Compound documents require “full linkage”, meaning that every included resource MUST be identified by at least one resource identifier object in the same document. These resource identifier objects could either be primary data or represent resource linkage contained within primary or included resources.
Native English speaker needed (@tobscure?)
Which is the best?
$a->identifies($b): bool
$a->doesIdentify($b): bool
$b->isIdentifiedBy($a): bool
$a->isIdentityOf($b): bool