It doesn’t make much sense to have an <org>, a <person>, or a <place> that does not have an xml:id= attribute. One can imagine a case where this is done (and thus the xml:id= attribute is not required), but all our examples should show an xml:id=, since this is the intended use case, and by far the most common.
Agreed
Done in revision r12982. In a few examples it made sense not to have an @xml:id (i.e., when demonstrating a nested
<org>
that might not be pointed to). I added @xml:id to some of those examples, but not all. (Thus to reinforce that it is optional.)