Versioning Schema URIs

[Gary Court]

I would like to propose that, going forward on JSON Schema
specification revisions, we start versioning the official JSON Schema/
Hyper-Schema URIs. What I mean by this is that for each revision of
the offical JSON Schema specification, we create new official JSON
Schema/Hyper-Schema URIs for that version.

For example; For the next revision (3) of the JSON Schema
specification, the URIs of the JSON Schema would be:
http://json-schema.org/draft-03/schema
http://json-schema.org/draft-03/hyper-schema

The reason I propose this is that it would allow a JSON Schema
validator to validate a JSON document based on the rules of the
version the schema is written to.

For example; take the following schema:

{
"$schema" : "http://json-schema.org/draft-02/hyper-schema",
"properties" : {
"a" : {}
}
}

A validator can examine the "describedby" link "$schema" and
understand that this schema (and it's subschemas) are written assuming
revision 2 rules, and that the property "a" is required (not optional,
unlike revision 3 rules). Because any schema can have this link, this
allows for embedding/referencing other schemas that validate using
newer (or older) schema rules.

This would immensely help in providing backwards compatability with
schemas written using older revision rules.