Led by Microsoft, IBM, and EMC, OASIS has been working on a modern standard for content management systems, called CMIS. This group has started from a submission made by the above three vendors called CMIS v0.5.
This standard also includes a “binding for REST/Atom”. In layman terms a binding is an adaptation of the abstract standard to a specific network protocol and format.Julian Reschke suggested that we hash out the overlap between CMIS AtomPub extensions and theAtomPub hierarchy-ID. Here’s a summary of the most important areas of disconnect.
CMIS genuinely tries to provide a good AtomPub extension, but fails on at least three counts:
- Link relations defined by CMIS cannot be used by a client that does not understand CMIS. So if you would like to have parent-child relations but don’t want to put a cmis:id attribute (yes, that is a SHOULD level requirement), then you are out of luck. On the contrary, rel=master and rel=detail from hierarchy-ID do not impose any additional requirements.
- There is no way to auto-discover the POST url for a feed. For example, you obtained a list of documents in a folder and now want to add another document to that folder. Without understanding rel=repositoryand cmis:collectionType, there is no way to do that. On the contrary, hierarchy-ID will be understood even by existing AtomPub clients, and these clients will be able to add another item next to the existing document.
- The CMIS spec defines PUT and DELETE methods on an atom:feed type resource (yes, see Section 22.214.171.124 and 126.96.36.199). I would imagine that the CMIS spec would need to go to IETF for doing something like this because they are in effect extending the semantics of the application/atom+xml;type=feed MIME type. No such extraordinary extension is going on in hierarchy-ID and this ID is before the IETF for consideration.
Now, we have every intention of engaging the CMIS to help them understand the consequences of these issues, namely a monolith hanging off a lean protocol that can only be used for content management and improving the use of existing AtomPub metadata for doing simple things like discovering the URL for modifying a feed. Whether that will have any useful outcome is anyone’s guess.