses the defined qualities of some existing
definition. This pattern uses the keyword sdfRef as a quality of a
new definition with a value consisting of a reference to the existing
definition that is to be used as a template.
In the definition that uses sdfRef, new qualities may be added and
existing qualities from the referenced definition may be overridden.
(Note that JSON maps do not have a defined order, so the SDF
processor may see these overrides before seeing the sdfRef.)
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Note that the definition referenced by sdfRef might contain qualities
or definitions that are not valid in the context where the sdfRef is
used. In this case, the resulting model, when resolved, may be
invalid. Example: an sdfRef adds an sdfThing definition in an
sdfObject definition.
As a convention, overrides are intended to be used only for further
restricting the allowable set of data values. Such a usage is shown
in Figure 5: any value allowable for a cable-length also is an
allowable value for a length, with the additional restriction that
the length cannot be smaller than 5 cm. (This is labeled as a
convention as it cannot be checked in the general case. A quality of
implementation consideration for a tool might be to provide at least
some form of checking.) Note that the example provides a description
that overrides the description of the referenced definition; as this
quality is intended for human consumption there is no conflict with
the intended goal.
"sdfData":
"length" : {
"type": "number",
"minimum": 0,
"unit": "m"
"description": "There can be no negative lengths."
}
...
"cable-length" : {
"sdfRef": "#/sdfData/length"
"minimum": 5e-2,
"description": "Cables must be at least 5 cm."
}
Figure 5: Using an Override to Further Restrict the Set of Data
Values
6.3. sdfThing
An sdfThing is a set of declarations and qualities that may be part
of a more complex model. For example, the sdfObject declarations
that make up the definition of a single socket of an outlet strip
could be encapsulated in an sdfThing, which itself could be used in a
declaration in the sdfThing definition for the outlet strip. (See
Figure 7 in Appendix D.1 for parts of an SDF model for this example).
sdfThing definitions carry semantic meaning, such as a defined
refrigerator compartment and a defined freezer compartment, making up
a combination refrigerator-freezer product. An sdfThing may be
composed of sdfObjects and other sdfThings. It can also contain
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sdfData definitions, as well as declarations of interaction
affordances itself, such as a status (on/off) for the refrigerator-
freezer as a whole (see Figure 8 in Appendix D.2 for an example SDF
model illustrating these aspects).
The qualities of sdfThing are shown in Table 10. Analogous to
sdfObject, the presence of one or both of the optional qualities
"minItems" and "maxItems" defines the sdfThing as an array.
+-------------+-----------+-----------------------------+
| Quality | Type | Description |
+-------------+-----------+-----------------------------+
| (common) | | Section 4.6 |
| sdfThing | thing | |
| sdfObject | object | |
| sdfProperty | property | zero or more named property |
| | | definitions for this thing |
| sdfAction | action | zero or more named action |
| | | definitions for this thing |
| sdfEvent | event | zero or more named event |
| | | definitions for this thing |
| sdfData | named-sdq | zero or more named data |
| | | type definitions that might |
| | | be used in the above |
| minItems | number | (array) Minimum number of |
| | | multiplied affordances in |
| | | array |
| maxItems | number | (array) Maximum number of |
| | | multiplied affordances in |
| | | array |
+-------------+-----------+-----------------------------+
Table 10: Qualities of sdfThing
7. IANA Considerations
// RFC Ed.: throughout this section, please replace RFC XXXX with
// this RFC number, and remove this note.
7.1. Media Type
IANA is requested to add the following Media-Type to the "Media
Types" registry [IANA.media-types].
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+----------+----------------------+-----------------------+
| Name | Template | Reference |
+----------+----------------------+-----------------------+
| sdf+json | application/sdf+json | RFC XXXX, Section 7.1 |
+----------+----------------------+-----------------------+
Table 11: Media Type Registration for SDF
Type name: application
Subtype name: sdf+json
Required parameters: N/A
Optional parameters: N/A
Encoding considerations: binary (JSON is UTF-8-encoded text)
Security considerations: Section 8 of RFC XXXX
Interoperability considerations: none
Published specification: Section 7.1 of RFC XXXX
Applications that use this media type: Tools for data and
interaction modeling in the Internet of Things and related
environments
Fragment identifier considerations: A JSON Pointer fragment
identifier may be used, as defined in Section 6 of [RFC6901].
Additional information: Magic number(s): n/a
File extension(s): .sdf.json
Windows Clipboard Name: "Semantic
Definition Format (SDF) for Data and Interactions of Things"
Macintosh file type code(s): n/a
Macintosh Universal Type Identifier code: o
rg.ietf.sdf-json
conforms to public.text
Person & email address to contact for further information: ASDF WG
mailing list (asdf@ietf.org), or IETF Applications and Real-Time
Area (art@ietf.org)
Intended usage: COMMON
Restrictions on usage: none
Author/Change controller: IETF
Provisional registration: no
7.2. Content-Format
This document adds the following Content-Format to the "CoAP Content-
Formats" registry, within the "Constrained RESTful Environments
(CoRE) Parameters" registry group [IANA.core-parameters], where 434
comes from the "IETF Review" 256-999 range.
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+----------------------+----------------+-----+-----------+
| Content Type | Content Coding | ID | Reference |
+----------------------+----------------+-----+-----------+
| application/sdf+json | - | 434 | RFC XXXX |
+----------------------+----------------+-----+-----------+
Table 12: SDF Content-format Registration
// RFC Ed.: 434 was earmarked in
https://mailarchive.ietf.org/arch/msg/core-parameters/
iLDsdxk80YO9IsLMXMAgcx5S8Ak/ (https://mailarchive.ietf.org/arch/msg/
core-parameters/iLDsdxk80YO9IsLMXMAgcx5S8Ak/); please replace 434
with the assigned ID, remove the requested range, and remove this
note.
// RFC Ed.: please replace RFC XXXX with this RFC number and remove
this note.
7.3. IETF URN Sub-namespace for Unit Names (urn:ietf:params:unit)
IANA is requested to register the following value in the "IETF URN
Sub-namespace for Registered Protocol Parameter Identifiers" registry
in [IANA.params], following the template in [BCP73]:
Registry name: unit
Specification: RFC XXXX
Repository: combining the symbol values from the SenML Units
registry and the Secondary Units registry in [IANA.senml] as
specified by Sections 4.5.1 and 12.1 of [RFC8428] and Section 3 of
[RFC8798], respectively (which by the registration policy are
guaranteed to be non-overlapping).
Index value: Percent-encoding (Section 2.1 of RFC 3986 [STD66]) is
required of any characters in unit names except for the set
"unreserved" (Section 2.3 of RFC 3986 [STD66]), the set "sub-
delims" (Section 2.3 of RFC 3986 [STD66]), ":" or "@" (i.e., the
result must match the ABNF rule "pchar" in Section 3.3 of RFC 3986
[STD66]).
7.4. SenML registry group
IANA is requested to add the following note to the SenML registry
group [IANA.senml]:
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| In SDF [RFC XXXX], a URI unit name is distinguished from a
| registered unit name by the presence of a colon; any registered
| unit name that contains a colon can therefore not be directly used
| in SDF.
7.5. Registries
IANA is requested to create a "Semantic Definition Format (SDF)"
registry group, with the registries defined in this Section.
7.5.1. Quality Names
IANA is requested to create a "Quality Names" registry in the
"Semantic Definition Format (SDF)" registry group, with the following
template:
Name: A quality name composed of ASCII letters, digits, and dollar
signs, starting with a lower case ASCII letter or a dollar sign
(i.e., using a pattern of "[a-z$][A-Za-z$0-9]*").
Brief Description: A brief description.
Reference: A pointer to a specification.
Change Controller: (see Section 2.3 of RFC 8126 [BCP26])
Quality Names in this registry are intended to be registered in
conjunction with RFCs and activities of the IETF.
The registration policy is Specification Required as per Section 4.6
of RFC 8126 [BCP26]. (Note that the policy is not "RFC Required" or
"IETF Review" Sections 4.7 and 4.8 of RFC 8126 [BCP26] so that
registrations can be made earlier in the process, even earlier than
foreseen in [BCP100].)
The instructions to the Experts are:
* to ascertain that the specification is available in an immutable
reference and has achieved a good level of review in conjunction
with RFCs or activities of the IETF, and
* to be frugal in the allocation of quality names that are
suggestive of generally applicable semantics, keeping them in
reserve for qualities that are likely to enjoy wide use and can
make good use of their conciseness.
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The "Quality Names" registry starts out as in Table 13; all
references for these initial entries are to RFC XXXX and all change
controllers are given as "IETF"".
+----------------------+------------------------------------------+
| Name | Brief Description |
+----------------------+------------------------------------------+
| $comment | source code comments only, no semantics |
| const | constant value |
| contentFormat | content format |
| default | default value |
| description | long description text |
| enum | sdfChoice limited to text strings |
| exclusiveMaximum | exclusive maximum for a number |
| exclusiveMinimum | exclusive minimum for a number |
| format | specific format for a text string |
| items | items of an array |
| label | short text (no constraints); defaults to |
| | key |
| maxItems | maximum number of items in an array |
| maxLength | maximum length for a text string (in |
| | characters, i.e., Unicode scalar values) |
| maximum | maximum for a number |
| minItems | minimum number of items in an array |
| minLength | minimum length for a text string (in |
| | characters, i.e., Unicode scalar values) |
| minimum | minimum for a number |
| multipleOf | step size of number |
| nullable | boolean: can the item be left out? |
| observable | boolean: can the item be observed? |
| pattern | regular expression pattern for a text |
| | string |
| properties | named dataqualities for type="object" |
| readable | boolean: can the item be read? |
| required | which data items are required? |
| sdfChoice | named dataqualities for a choice |
| sdfData | named dataqualities for an independent |
| | data type definition |
| sdfInputData | input data to an action |
| sdfOutputData | output data of an action or event |
| | (sdfRequired applies here) |
| sdfRef | sdf-pointer to definition being |
| | referenced |
| sdfRequired | pointer-list to declarations of required |
| | components |
| sdfRequiredInputData | pointer-list to declarations of required |
| | input data for an action |
| sdfType | more detailed information about the type |
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| | of a string |
| type | general category of data type |
| uniqueItems | boolean: do the items of the array need |
| | to be all different? |
| unit | engineering unit and scale (per SenML |
| | registry) |
| writable | boolean: can the item be written to? |
+----------------------+------------------------------------------+
Table 13: Initial Content of Quality Names Registry
7.5.2. Quality Name Prefixes
IANA is requested to create a "Quality Name Prefixes" registry in the
"Semantic Definition Format (SDF)" registry group, with the following
template:
Prefix: A quality name prefix composed of lower case ASCII letters
and digits, starting with a lower case ASCII letter (i.e., using a
pattern of "[a-z][a-z0-9]*").
Contact: A contact point for the organization that assigns quality
names with this prefix.
Reference: A pointer to additional information, if available.
Quality Name Prefixes are intended to be registered by organizations
that plan to define quality names constructed with an organization-
specifix prefix (Section 2.3.3).
The registration policy is Expert Review as per Section 4.5 of RFC
8126 [BCP26]. The instructions to the Expert are to ascertain that
the organization will handle quality names constructed using their
prefix in a way that roughly achieves the objectives for an IANA
registry that support interoperability of SDF models employing these
quality names, including:
* Stability, "stable and permanent";
* Transparency, "readily available", "in sufficient detail"
(Section 4.6 of RFC 8126 [BCP26]).
The "Quality Name Prefixes" registry starts out empty.
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7.5.3. sdfType Values
IANA is requested to create a "sdfType values" registry in the
"Semantic Definition Format (SDF)" registry group, with the following
template:
Name: A name composed of lower case ASCII letters, digits and -
(ASCII hyphen/minus) characters, starting with a lower case ASCII
letter (i.e., using a pattern of "[a-z][-a-z0-9]*").
Description: A short description of the information model level
structure and semantics
type: The value of the quality "type" to be used with this sdfType
JSON Representation A short description of a JSON representation
that can be used for this sdfType. As per Section 4.7.1, this
MUST be consistent with the type.
Reference: A more detailed specification of meaning and use of
sdfType.
sdfType values are intended to be registered to enable modeling
additional SDF-specific types (see Section 4.7.1).
The registration policy is Specification Required as per Section 4.6
of RFC 8126 [BCP26]. The instructions to the Expert are to ascertain
that the specification provides enough detail to enable
interoperability between implementations of the sdfType being
registered, and that names are chosen with enough specificity that
ecosystem-specific sdfTypes will not be confused with more generally
applicable ones.
The initial set of registrations is described in Table 5.
7.5.4. Feature Names
IANA is requested to create a "Feature Names" registry in the
"Semantic Definition Format (SDF)" registry group, with the following
template:
Name: A feature name composed of ASCII letters, digits, and dollar
signs, starting with a lower case ASCII letter or a dollar sign
(i.e., using a pattern of "[a-z$][A-Za-z$0-9]*").
Brief Description: A brief description.
Reference: A pointer to a specification.
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Change Controller: (see Section 2.3 of RFC 8126 [BCP26])
The registration policy is Specification Required as per Section 4.6
of RFC 8126 [BCP26].
The instructions to the Experts are:
* to ascertain that the specification is available in an immutable
reference and has achieved a good level of review, and
* to be frugal in the allocation of feature names that are
suggestive of generally applicable semantics, keeping them in
reserve for features that are likely to enjoy wide use and can
make good use of their conciseness.
The "Feature Names" registry starts out empty.
8. Security Considerations
Some wider security considerations applicable to Things are discussed
in [RFC8576].
Section 5 of [RFC8610] gives an overview over security considerations
that arise when formal description techniques are used to govern
interoperability; analogs of these security considerations can apply
to SDF.
The security considerations of underlying building blocks such as
those detailed in Section 10 of RFC 3629 [STD63] apply.
SDF uses JSON as a representation language. For a number of cases,
[STD90] indicates that implementation behavior for certain constructs
allowed by the JSON grammar is unpredictable.
Implementations need to be robust against invalid or unpredictable
cases on input, preferably by rejecting input that is invalid or that
would lead to unpredictable behavior, and need to avoid generating
these cases on output.
Implementations of model languages may also exhibit performance-
related availability issues when the attacker can control the input,
see Section 4.1 of [RFC9535] for a brief discussion and Section 8 of
[RFC9485] for considerations specific to the use of pattern.
SDF may be used in two processes that are often security relevant:
model-based _validation_ of data that is intended to be described by
SDF models, and model-based _augmentation_ of these data with
information obtained from the SDF models that apply.
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Implementations need to ascertain the provenance (and thus
authenticity and integrity) and applicability of the SDF models they
employ operationally in such security relevant ways. Implementations
that make use of the composition mechanisms defined in this document
need to do this for each of the components they combine into the SDF
models they employ. Essentially, this process needs to undergo the
same care and scrutiny as any other introduction of source code into
a build environment; the possibility of supply-chain attacks on the
modules imported needs to be considered.
Specifically, implementations might rely on model-based input
validation for enforcing certain properties of the data structure
ingested (which, if not validated, could lead to malfunctions such as
crashes and remote code execution). These implementations need to be
particularly careful about the data models they apply, including
their provenance and potential changes of these properties that
upgrades to the referenced modules may (inadvertently or as part of
an attack) cause. More generally speaking, implementations should
strive to be robust against expected and unexpected limitations of
the model-based input validation mechanisms and their
implementations.
Similarly, implementations that rely on model-based augmentation may
generate false data from their inputs; this is an integrity violation
in any case but also can possibly be exploited for further attacks.
In applications that dynamically acquire models and obtain modules
from module references in these, the security considerations of
dereferenceable identifiers apply (see [I-D.bormann-t2trg-deref-id]
for a more extensive discussion of dereferenceable identifiers).
There may be confidentiality requirements on SDF models, both on
their content and on the fact that a specific model is used in a
particular Thing or environment. The present specification does not
discuss model discovery or define an access control model for SDF
models, nor does it define a way to obtain selective disclosure where
that may be required. It is likely that these definitions require
additional context from underlying ecosystems and the characteristics
of the protocols employed there; this is therefore left as future
work (e.g., for documents such as [I-D.bormann-asdf-sdf-mapping]).
9. References
9.1. Normative References
[BCP14] Best Current Practice 14,
<https://www.rfc-editor.org/info/bcp14>.
At the time of writing, this BCP comprises the following:
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Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[BCP26] Best Current Practice 26,
<https://www.rfc-editor.org/info/bcp26>.
At the time of writing, this BCP comprises the following:
Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[BCP73] Best Current Practice 73,
<https://www.rfc-editor.org/info/bcp73>.
At the time of writing, this BCP comprises the following:
Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An
IETF URN Sub-namespace for Registered Protocol
Parameters", BCP 73, RFC 3553, DOI 10.17487/RFC3553, June
2003, <https://www.rfc-editor.org/info/rfc3553>.
[IANA.core-parameters]
IANA, "Constrained RESTful Environments (CoRE)
Parameters",
<https://www.iana.org/assignments/core-parameters>.
[IANA.media-types]
IANA, "Media Types",
<https://www.iana.org/assignments/media-types>.
[IANA.params]
IANA, "Uniform Resource Name (URN) Namespace for IETF
Use", <https://www.iana.org/assignments/params>.
[IANA.senml]
IANA, "Sensor Measurement Lists (SenML)",
<https://www.iana.org/assignments/senml>.
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
<https://www.rfc-editor.org/rfc/rfc3339>.
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[RFC6901] Bryan, P., Ed., Zyp, K., and M. Nottingham, Ed.,
"JavaScript Object Notation (JSON) Pointer", RFC 6901,
DOI 10.17487/RFC6901, April 2013,
<https://www.rfc-editor.org/rfc/rfc6901>.
[RFC7396] Hoffman, P. and J. Snell, "JSON Merge Patch", RFC 7396,
DOI 10.17487/RFC7396, October 2014,
<https://www.rfc-editor.org/rfc/rfc7396>.
[RFC8428] Jennings, C., Shelby, Z., Arkko, J., Keranen, A., and C.
Bormann, "Sensor Measurement Lists (SenML)", RFC 8428,
DOI 10.17487/RFC8428, August 2018,
<https://www.rfc-editor.org/rfc/rfc8428>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/rfc/rfc8610>.
[RFC8798] Bormann, C., "Additional Units for Sensor Measurement
Lists (SenML)", RFC 8798, DOI 10.17487/RFC8798, June 2020,
<https://www.rfc-editor.org/rfc/rfc8798>.
[RFC9165] Bormann, C., "Additional Control Operators for the Concise
Data Definition Language (CDDL)", RFC 9165,
DOI 10.17487/RFC9165, December 2021,
<https://www.rfc-editor.org/rfc/rfc9165>.
[RFC9193] Keränen, A. and C. Bormann, "Sensor Measurement Lists
(SenML) Fields for Indicating Data Value Content-Format",
RFC 9193, DOI 10.17487/RFC9193, June 2022,
<https://www.rfc-editor.org/rfc/rfc9193>.
[RFC9562] Davis, K., Peabody, B., and P. Leach, "Universally Unique
IDentifiers (UUIDs)", RFC 9562, DOI 10.17487/RFC9562, May
2024, <https://www.rfc-editor.org/rfc/rfc9562>.
[SPDX] "SPDX License List", <https://spdx.org/licenses/>.
[STD63] Internet Standard 63,
<https://www.rfc-editor.org/info/std63>.
At the time of writing, this STD comprises the following:
Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <https://www.rfc-editor.org/info/rfc3629>.
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[STD66] Internet Standard 66,
<https://www.rfc-editor.org/info/std66>.
At the time of writing, this STD comprises the following:
Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[STD80] Internet Standard 80,
<https://www.rfc-editor.org/info/std80>.
At the time of writing, this STD comprises the following:
Cerf, V., "ASCII format for network interchange", STD 80,
RFC 20, DOI 10.17487/RFC0020, October 1969,
<https://www.rfc-editor.org/info/rfc20>.
[STD90] Internet Standard 90,
<https://www.rfc-editor.org/info/std90>.
At the time of writing, this STD comprises the following:
Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>.
[STD94] Internet Standard 94,
<https://www.rfc-editor.org/info/std94>.
At the time of writing, this STD comprises the following:
Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/info/rfc8949>.
[W3C.NOTE-curie-20101216]
Birbeck, M., Ed. and S. McCarron, Ed., "CURIE Syntax 1.0",
W3C NOTE NOTE-curie-20101216, W3C NOTE-curie-20101216, 16
December 2010,
<https://www.w3.org/TR/2010/NOTE-curie-20101216/>.
9.2. Informative References
[BCP100] Best Current Practice 100,
<https://www.rfc-editor.org/info/bcp100>.
At the time of writing, this BCP comprises the following:
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Cotton, M., "Early IANA Allocation of Standards Track Code
Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January
2014, <https://www.rfc-editor.org/info/rfc7120>.
[CamelCase]
"Camel Case", December 2014,
<http://wiki.c2.com/?CamelCase>.
[ECMA-262] Ecma International, "ECMAScript 2020 Language
Specification", ECMA Standard ECMA-262, 11th Edition, June
2020, <https://www.ecma-international.org/wp-
content/uploads/ECMA-262.pdf>.
[I-D.bormann-asdf-sdf-mapping]
Bormann, C. and J. Romann, "Semantic Definition Format
(SDF): Mapping files", Work in Progress, Internet-Draft,
draft-bormann-asdf-sdf-mapping-05, 6 December 2024,
<https://datatracker.ietf.org/doc/html/draft-bormann-asdf-
sdf-mapping-05>.
[I-D.bormann-asdf-sdftype-link]
Bormann, C., "An sdfType for Links", Work in Progress,
Internet-Draft, draft-bormann-asdf-sdftype-link-04, 6
December 2024, <https://datatracker.ietf.org/doc/html/
draft-bormann-asdf-sdftype-link-04>.
[I-D.bormann-t2trg-deref-id]
Bormann, C. and C. Amsüss, "The "dereferenceable
identifier" pattern", Work in Progress, Internet-Draft,
draft-bormann-t2trg-deref-id-05, 3 March 2025,
<https://datatracker.ietf.org/doc/html/draft-bormann-
t2trg-deref-id-05>.
[I-D.irtf-t2trg-rest-iot]
Keränen, A., Kovatsch, M., and K. Hartke, "Guidance on
RESTful Design for Internet of Things Systems", Work in
Progress, Internet-Draft, draft-irtf-t2trg-rest-iot-15, 21
October 2024, <https://datatracker.ietf.org/doc/html/
draft-irtf-t2trg-rest-iot-15>.
[JSO4] Galiegue, F., Zyp, K., and G. Court, "JSON Schema: core
definitions and terminology", Work in Progress, Internet-
Draft, draft-zyp-json-schema-04, 31 January 2013,
<https://datatracker.ietf.org/doc/html/draft-zyp-json-
schema-04>. This is the base specification for json-
schema.org "draft 4".
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[JSO4V] Zyp, K. and G. Court, "JSON Schema: interactive and non
interactive validation", Work in Progress, Internet-Draft,
draft-fge-json-schema-validation-00, 31 January 2013,
<https://datatracker.ietf.org/doc/html/draft-fge-json-
schema-validation-00>. This is the validation
specification for json-schema.org "draft 4".
[JSO7] Wright, A. and H. Andrews, "JSON Schema: A Media Type for
Describing JSON Documents", Work in Progress, Internet-
Draft, draft-handrews-json-schema-01, 19 March 2018,
<https://datatracker.ietf.org/doc/html/draft-handrews-
json-schema-01>. This is the base specification for json-
schema.org "draft 7".
[JSO7V] Wright, A., Andrews, H., and G. Luff, "JSON Schema
Validation: A Vocabulary for Structural Validation of
JSON", Work in Progress, Internet-Draft, draft-handrews-
json-schema-validation-01, 19 March 2018,
<https://datatracker.ietf.org/doc/html/draft-handrews-
json-schema-validation-01>. This is the validation
specification for json-schema.org "draft 7".
[KebabCase]
"Kebab Case", August 2014,
<http://wiki.c2.com/?KebabCase>.
[OCF] "OCF Resource Type Specification",
<https://openconnectivity.org/specs/
OCF_Resource_Type_Specification.pdf>.
[OMA] "OMA LightweightM2M (LwM2M) Object and Resource Registry",
<http://www.openmobilealliance.org/wp/omna/lwm2m/
lwm2mregistry.html>.
[RFC8576] Garcia-Morchon, O., Kumar, S., and M. Sethi, "Internet of
Things (IoT) Security: State of the Art and Challenges",
RFC 8576, DOI 10.17487/RFC8576, April 2019,
<https://www.rfc-editor.org/rfc/rfc8576>.
[RFC9485] Bormann, C. and T. Bray, "I-Regexp: An Interoperable
Regular Expression Format", RFC 9485,
DOI 10.17487/RFC9485, October 2023,
<https://www.rfc-editor.org/rfc/rfc9485>.
[RFC9535] Gössner, S., Ed., Normington, G., Ed., and C. Bormann,
Ed., "JSONPath: Query Expressions for JSON", RFC 9535,
DOI 10.17487/RFC9535, February 2024,
<https://www.rfc-editor.org/rfc/rfc9535>.
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[STD97] Internet Standard 97,
<https://www.rfc-editor.org/info/std97>.
At the time of writing, this STD comprises the following:
Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", STD 97, RFC 9110,
DOI 10.17487/RFC9110, June 2022,
<https://www.rfc-editor.org/info/rfc9110>.
[WoT] Kaebisch, S., McCool, M., and E. Korkan, "Web of Things
(WoT) Thing Description 1.1", W3C Recommendation, 5
December 2023,
<https://www.w3.org/TR/wot-thing-description11/>.
[ZCL] "The ZigBee Cluster Library", Elsevier, Zigbee Wireless
Networking pp. 239-271,
DOI 10.1016/b978-0-7506-8597-9.00006-9,
ISBN ["9780750685979"], 2008,
<https://doi.org/10.1016/b978-0-7506-8597-9.00006-9>.
Appendix A. Formal Syntax of SDF
This normative appendix describes the syntax of SDF using CDDL
[RFC8610].
This appendix shows the framework syntax only, i.e., a syntax with
liberal extension points. Since this syntax is nearly useless in
finding typos in an SDF specification, a second syntax, the
validation syntax, is defined that does not include the extension
points. The validation syntax can be generated from the framework
syntax by leaving out all lines containing the string EXTENSION-
POINT; as this is trivial, the result is not shown here.
This appendix makes use of CDDL "features" as defined in Section 4 of
[RFC9165]. Features whose names end in "-ext" indicate extension
points for further evolution.
start = sdf-syntax
sdf-syntax = {
; info will be required in most process policies
? info: sdfinfo
? namespace: named<text>
? defaultNamespace: text
; Thing is a composition of objects that work together in some way
? sdfThing: named<thingqualities>
; Object is a set of Properties, Actions, and Events that together
; perform a particular function
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? sdfObject: named<objectqualities>
; Includes Properties, Actions, and Events as well as sdfData
paedataqualities
EXTENSION-POINT<"top-ext">
}
sdfinfo = {
? title: text
? description: text
? version: text
? copyright: text
? license: text
? modified: modified-date-time
? features: [
* (any .feature "feature-name") ; EXTENSION-POINT
]
optional-comment
EXTENSION-POINT<"info-ext">
}
; Shortcut for a map that gives names to instances of X
; (has keys of type text and values of type X)
named<X> = { * text => X }
; EXTENSION-POINT is only used in framework syntax
EXTENSION-POINT<f> = ( * (quality-name .feature f) => any )
quality-name = text .regexp "([a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*"
sdf-pointer = global / same-object / true
global = text .regexp ".*[:#].*" ; rough CURIE or JSON Pointer syntax
same-object = referenceable-name
referenceable-name = text .regexp "[^:#]*"
; per se no point in having an empty list, but used for sdfRequired
; in odmobject-multiple_axis_joystick.sdf.json
pointer-list = [* sdf-pointer]
optional-comment = (
? $comment: text ; source code comments only, no semantics
)
commonqualities = (
? description: text ; long text (no constraints)
? label: text ; short text (no constraints); default to key
optional-comment
? sdfRef: sdf-pointer
; applies to qualities of properties, of data:
? sdfRequired: pointer-list
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)
arraydefinitionqualities = (
? "minItems" => uint
? "maxItems" => uint
)
paedataqualities = (
; Property represents the state of an instance of an object
? sdfProperty: named<propertyqualities>
; Action invokes an application layer verb associated with an object
? sdfAction: named<actionqualities>
; Event represents an occurrence of event associated with an object
? sdfEvent: named<eventqualities>
; Data represents a piece of information that can be the state of a
; property or a parameter to an action or a signal in an event
? sdfData: named<dataqualities>
)
; for building hierarchy
thingqualities = {
commonqualities
? sdfObject: named<objectqualities>
? sdfThing: named<thingqualities>
paedataqualities
arraydefinitionqualities
EXTENSION-POINT<"thing-ext">
}
; for single objects, or for arrays of objects
objectqualities = {
commonqualities
paedataqualities
arraydefinitionqualities
EXTENSION-POINT<"object-ext">
}
parameter-list = dataqualities
actionqualities = {
commonqualities
? sdfInputData: parameter-list ; sdfRequiredInputData applies here
? sdfOutputData: parameter-list ; sdfRequired applies here
; zero or more named data type definitions that might be used above
? sdfData: named<dataqualities>
EXTENSION-POINT<"action-ext">
}
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eventqualities = {
commonqualities
? sdfOutputData: parameter-list ; sdfRequired applies here
; zero or more named data type definitions that might be used above
? sdfData: named<dataqualities>
EXTENSION-POINT<"event-ext">
}
sdftype-name = text .regexp "[a-z][-a-z0-9]*" ; EXTENSION-POINT
dataqualities = {
commonqualities
jsonschema
? "unit" => text
? nullable: bool
? "sdfType" => "byte-string" / "unix-time"
/ (sdftype-name .feature "sdftype-ext") ; EXTENSION-POINT
? contentFormat: text
EXTENSION-POINT<"data-ext">
}
propertyqualities = {
? observable: bool
? readable: bool
? writable: bool
~dataqualities
}
allowed-types = number / text / bool / null
/ [* number] / [* text] / [* bool]
/ {* text => any}
/ (any .feature "allowed-ext") ; EXTENSION-POINT
compound-type = (
"type" => "object"
? required: [+text]
? properties: named<dataqualities>
)
optional-choice = (
? (("sdfChoice" => named<dataqualities>)
// ("enum" => [+ text])) ; limited to text strings
)
jsonschema = (
? (("type" => "number" / "string" / "boolean" / "integer" / "array")
// compound-type
// (type: text .feature "type-ext") ; EXTENSION-POINT
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)
; if present, all other qualities apply to all choices:
optional-choice
; the next three should validate against type:
? const: allowed-types
? default: allowed-types
; number/integer constraints
? minimum: number
? maximum: number
? exclusiveMinimum: number
? exclusiveMaximum: number
? multipleOf: number
; text string constraints
? minLength: uint
? maxLength: uint
? pattern: text ; regexp
? format: "date-time" / "date" / "time"
/ "uri" / "uri-reference" / "uuid"
/ (text .feature "format-ext") ; EXTENSION-POINT
; array constraints
? minItems: uint
? maxItems: uint
? uniqueItems: bool
? items: jso-items
)
jso-items = {
? sdfRef: sdf-pointer ; import limited to subset allowed here...
? description: text ; long text (no constraints)
optional-comment
; leave commonqualities out for non-complex data types,
; but need the above three.
; no further nesting: no "array"
? ((type: "number" / "string" / "boolean" / "integer")
// compound-type
// (type: text .feature "itemtype-ext") ; EXTENSION-POINT
)
; if present, all other qualities apply to all choices
optional-choice
; jso subset
? minimum: number
? maximum: number
? format: text
? minLength: uint
? maxLength: uint
EXTENSION-POINT<"items-ext">
}
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modified-date-time = text .abnf modified-dt-abnf
modified-dt-abnf = "modified-dt" .det rfc3339z
; RFC 3339 sans time-numoffset, slightly condensed
rfc3339z = '
date-fullyear = 4DIGIT
date-month = 2DIGIT ; 01-12
date-mday = 2DIGIT ; 01-28, 01-29, 01-30, 01-31 based on
; month/year
time-hour = 2DIGIT ; 00-23
time-minute = 2DIGIT ; 00-59
time-second = 2DIGIT ; 00-58, 00-59, 00-60 based on leap sec
; rules
time-secfrac = "." 1*DIGIT
DIGIT = %x30-39 ; 0-9
partial-time = time-hour ":" time-minute ":" time-second
[time-secfrac]
full-date = date-fullyear "-" date-month "-" date-mday
modified-dt = full-date ["T" partial-time "Z"]
'
Appendix B. json-schema.org Rendition of SDF Syntax
This informative appendix describes the syntax of SDF defined in
Appendix A, but using a version of the description techniques
advertised on json-schema.org [JSO7] [JSO7V].
The appendix shows both the validation and the framework syntax.
Since most of the lines are the same between these two files, those
lines are shown only once, with a leading space, in the form of a
unified diff. Lines leading with a - are part of the validation
syntax, and lines leading with a + are part of the framework syntax.
{
- "title": "sdf-validation.cddl -- Generated: 2024-02-29T07:42:35Z",
+ "title": "sdf-framework.cddl -- Generated: 2024-02-29T07:42:52Z",
"$schema": "http://json-schema.org/draft-07/schema#",
"$ref": "#/definitions/sdf-syntax",
"definitions": {
"sdf-syntax": {
"type": "object",
"properties": {
"info": {
"$ref": "#/definitions/sdfinfo"
},
"namespace": {
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"type": "object",
"additionalProperties": {
"type": "string"
}
},
"defaultNamespace": {
"type": "string"
},
"sdfThing": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/thingqualities"
}
},
"sdfObject": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/objectqualities"
}
},
"sdfProperty": {
"$ref": "#/definitions/sdfProperty-"
},
"sdfAction": {
"$ref": "#/definitions/sdfAction-"
},
"sdfEvent": {
"$ref": "#/definitions/sdfEvent-"
},
"sdfData": {
"$ref": "#/definitions/sdfData-sdfChoice-properties-"
}
},
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
"additionalProperties": false
},
"sdfinfo": {
"type": "object",
"properties": {
"title": {
"type": "string"
},
"description": {
"type": "string"
},
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"version": {
"type": "string"
},
"copyright": {
"type": "string"
},
"license": {
"type": "string"
},
"modified": {
"$ref": "#/definitions/modified-date-time"
},
"features": {
- "type": "array",
- "maxItems": 0
+ "type": "array"
},
"$comment": {
"type": "string"
}
},
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
"additionalProperties": false
},
"modified-date-time": {
"type": "string"
},
"thingqualities": {
"type": "object",
"properties": {
"description": {
"type": "string"
},
"label": {
"type": "string"
},
"$comment": {
"type": "string"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"sdfRequired": {
"$ref": "#/definitions/pointer-list"
},
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"sdfObject": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/objectqualities"
}
},
"sdfThing": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/thingqualities"
}
},
"sdfProperty": {
"$ref": "#/definitions/sdfProperty-"
},
"sdfAction": {
"$ref": "#/definitions/sdfAction-"
},
"sdfEvent": {
"$ref": "#/definitions/sdfEvent-"
},
"sdfData": {
"$ref": "#/definitions/sdfData-sdfChoice-properties-"
},
"minItems": {
"$ref": "#/definitions/uint"
},
"maxItems": {
"$ref": "#/definitions/uint"
}
},
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
"additionalProperties": false
},
"sdf-pointer": {
"anyOf": [
{
"$ref": "#/definitions/global"
},
{
"$ref": "#/definitions/same-object"
},
{
"$ref": "#/definitions/true"
}
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]
},
"global": {
"type": "string",
"pattern": "^[^\\n\\r]*[:#][^\\n\\r]*$"
},
"same-object": {
"$ref": "#/definitions/referenceable-name"
},
"referenceable-name": {
"type": "string",
"pattern": "^[^:#]*$"
},
"true": {
"type": "boolean",
"const": true
},
"pointer-list": {
"type": "array",
"items": {
"$ref": "#/definitions/sdf-pointer"
}
},
"objectqualities": {
"type": "object",
"properties": {
"description": {
"type": "string"
},
"label": {
"type": "string"
},
"$comment": {
"type": "string"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"sdfRequired": {
"$ref": "#/definitions/pointer-list"
},
"sdfProperty": {
"$ref": "#/definitions/sdfProperty-"
},
"sdfAction": {
"$ref": "#/definitions/sdfAction-"
},
"sdfEvent": {
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"$ref": "#/definitions/sdfEvent-"
},
"sdfData": {
"$ref": "#/definitions/sdfData-sdfChoice-properties-"
},
"minItems": {
"$ref": "#/definitions/uint"
},
"maxItems": {
"$ref": "#/definitions/uint"
}
},
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
"additionalProperties": false
},
"propertyqualities": {
"anyOf": [
{
"type": "object",
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
"properties": {
"type": {
"$ref": "#/definitions/type-"
},
"sdfChoice": {
"$ref": "#/definitions/sdfData-sdfChoice-properties-"
},
"observable": {
"type": "boolean"
},
"readable": {
"type": "boolean"
},
"writable": {
"type": "boolean"
},
"description": {
"type": "string"
},
"label": {
"type": "string"
},
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"$comment": {
"type": "string"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"sdfRequired": {
"$ref": "#/definitions/pointer-list"
},
"const": {
"$ref": "#/definitions/allowed-types"
},
"default": {
"$ref": "#/definitions/allowed-types"
},
"minimum": {
"type": "number"
},
"maximum": {
"type": "number"
},
"exclusiveMinimum": {
"type": "number"
},
"exclusiveMaximum": {
"type": "number"
},
"multipleOf": {
"type": "number"
},
"minLength": {
"$ref": "#/definitions/uint"
},
"maxLength": {
"$ref": "#/definitions/uint"
},
"pattern": {
"type": "string"
},
"format": {
"$ref": "#/definitions/format-"
},
"minItems": {
"$ref": "#/definitions/uint"
},
"maxItems": {
"$ref": "#/definitions/uint"
},
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"uniqueItems": {
"type": "boolean"
},
"items": {
"$ref": "#/definitions/jso-items"
},
"unit": {
"type": "string"
},
"nullable": {
"type": "boolean"
},
"sdfType": {
"$ref": "#/definitions/sdfType-"
},
"contentFormat": {
"type": "string"
}
},
"additionalProperties": false
},
{
"type": "object",
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
+ "properties": {
+ "type": {
+ "type": "string",
+ "const": "object"
+ },
+ "required": {
+ "type": "array",
+ "items": {
+ "type": "string"
+ },
+ "minItems": 1
+ },
+ "properties": {
+ "$ref": "#/definitions/sdfData-sdfChoice-properties-"
+ },
+ "sdfChoice": {
+ "$ref": "#/definitions/sdfData-sdfChoice-properties-"
+ },
+ "observable": {
+ "type": "boolean"
+ },
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+ "readable": {
+ "type": "boolean"
+ },
+ "writable": {
+ "type": "boolean"
+ },
+ "description": {
+ "type": "string"
+ },
+ "label": {
+ "type": "string"
+ },
+ "$comment": {
+ "type": "string"
+ },
+ "sdfRef": {
+ "$ref": "#/definitions/sdf-pointer"
+ },
+ "sdfRequired": {
+ "$ref": "#/definitions/pointer-list"
+ },
+ "const": {
+ "$ref": "#/definitions/allowed-types"
+ },
+ "default": {
+ "$ref": "#/definitions/allowed-types"
+ },
+ "minimum": {
+ "type": "number"
+ },
+ "maximum": {
+ "type": "number"
+ },
+ "exclusiveMinimum": {
+ "type": "number"
+ },
+ "exclusiveMaximum": {
+ "type": "number"
+ },
+ "multipleOf": {
+ "type": "number"
+ },
+ "minLength": {
+ "$ref": "#/definitions/uint"
+ },
+ "maxLength": {
+ "$ref": "#/definitions/uint"
+ },
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+ "pattern": {
+ "type": "string"
+ },
+ "format": {
+ "$ref": "#/definitions/format-"
+ },
+ "minItems": {
+ "$ref": "#/definitions/uint"
+ },
+ "maxItems": {
+ "$ref": "#/definitions/uint"
+ },
+ "uniqueItems": {
+ "type": "boolean"
+ },
+ "items": {
+ "$ref": "#/definitions/jso-items"
+ },
+ "unit": {
+ "type": "string"
+ },
+ "nullable": {
+ "type": "boolean"
+ },
+ "sdfType": {
+ "$ref": "#/definitions/sdfType-"
+ },
+ "contentFormat": {
+ "type": "string"
+ }
+ },
+ "additionalProperties": false
+ },
+ {
+ "type": "object",
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
+ "properties": {
+ "type": {
+ "type": "string"
+ },
+ "sdfChoice": {
+ "$ref": "#/definitions/sdfData-sdfChoice-properties-"
+ },
+ "observable": {
+ "type": "boolean"
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+ },
+ "readable": {
+ "type": "boolean"
+ },
+ "writable": {
+ "type": "boolean"
+ },
+ "description": {
+ "type": "string"
+ },
+ "label": {
+ "type": "string"
+ },
+ "$comment": {
+ "type": "string"
+ },
+ "sdfRef": {
+ "$ref": "#/definitions/sdf-pointer"
+ },
+ "sdfRequired": {
+ "$ref": "#/definitions/pointer-list"
+ },
+ "const": {
+ "$ref": "#/definitions/allowed-types"
+ },
+ "default": {
+ "$ref": "#/definitions/allowed-types"
+ },
+ "minimum": {
+ "type": "number"
+ },
+ "maximum": {
+ "type": "number"
+ },
+ "exclusiveMinimum": {
+ "type": "number"
+ },
+ "exclusiveMaximum": {
+ "type": "number"
+ },
+ "multipleOf": {
+ "type": "number"
+ },
+ "minLength": {
+ "$ref": "#/definitions/uint"
+ },
+ "maxLength": {
+ "$ref": "#/definitions/uint"
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+ },
+ "pattern": {
+ "type": "string"
+ },
+ "format": {
+ "$ref": "#/definitions/format-"
+ },
+ "minItems": {
+ "$ref": "#/definitions/uint"
+ },
+ "maxItems": {
+ "$ref": "#/definitions/uint"
+ },
+ "uniqueItems": {
+ "type": "boolean"
+ },
+ "items": {
+ "$ref": "#/definitions/jso-items"
+ },
+ "unit": {
+ "type": "string"
+ },
+ "nullable": {
+ "type": "boolean"
+ },
+ "sdfType": {
+ "$ref": "#/definitions/sdfType-"
+ },
+ "contentFormat": {
+ "type": "string"
+ }
+ },
+ "additionalProperties": false
+ },
+ {
+ "type": "object",
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
+ "properties": {
+ "type": {
+ "$ref": "#/definitions/type-"
+ },
+ "enum": {
+ "type": "array",
+ "items": {
+ "type": "string"
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+ },
+ "minItems": 1
+ },
+ "observable": {
+ "type": "boolean"
+ },
+ "readable": {
+ "type": "boolean"
+ },
+ "writable": {
+ "type": "boolean"
+ },
+ "description": {
+ "type": "string"
+ },
+ "label": {
+ "type": "string"
+ },
+ "$comment": {
+ "type": "string"
+ },
+ "sdfRef": {
+ "$ref": "#/definitions/sdf-pointer"
+ },
+ "sdfRequired": {
+ "$ref": "#/definitions/pointer-list"
+ },
+ "const": {
+ "$ref": "#/definitions/allowed-types"
+ },
+ "default": {
+ "$ref": "#/definitions/allowed-types"
+ },
+ "minimum": {
+ "type": "number"
+ },
+ "maximum": {
+ "type": "number"
+ },
+ "exclusiveMinimum": {
+ "type": "number"
+ },
+ "exclusiveMaximum": {
+ "type": "number"
+ },
+ "multipleOf": {
+ "type": "number"
+ },
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+ "minLength": {
+ "$ref": "#/definitions/uint"
+ },
+ "maxLength": {
+ "$ref": "#/definitions/uint"
+ },
+ "pattern": {
+ "type": "string"
+ },
+ "format": {
+ "$ref": "#/definitions/format-"
+ },
+ "minItems": {
+ "$ref": "#/definitions/uint"
+ },
+ "maxItems": {
+ "$ref": "#/definitions/uint"
+ },
+ "uniqueItems": {
+ "type": "boolean"
+ },
+ "items": {
+ "$ref": "#/definitions/jso-items"
+ },
+ "unit": {
+ "type": "string"
+ },
+ "nullable": {
+ "type": "boolean"
+ },
+ "sdfType": {
+ "$ref": "#/definitions/sdfType-"
+ },
+ "contentFormat": {
+ "type": "string"
+ }
+ },
+ "additionalProperties": false
+ },
+ {
+ "type": "object",
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
+ "properties": {
+ "type": {
+ "type": "string",
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+ "const": "object"
+ },
+ "required": {
+ "type": "array",
+ "items": {
+ "type": "string"
+ },
+ "minItems": 1
+ },
+ "properties": {
+ "$ref": "#/definitions/sdfData-sdfChoice-properties-"
+ },
+ "enum": {
+ "type": "array",
+ "items": {
+ "type": "string"
+ },
+ "minItems": 1
+ },
+ "observable": {
+ "type": "boolean"
+ },
+ "readable": {
+ "type": "boolean"
+ },
+ "writable": {
+ "type": "boolean"
+ },
+ "description": {
+ "type": "string"
+ },
+ "label": {
+ "type": "string"
+ },
+ "$comment": {
+ "type": "string"
+ },
+ "sdfRef": {
+ "$ref": "#/definitions/sdf-pointer"
+ },
+ "sdfRequired": {
+ "$ref": "#/definitions/pointer-list"
+ },
+ "const": {
+ "$ref": "#/definitions/allowed-types"
+ },
+ "default": {
+ "$ref": "#/definitions/allowed-types"
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+ },
+ "minimum": {
+ "type": "number"
+ },
+ "maximum": {
+ "type": "number"
+ },
+ "exclusiveMinimum": {
+ "type": "number"
+ },
+ "exclusiveMaximum": {
+ "type": "number"
+ },
+ "multipleOf": {
+ "type": "number"
+ },
+ "minLength": {
+ "$ref": "#/definitions/uint"
+ },
+ "maxLength": {
+ "$ref": "#/definitions/uint"
+ },
+ "pattern": {
+ "type": "string"
+ },
+ "format": {
+ "$ref": "#/definitions/format-"
+ },
+ "minItems": {
+ "$ref": "#/definitions/uint"
+ },
+ "maxItems": {
+ "$ref": "#/definitions/uint"
+ },
+ "uniqueItems": {
+ "type": "boolean"
+ },
+ "items": {
+ "$ref": "#/definitions/jso-items"
+ },
+ "unit": {
+ "type": "string"
+ },
+ "nullable": {
+ "type": "boolean"
+ },
+ "sdfType": {
+ "$ref": "#/definitions/sdfType-"
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+ },
+ "contentFormat": {
+ "type": "string"
+ }
+ },
+ "additionalProperties": false
+ },
+ {
+ "type": "object",
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
"properties": {
"type": {
- "type": "string",
- "const": "object"
+ "type": "string"
},
- "required": {
+ "enum": {
"type": "array",
"items": {
"type": "string"
},
"minItems": 1
},
- "properties": {
- "$ref": "#/definitions/sdfData-sdfChoice-properties-"
- },
- "sdfChoice": {
- "$ref": "#/definitions/sdfData-sdfChoice-properties-"
- },
"observable": {
"type": "boolean"
},
"readable": {
"type": "boolean"
},
"writable": {
"type": "boolean"
},
"description": {
"type": "string"
},
"label": {
"type": "string"
},
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"$comment": {
"type": "string"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"sdfRequired": {
"$ref": "#/definitions/pointer-list"
},
"const": {
"$ref": "#/definitions/allowed-types"
},
"default": {
"$ref": "#/definitions/allowed-types"
},
"minimum": {
"type": "number"
},
"maximum": {
"type": "number"
},
"exclusiveMinimum": {
"type": "number"
},
"exclusiveMaximum": {
"type": "number"
},
"multipleOf": {
"type": "number"
},
"minLength": {
"$ref": "#/definitions/uint"
},
"maxLength": {
"$ref": "#/definitions/uint"
},
"pattern": {
"type": "string"
},
"format": {
"$ref": "#/definitions/format-"
},
"minItems": {
"$ref": "#/definitions/uint"
},
"maxItems": {
"$ref": "#/definitions/uint"
},
Koster, et al. Expires 18 September 2025 [Page 79]
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"uniqueItems": {
"type": "boolean"
},
"items": {
"$ref": "#/definitions/jso-items"
},
"unit": {
"type": "string"
},
"nullable": {
"type": "boolean"
},
"sdfType": {
"$ref": "#/definitions/sdfType-"
},
"contentFormat": {
"type": "string"
}
},
"additionalProperties": false
- },
+ }
+ ]
+ },
+ "dataqualities": {
+ "anyOf": [
{
"type": "object",
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
"properties": {
"type": {
"$ref": "#/definitions/type-"
},
- "enum": {
- "type": "array",
- "items": {
- "type": "string"
- },
- "minItems": 1
- },
- "observable": {
- "type": "boolean"
- },
- "readable": {
- "type": "boolean"
Koster, et al. Expires 18 September 2025 [Page 80]
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- },
- "writable": {
- "type": "boolean"
+ "sdfChoice": {
+ "$ref": "#/definitions/sdfData-sdfChoice-properties-"
},
"description": {
"type": "string"
},
"label": {
"type": "string"
},
"$comment": {
"type": "string"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"sdfRequired": {
"$ref": "#/definitions/pointer-list"
},
"const": {
"$ref": "#/definitions/allowed-types"
},
"default": {
"$ref": "#/definitions/allowed-types"
},
"minimum": {
"type": "number"
},
"maximum": {
"type": "number"
},
"exclusiveMinimum": {
"type": "number"
},
"exclusiveMaximum": {
"type": "number"
},
"multipleOf": {
"type": "number"
},
"minLength": {
"$ref": "#/definitions/uint"
},
"maxLength": {
"$ref": "#/definitions/uint"
},
Koster, et al. Expires 18 September 2025 [Page 81]
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"pattern": {
"type": "string"
},
"format": {
"$ref": "#/definitions/format-"
},
"minItems": {
"$ref": "#/definitions/uint"
},
"maxItems": {
"$ref": "#/definitions/uint"
},
"uniqueItems": {
"type": "boolean"
},
"items": {
"$ref": "#/definitions/jso-items"
},
"unit": {
"type": "string"
},
"nullable": {
"type": "boolean"
},
"sdfType": {
"$ref": "#/definitions/sdfType-"
},
"contentFormat": {
"type": "string"
}
},
"additionalProperties": false
},
{
"type": "object",
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
"properties": {
"type": {
"type": "string",
"const": "object"
},
"required": {
"type": "array",
"items": {
"type": "string"
Koster, et al. Expires 18 September 2025 [Page 82]
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},
"minItems": 1
},
"properties": {
"$ref": "#/definitions/sdfData-sdfChoice-properties-"
},
- "enum": {
- "type": "array",
- "items": {
- "type": "string"
- },
- "minItems": 1
- },
- "observable": {
- "type": "boolean"
- },
- "readable": {
- "type": "boolean"
- },
- "writable": {
- "type": "boolean"
+ "sdfChoice": {
+ "$ref": "#/definitions/sdfData-sdfChoice-properties-"
},
"description": {
"type": "string"
},
"label": {
"type": "string"
},
"$comment": {
"type": "string"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"sdfRequired": {
"$ref": "#/definitions/pointer-list"
},
"const": {
"$ref": "#/definitions/allowed-types"
},
"default": {
"$ref": "#/definitions/allowed-types"
},
"minimum": {
"type": "number"
},
Koster, et al. Expires 18 September 2025 [Page 83]
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"maximum": {
"type": "number"
},
"exclusiveMinimum": {
"type": "number"
},
"exclusiveMaximum": {
"type": "number"
},
"multipleOf": {
"type": "number"
},
"minLength": {
"$ref": "#/definitions/uint"
},
"maxLength": {
"$ref": "#/definitions/uint"
},
"pattern": {
"type": "string"
},
"format": {
"$ref": "#/definitions/format-"
},
"minItems": {
"$ref": "#/definitions/uint"
},
"maxItems": {
"$ref": "#/definitions/uint"
},
"uniqueItems": {
"type": "boolean"
},
"items": {
"$ref": "#/definitions/jso-items"
},
"unit": {
"type": "string"
},
"nullable": {
"type": "boolean"
},
"sdfType": {
"$ref": "#/definitions/sdfType-"
},
"contentFormat": {
"type": "string"
}
Koster, et al. Expires 18 September 2025 [Page 84]
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},
"additionalProperties": false
- }
- ]
- },
- "dataqualities": {
- "anyOf": [
+ },
{
"type": "object",
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
"properties": {
"type": {
- "$ref": "#/definitions/type-"
+ "type": "string"
},
"sdfChoice": {
"$ref": "#/definitions/sdfData-sdfChoice-properties-"
},
"description": {
"type": "string"
},
"label": {
"type": "string"
},
"$comment": {
"type": "string"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"sdfRequired": {
"$ref": "#/definitions/pointer-list"
},
"const": {
"$ref": "#/definitions/allowed-types"
},
"default": {
"$ref": "#/definitions/allowed-types"
},
"minimum": {
"type": "number"
},
"maximum": {
"type": "number"
Koster, et al. Expires 18 September 2025 [Page 85]
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},
"exclusiveMinimum": {
"type": "number"
},
"exclusiveMaximum": {
"type": "number"
},
"multipleOf": {
"type": "number"
},
"minLength": {
"$ref": "#/definitions/uint"
},
"maxLength": {
"$ref": "#/definitions/uint"
},
"pattern": {
"type": "string"
},
"format": {
"$ref": "#/definitions/format-"
},
"minItems": {
"$ref": "#/definitions/uint"
},
"maxItems": {
"$ref": "#/definitions/uint"
},
"uniqueItems": {
"type": "boolean"
},
"items": {
"$ref": "#/definitions/jso-items"
},
"unit": {
"type": "string"
},
"nullable": {
"type": "boolean"
},
"sdfType": {
"$ref": "#/definitions/sdfType-"
},
"contentFormat": {
"type": "string"
}
},
"additionalProperties": false
Koster, et al. Expires 18 September 2025 [Page 86]
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},
{
"type": "object",
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
"properties": {
"type": {
- "type": "string",
- "const": "object"
+ "$ref": "#/definitions/type-"
},
- "required": {
+ "enum": {
"type": "array",
"items": {
"type": "string"
},
"minItems": 1
},
- "properties": {
- "$ref": "#/definitions/sdfData-sdfChoice-properties-"
- },
- "sdfChoice": {
- "$ref": "#/definitions/sdfData-sdfChoice-properties-"
- },
"description": {
"type": "string"
},
"label": {
"type": "string"
},
"$comment": {
"type": "string"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"sdfRequired": {
"$ref": "#/definitions/pointer-list"
},
"const": {
"$ref": "#/definitions/allowed-types"
},
"default": {
"$ref": "#/definitions/allowed-types"
},
Koster, et al. Expires 18 September 2025 [Page 87]
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"minimum": {
"type": "number"
},
"maximum": {
"type": "number"
},
"exclusiveMinimum": {
"type": "number"
},
"exclusiveMaximum": {
"type": "number"
},
"multipleOf": {
"type": "number"
},
"minLength": {
"$ref": "#/definitions/uint"
},
"maxLength": {
"$ref": "#/definitions/uint"
},
"pattern": {
"type": "string"
},
"format": {
"$ref": "#/definitions/format-"
},
"minItems": {
"$ref": "#/definitions/uint"
},
"maxItems": {
"$ref": "#/definitions/uint"
},
"uniqueItems": {
"type": "boolean"
},
"items": {
"$ref": "#/definitions/jso-items"
},
"unit": {
"type": "string"
},
"nullable": {
"type": "boolean"
},
"sdfType": {
"$ref": "#/definitions/sdfType-"
},
Koster, et al. Expires 18 September 2025 [Page 88]
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"contentFormat": {
"type": "string"
}
},
"additionalProperties": false
},
{
"type": "object",
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
"properties": {
"type": {
- "$ref": "#/definitions/type-"
+ "type": "string",
+ "const": "object"
+ },
+ "required": {
+ "type": "array",
+ "items": {
+ "type": "string"
+ },
+ "minItems": 1
+ },
+ "properties": {
+ "$ref": "#/definitions/sdfData-sdfChoice-properties-"
},
"enum": {
"type": "array",
"items": {
"type": "string"
},
"minItems": 1
},
"description": {
"type": "string"
},
"label": {
"type": "string"
},
"$comment": {
"type": "string"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"sdfRequired": {
Koster, et al. Expires 18 September 2025 [Page 89]
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"$ref": "#/definitions/pointer-list"
},
"const": {
"$ref": "#/definitions/allowed-types"
},
"default": {
"$ref": "#/definitions/allowed-types"
},
"minimum": {
"type": "number"
},
"maximum": {
"type": "number"
},
"exclusiveMinimum": {
"type": "number"
},
"exclusiveMaximum": {
"type": "number"
},
"multipleOf": {
"type": "number"
},
"minLength": {
"$ref": "#/definitions/uint"
},
"maxLength": {
"$ref": "#/definitions/uint"
},
"pattern": {
"type": "string"
},
"format": {
"$ref": "#/definitions/format-"
},
"minItems": {
"$ref": "#/definitions/uint"
},
"maxItems": {
"$ref": "#/definitions/uint"
},
"uniqueItems": {
"type": "boolean"
},
"items": {
"$ref": "#/definitions/jso-items"
},
"unit": {
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"type": "string"
},
"nullable": {
"type": "boolean"
},
"sdfType": {
"$ref": "#/definitions/sdfType-"
},
"contentFormat": {
"type": "string"
}
},
"additionalProperties": false
},
{
"type": "object",
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
"properties": {
"type": {
- "type": "string",
- "const": "object"
- },
- "required": {
- "type": "array",
- "items": {
- "type": "string"
- },
- "minItems": 1
- },
- "properties": {
- "$ref": "#/definitions/sdfData-sdfChoice-properties-"
+ "type": "string"
},
"enum": {
"type": "array",
"items": {
"type": "string"
},
"minItems": 1
},
"description": {
"type": "string"
},
"label": {
"type": "string"
Koster, et al. Expires 18 September 2025 [Page 91]
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},
"$comment": {
"type": "string"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"sdfRequired": {
"$ref": "#/definitions/pointer-list"
},
"const": {
"$ref": "#/definitions/allowed-types"
},
"default": {
"$ref": "#/definitions/allowed-types"
},
"minimum": {
"type": "number"
},
"maximum": {
"type": "number"
},
"exclusiveMinimum": {
"type": "number"
},
"exclusiveMaximum": {
"type": "number"
},
"multipleOf": {
"type": "number"
},
"minLength": {
"$ref": "#/definitions/uint"
},
"maxLength": {
"$ref": "#/definitions/uint"
},
"pattern": {
"type": "string"
},
"format": {
"$ref": "#/definitions/format-"
},
"minItems": {
"$ref": "#/definitions/uint"
},
"maxItems": {
"$ref": "#/definitions/uint"
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},
"uniqueItems": {
"type": "boolean"
},
"items": {
"$ref": "#/definitions/jso-items"
},
"unit": {
"type": "string"
},
"nullable": {
"type": "boolean"
},
"sdfType": {
"$ref": "#/definitions/sdfType-"
},
"contentFormat": {
"type": "string"
}
},
"additionalProperties": false
}
]
},
"allowed-types": {
"anyOf": [
{
"type": "number"
},
{
"type": "string"
},
{
"type": "boolean"
},
{
"type": "null"
},
{
"type": "array",
"items": {
"type": "number"
}
},
{
"type": "array",
"items": {
"type": "string"
Koster, et al. Expires 18 September 2025 [Page 93]
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}
},
{
"type": "array",
"items": {
"type": "boolean"
}
},
{
"type": "object",
"additionalProperties": {
}
+ },
+ {
}
]
},
"uint": {
"type": "integer",
"minimum": 0
},
"jso-items": {
"anyOf": [
{
"type": "object",
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
"properties": {
"type": {
"type": "string",
"enum": [
"number",
"string",
"boolean",
"integer"
]
},
"sdfChoice": {
"$ref": "#/definitions/sdfData-sdfChoice-properties-"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"description": {
"type": "string"
},
Koster, et al. Expires 18 September 2025 [Page 94]
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"$comment": {
"type": "string"
},
"minimum": {
"type": "number"
},
"maximum": {
"type": "number"
},
"format": {
"type": "string"
},
"minLength": {
"$ref": "#/definitions/uint"
},
"maxLength": {
"$ref": "#/definitions/uint"
}
},
"additionalProperties": false
},
{
"type": "object",
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
"properties": {
"type": {
"type": "string",
"const": "object"
},
"required": {
"type": "array",
"items": {
"type": "string"
},
"minItems": 1
},
"properties": {
"$ref": "#/definitions/sdfData-sdfChoice-properties-"
},
"sdfChoice": {
"$ref": "#/definitions/sdfData-sdfChoice-properties-"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
Koster, et al. Expires 18 September 2025 [Page 95]
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"description": {
"type": "string"
},
"$comment": {
"type": "string"
},
"minimum": {
"type": "number"
},
"maximum": {
"type": "number"
},
"format": {
"type": "string"
},
"minLength": {
"$ref": "#/definitions/uint"
},
"maxLength": {
"$ref": "#/definitions/uint"
}
},
"additionalProperties": false
},
{
"type": "object",
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
+ "properties": {
+ "type": {
+ "type": "string"
+ },
+ "sdfChoice": {
+ "$ref": "#/definitions/sdfData-sdfChoice-properties-"
+ },
+ "sdfRef": {
+ "$ref": "#/definitions/sdf-pointer"
+ },
+ "description": {
+ "type": "string"
+ },
+ "$comment": {
+ "type": "string"
+ },
+ "minimum": {
+ "type": "number"
Koster, et al. Expires 18 September 2025 [Page 96]
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+ },
+ "maximum": {
+ "type": "number"
+ },
+ "format": {
+ "type": "string"
+ },
+ "minLength": {
+ "$ref": "#/definitions/uint"
+ },
+ "maxLength": {
+ "$ref": "#/definitions/uint"
+ }
+ },
+ "additionalProperties": false
+ },
+ {
+ "type": "object",
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
"properties": {
"type": {
"type": "string",
"enum": [
"number",
"string",
"boolean",
"integer"
]
},
"enum": {
"type": "array",
"items": {
"type": "string"
},
"minItems": 1
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"description": {
"type": "string"
},
"$comment": {
"type": "string"
},
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"minimum": {
"type": "number"
},
"maximum": {
"type": "number"
},
"format": {
"type": "string"
},
"minLength": {
"$ref": "#/definitions/uint"
},
"maxLength": {
"$ref": "#/definitions/uint"
}
},
"additionalProperties": false
},
{
"type": "object",
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
"properties": {
"type": {
"type": "string",
"const": "object"
},
"required": {
"type": "array",
"items": {
"type": "string"
},
"minItems": 1
},
"properties": {
"$ref": "#/definitions/sdfData-sdfChoice-properties-"
},
"enum": {
"type": "array",
"items": {
"type": "string"
},
"minItems": 1
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
Koster, et al. Expires 18 September 2025 [Page 98]
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},
"description": {
"type": "string"
},
"$comment": {
"type": "string"
},
"minimum": {
"type": "number"
},
"maximum": {
"type": "number"
},
"format": {
"type": "string"
},
"minLength": {
"$ref": "#/definitions/uint"
},
"maxLength": {
"$ref": "#/definitions/uint"
}
},
"additionalProperties": false
+ },
+ {
+ "type": "object",
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
+ "properties": {
+ "type": {
+ "type": "string"
+ },
+ "enum": {
+ "type": "array",
+ "items": {
+ "type": "string"
+ },
+ "minItems": 1
+ },
+ "sdfRef": {
+ "$ref": "#/definitions/sdf-pointer"
+ },
+ "description": {
+ "type": "string"
+ },
Koster, et al. Expires 18 September 2025 [Page 99]
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+ "$comment": {
+ "type": "string"
+ },
+ "minimum": {
+ "type": "number"
+ },
+ "maximum": {
+ "type": "number"
+ },
+ "format": {
+ "type": "string"
+ },
+ "minLength": {
+ "$ref": "#/definitions/uint"
+ },
+ "maxLength": {
+ "$ref": "#/definitions/uint"
+ }
+ },
+ "additionalProperties": false
}
]
},
+ "sdftype-name": {
+ "type": "string",
+ "pattern": "^[a-z][\\-a-z0-9]*$"
+ },
"actionqualities": {
"type": "object",
"properties": {
"description": {
"type": "string"
},
"label": {
"type": "string"
},
"$comment": {
"type": "string"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"sdfRequired": {
"$ref": "#/definitions/pointer-list"
},
"sdfInputData": {
"$ref": "#/definitions/parameter-list"
},
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"sdfOutputData": {
"$ref": "#/definitions/parameter-list"
},
"sdfData": {
"$ref": "#/definitions/sdfData-sdfChoice-properties-"
}
},
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
"additionalProperties": false
},
"parameter-list": {
"$ref": "#/definitions/dataqualities"
},
"eventqualities": {
"type": "object",
"properties": {
"description": {
"type": "string"
},
"label": {
"type": "string"
},
"$comment": {
"type": "string"
},
"sdfRef": {
"$ref": "#/definitions/sdf-pointer"
},
"sdfRequired": {
"$ref": "#/definitions/pointer-list"
},
"sdfOutputData": {
"$ref": "#/definitions/parameter-list"
},
"sdfData": {
"$ref": "#/definitions/sdfData-sdfChoice-properties-"
}
},
+ "patternProperties": {
+ "^(?:[a-z][a-z0-9]*:)?[a-z$][A-Za-z$0-9]*$": {
+ }
+ },
"additionalProperties": false
},
"format-": {
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- "type": "string",
- "enum": [
- "date-time",
- "date",
- "time",
- "uri",
- "uri-reference",
- "uuid"
+ "anyOf": [
+ {
+ "type": "string",
+ "const": "date-time"
+ },
+ {
+ "type": "string",
+ "const": "date"
+ },
+ {
+ "type": "string",
+ "const": "time"
+ },
+ {
+ "type": "string",
+ "const": "uri"
+ },
+ {
+ "type": "string",
+ "const": "uri-reference"
+ },
+ {
+ "type": "string",
+ "const": "uuid"
+ },
+ {
+ "type": "string"
+ }
+ ]
+ },
+ "sdfType-": {
+ "anyOf": [
+ {
+ "type": "string",
+ "const": "byte-string"
+ },
+ {
+ "type": "string",
+ "const": "unix-time"
+ },
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+ {
+ "$ref": "#/definitions/sdftype-name"
+ }
]
},
"sdfData-sdfChoice-properties-": {
"type": "object",
"additionalProperties": {
"$ref": "#/definitions/dataqualities"
}
},
"type-": {
"type": "string",
"enum": [
"number",
"string",
"boolean",
"integer",
"array"
]
},
- "sdfAction-": {
+ "sdfEvent-": {
"type": "object",
"additionalProperties": {
- "$ref": "#/definitions/actionqualities"
+ "$ref": "#/definitions/eventqualities"
}
},
- "sdfProperty-": {
+ "sdfAction-": {
"type": "object",
"additionalProperties": {
- "$ref": "#/definitions/propertyqualities"
+ "$ref": "#/definitions/actionqualities"
}
},
- "sdfEvent-": {
+ "sdfProperty-": {
"type": "object",
"additionalProperties": {
- "$ref": "#/definitions/eventqualities"
+ "$ref": "#/definitions/propertyqualities"
}
- },
- "sdfType-": {
- "type": "string",
- "enum": [
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- "byte-string",
- "unix-time"
- ]
}
}
}
Appendix C. Data Qualities inspired by json-schema.org
This appendix is normative.
Data qualities define data used in SDF affordances at an information
model level. A popular way to describe JSON data at a data model
level is proposed by a number of drafts on json-schema.org (which
collectively are abbreviated JSO here); for reference to a popular
version this appendix points to [JSO7] and [JSO7V]. As the
vocabulary used by JSO is familiar to many JSON modelers, the present
specification borrows some of the terms and ports their semantics to
the information model level needed for SDF.
The main data quality imported is the "type". In SDF, this can take
one of six (text string) values, which are discussed in the following
subsections (note that the JSO type "null" is not supported as a
value of this data quality in SDF).
The additional quality "const" restricts the data to one specific
value (given as the value of the const quality).
Similarly, the additional quality "default" provides data that can be
used in the absence of the data (given as the value of the const
quality); this is mainly documentary and not very well-defined for
SDF as no process is defined that would add default values to an
instance of some interaction data.
Other qualities that are inspired by JSO are "$comment" and
"description", both of which are also available in the information
block.
C.1. type "number", type "integer"
The types "number" and "integer" are associated with floating point
and integer numbers, as they are available in JSON. A type value of
integer means that only integer values of JSON numbers can be used
(note that 10.0 is an integer value, even if it is in a notation that
would also allow non-zero decimal fractions).
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The additional data qualities "minimum", "maximum",
"exclusiveMinimum", "exclusiveMaximum" provide number values that
serve as inclusive/exclusive lower/upper bounds for the number.
(Note that the Boolean form of "exclusiveMinimum"/"exclusiveMaximum"
found in earlier JSO drafts [JSO4V] is not used.)
The data quality "multipleOf" gives a positive number that constrains
the data value to be an integer multiple of the number given. (Type
"integer" can also be expressed as a "multipleOf" quality of value 1,
unless another "multipleOf" quality is present.)
C.2. type "string"
The type "string" is associated with Unicode text string values as
they can be represented in JSON.
The length (as measured in characters, specifically Unicode scalar
values) can be constrained by the additional data qualities
"minLength" and "maxLength", which are inclusive bounds.
(More specifically, Unicode text strings as defined in this
specification are sequences of Unicode scalar values, the number of
which is taken as the length of such a text string.
The data quality "pattern" takes a string value that is interpreted
as an [ECMA-262] regular expression in Unicode mode that constrains
the string (note that these are not anchored by default, so unless ^
and $ anchors are employed, ECMA-262 regular expressions match any
string that _contains_ a match). The JSO proposals acknowledge that
regular expression support is rather diverse in various platforms, so
the suggestion is to limit them to:
* characters;
* character classes in square brackets, including ranges; their
complements;
* simple quantifiers *, +, ?, and range quantifiers {n}, {n,m}, and
{n,};
* grouping parentheses;
* the choice operator |;
* and anchors (beginning-of-input ^ and end-of-input $).
Note that this subset is somewhat similar to the subset introduced by
I-Regexps [RFC9485], which however are anchored regular expressions,
and which include certain backslash escapes for characters and
character classes.
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The additional data quality "format" can take one of the following
values. Note that, at an information model level, the presence of
this data quality changes the type from being a simple text string to
the abstract meaning of the format given (i.e., the format "date-
time" is less about the specific syntax employed in [RFC3339] than
about the usage as an absolute point in civil time).
* "date-time", "date", "time": An [RFC3339] date-time, full-date, or
full-time, respectively.
* "uri", "uri-reference": An [STD66] URI or URI Reference,
respectively.
* "uuid": An [RFC9562] UUID.
C.3. type "boolean"
The type "boolean" can take the values "true" or "false".
C.4. type "array"
The type "array" is associated with arrays as they are available in
JSON.
The additional quality "items" gives the type that each of the
elements of the array must match.
The number of elements in the array can be constrained by the
additional data qualities "minItems" and "maxItems", which are
inclusive bounds.
The additional data quality "uniqueItems" gives a Boolean value that,
if true, requires the elements to be all different.
C.5. type "object"
The type "object" is associated with maps, from strings to values, as
they are available in JSON.
The additional quality "properties" is a map the entries of which
describe entries in the specified JSON map: The key gives an
allowable map key for the specified JSON map, and the value is a map
with a named set of data qualities giving the type for the
corresponding value in the specified JSON map.
All entries specified this way are optional, unless they are listed
in the value of the additional quality "required", which is an array
of string values that give the key names of required entries.
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Note that the term "properties" as an additional quality for defining
map entries is unrelated to sdfProperty.
For example, to include information about the type of the event in
the "overTemperatureEvent" of Figure 4, the sdfOutputData there could
be defined as follows:
"sdfOutputData": {
"type": "object",
"properties": {
"alarmType": {
"sdfRef": "cap:#/sdfData/alarmTypes/quantityAlarms",
"const": "OverTemperatureAlarm"
},
"temperature": {
"sdfRef": "#/sdfObject/temperatureWithAlarm/sdfData/temperatureData"
}
}
}
Figure 6: Using object type with sdfOutputData
C.6. Implementation notes
JSO-based keywords are also used in the specification techniques of a
number of ecosystems, but some adjustments may be required.
For instance, [OCF] is based on Swagger 2.0 which appears to be based
on "draft-4" [JSO4][JSO4V] (also called draft-5, but semantically
intended to be equivalent to draft-4). The "exclusiveMinimum" and
"exclusiveMaximum" keywords use the Boolean form there, so on import
to SDF their values have to be replaced by the values of the
respective "minimum"/"maximum" keyword, which are themselves then
removed; the reverse transformation applies on export.
Appendix D. Composition Examples
This informative appendix contains two examples illustrating
different composition approaches using the sdfThing quality.
D.1. Outlet Strip Example
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{
"sdfThing": {
"outlet-strip": {
"label": "Outlet strip",
"description": "Contains a number of Sockets",
"sdfObject": {
"socket": {
"description": "An array of sockets in the outlet strip",
"minItems": 2,
"maxItems": 10
}
}
}
}
}
Figure 7: Outlet Strip Example
D.2. Refrigerator-Freezer Example
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{
"sdfThing": {
"refrigerator-freezer": {
"description": "A refrigerator combined with a freezer",
"sdfProperty": {
"status": {
"type": "boolean",
"description":
"Indicates if the refrigerator-freezer is powered"
}
},
"sdfObject": {
"refrigerator": {
"description": "A refrigerator compartment",
"sdfProperty": {
"temperature": {
"sdfRef": "#/sdfProproperty/temperature",
"maximum": 8
}
}
},
"freezer": {
"label": "A freezer compartment",
"sdfProperty": {
"temperature": {
"sdfRef": "#/sdfProproperty/temperature",
"maximum": -6
}
}
}
}
}
},
"sdfProperty": {
"temperature": {
"description": "The temperature for this compartment",
"type": "number",
"unit": "Cel"
}
}
}
Figure 8: Refrigerator-Freezer Example
Appendix E. Some Changes From Earlier Drafts
This appendix is informative.
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The present document provides the SDF base definition. Previous
revisions of SDF have been in use for several years, and both
significant collections of older SDF models and older SDF conversion
tools are available today. This appendix provides a brief checklist
that can aid in upgrading these to the standard.
* The quality unit was previously called units.
* sdfType was developed out of a concept previously called subtype.
* sdfChoice is the preferred way to represent JSO enum (only a
limited form of which is retained), and also the way to represent
JSO anyOf.
* the length of text strings (as used with minLength/maxLength
constraints) was previously defined in bytes. It now is defined
as the number of characters (Unicode scalar values, to be exact);
a length in bytes is not meaningful unless bound to a specific
encoding, which might differ from UTF-8 in some ecosystem mappings
and protocol bindings.
List of Figures
Figure 1: A simple example of an SDF document
Figure 2: Main classes used in SDF models
Figure 3: Example sdfObject definition
Figure 4: Using sdfRequired
Figure 5: Using an Override to Further Restrict the Set of Data
Values
Figure 6: Using object type with sdfOutputData
Figure 7: Outlet Strip Example
Figure 8: Refrigerator-Freezer Example
List of Tables
Table 1: Qualities of the Information Block
Table 2: Namespaces Block
Table 3: Common Qualities
Table 4: SDF-defined Qualities of sdfData and sdfProperty
Table 5: Values Defined in Base SDF for the sdfType Quality
Table 6: Qualities of sdfObject
Table 7: Qualities of sdfProperty
Table 8: Qualities of sdfAction
Table 9: Qualities of sdfEvent
Table 10: Qualities of sdfThing
Table 11: Media Type Registration for SDF
Table 12: SDF Content-format Registration
Table 13: Initial Content of Quality Names Registry
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Acknowledgements
This specification is based on work by the One Data Model group.
Contributors
Jan Romann
Hochschule Emden/Leer
Germany
Email: jan.romann@hs-emden-leer.de
Wouter van der Beek
Cascoda Ltd.
Threefield House
Threefield Lane
Southampton
United Kingdom
Email: w.vanderbeek@cascoda.com
Authors' Addresses
Michael Koster (editor)
KTC Control AB
29415 Alderpoint Road
Blocksburg, CA, 95514
United States of America
Phone: +1-707-502-5136
Email: michaeljohnkoster@gmail.com
Carsten Bormann (editor)
Universität Bremen TZI
Postfach 330440
D-28359 Bremen
Germany
Phone: +49-421-218-63921
Email: cabo@tzi.org
Ari Keränen
Ericsson
FI-02420 Jorvas
Finland
Email: ari.keranen@ericsson.com
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