I never quite understood the need to enlist the help of cmis:id on atom:link elements, which is called for in Section 3.2 of AtomPub bindings for CMIS. There are prominent signals about its importance, but no justification of its needs in AtomPub link relations.
For example, here’s what a atom:link element would look like if generated by a CMIS server:
<atom:link rel="repository" cmis:id="..." href="..." type="application/atomsvc+xml"/>
CMIS AtomPub extensions make the presence of cmis:id mandatory, which is yet another encumbrance on using existing AtomPub clients.
Even though this requirement looks silly, I was disappointed that the editors of the spec did not follow up with examples that showed the use of cmis:id. For example, the document entry example in the specification package does not use cmis:id on any of the links including for relations introduced by CMIS.