                               Set::Relation
---------------------------------------------------------------------------

Following is a summary of things that still need doing.

* Add or confirm we have input checks regarding any attempts to insert a
Set::Relation object into itself as an attribute value.  An exception
specific to this bad recursion should be thrown, rather than some other
problem happening later ... such as the insert eventually dying on an
infinite _ident_str/etc recursion.

* Make these operators N-ary: union, exclusion, intersection, join,
product; if any were missed, then those too; rename arg to 'others'.

* Add relational operators for wrap/unwrap, group/ungroup, summarize,
transitive closure, reduction, rank and quota, substitution, outer joins,
other misc missing.

* Add code examples, tutorial, cookbook, FAQ, etc.

* Make the test suite actually run the code, not just compile it; maybe
start off with running same code examples in documentation, tutorial, etc.

* Consider adding public operators such as for comparing headings eg for
disjointness etc, mirroring some set operators, perhaps to help users
implement more operators?

* Consider adding disjoint insertion, union operators (same as normal but
fails on a duplicate).

* Consider adding support for explicit keys / unique key constraints on
Set::Relation objects.

* Consider adding more mutator methods.

* Improve performance.

* Port this to Perl 6 again; meanwhile, a much older initial version
pre-dating this Perl 5 rewrite already exists FYI.

* Whatever else needs doing, such as, fixing bugs.
