JSON Schema extensions

[Seth]

I wrote up a set of rules for JSON Schema extension which follow from
the JSON Schema specification and a validator to validate those
rules. I've called it JSON Schema Extension Validation or JSEV and
posted it to a Google project page (http://code.google.com/p/jsev/).

I'd appreciate comments, either positive or negative.

Also, I've found that a new schema property (or restriction as I call
them) additionalItems should be added for a couple of reasons.

First, unrelated to JSEV is the fact that if one wanted to create a
union type of object and array there would be no way to specify
different types for the additional properties of the object and the
additional items of the array. I can't say why one would want to
create a union type of object and array but it's possible.

Second, and this one is related to JSEV, when checking whether these
restrictions (additionalProperties, additionalItems) are valid or not
there are different requirements so again it makes sense that there
should be two unique restrictions rather than the one
additionalProperties restriction.