
Config::Model - Framework for semantic validation of config data

The Config::Model provides a framework to help in validating the
semantic content of configuration data.

How does this work ?
--------------------

Using this project, a typical configuration validation tool will be
made of 3 parts :

   1. The user interface
   2. The validation engine which is in charge of validating all the
      configuration information provided by the user.
   3. The storage facility that store the configuration information

The important part is the validation engine. 

Don't we already have some configuration validation tools ?
-----------------------------------------------------------

You're probably thinking of tools like webmin. Yes, these tools exist
and work fine, but they have their set of drawbacks.

Usually, the validation of configuration data is done with a script
which performs semantic validation and often ends up being quite
complex (e.g. 2500 lines for Debian's xserver-xorg.config script which
handles xorg.conf file). 

In most cases, the configuration model is expressed in instructions
(whatever programming language is used) and interspersed with a lot of
processing to handle the actual configuration data.

What's the advantage of this project ?
--------------------------------------

The Config::Model projects provide a way to get a validation engine
where the configuration model is completely separated from the actual
processing instruction.

The configuration model is expressed in a declarative form (i.e. a
Perl data structure) which is always easier to maintain than a lot of
code.

The declaration specifies:
- the structure of the configuration data (which can be queried by
  generic user interfaces)
- the properties of each element (boundaries, check, integer or
  string, enum like type ...)
- the default values of parameters (if any)
- mandatory parameters
- the targeted audience (intermediate, advance, master)
- on-line help (for ach parameter or value of parameter)
- the level of expertise of each parameter (to hide expert parameters
  from newbie eyes)

So, in the end:
- maintenance and evolution of the configuration content is easier
- user will see a *common* interface for *all* programs using this
  project.
- user will not see advanced parameters
- upgrade of configuration data is easier and sanity check is
  performed
- audit of configuration is possible to check what was modified by the
  user compated to default values

What about the user interface ?
-------------------------------

Config::Model will also come with a Curses::UI interface that queries
the user's model and generate the relevant user screens.

Why an old-fashioned Curses interface ?
To be able to configure your system even if X is not running.

What about data storage ?
-------------------------

Since the syntax of configuration files vary wildly form one program
to another, most people who want to use this framework will have to
provide a dedicated parser/writer. 

Nevertheless, this project can also provide a writer/parser for most
common format: like ini style file, or provide an interface to the
Elektra or debconf projects. This point is open for discussion.

It is entirely possible for a single configuration model to use
several parsers and writers so one model will ensure the consistency
of several configuration files together.

Where does this come from ?
---------------------------

So far this set of modules have succesfully been used by HP on
proprietary products. I've recently got the authorisation to make it
an open source project.

Do you have an example of a model ?
-----------------------------------

The "example" directory contains a configuration model example for the
/etc/fstab file. This example includes a small program that use this
model to show some ways to extract configuration informations.

Where can I get more doc ?
--------------------------

On sourceforge:
  http://sourceforge.net/projects/config-model

What's the licence ?
------------------

    Copyright (c) 2005 Dominique Dumont.

    This file is part of Config-Model.

    Config-Model is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser Public License as
    published by the Free Software Foundation; either version 2.1 of
    the License, or (at your option) any later version.

    Config-Model is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser Public License for more details.

    You should have received a copy of the GNU Lesser Public License
    along with Config-Model; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
    02110-1301 USA

---------------------------------------------------------------------
INSTALLATION

   	 gunzip -c <dist_file>.tar.gz | tar xvf -
   	 cd <dist_directory>
   	 perl Makefile.PL
   	 make test          

If you want to install this software without packaging, type also:

   	 make install
