The CMIS protocol was designed to give easy access for uploading/retrieving documents and folders.
Can the CMIS protocol be used to retrieve node content in Alfresco? For example is the following query valid? This tries to retrieve all tasks from the repository, which is not a folder or document.
SELECT * FROM bpm:task
Yes, it's a valid query in CMIS and will retrieve the content you're looking for in Alfresco.
The Content Management Interoperability Services protocol isn't designed to operate on Documents and Folders: as its name states, it's all about Content. In the CMS's world, content is generally (and generically) identified as a unit of information with a type and metadata attached to it. In this sense, a bpm:task in Alfresco becomes a Content item in CMIS.
Documents and Folders happen to be also Content, and being somehow special types of content they have dedicated APIs in CMIS on top of the generic ones.
