Codify the meaning of "undefined" and "implementation-defined"

[handrews]

We already use these terms a bit in the spec, but with PRs like these:

• Limit interoperable parsing expectations (avoid type conflicts) #3732
• Clarify interoperable parsing expectations (3.0.4 port of #3732) #3772
• Clarify how Schema Objects require full-document parsing (3.1.1) #3758

we are relying more on such descriptions to define areas of interoperability and expected compliance. A new subsection under the Definitions section seems like the best approach.

[handrews]

Thanks to @kevinswiber for suggesting this - Kevin (and anyone) please feel free to add suggestions or closely related terms that we should consider. I'll make a PR for this soon.

[miqui]

Thanks to @kevinswiber for suggesting this - Kevin (and anyone) please feel free to add suggestions or closely related terms that we should consider. I'll make a PR for this soon.

Agreed. Looking forward to the PR

[handrews]

All PRs merged, closing!