You can use cmis:item to query some Content Services object types, and your own custom types, that are outside the CMIS definitions of document, folder, relationship, or policy.
You can find a user, or a set of users, via a CMIS query. For example, the following query will return all information for all users:
SELECT * FROM cm:person
The following query will return the selected fields for users with names like “smith” and “smithers” all users:
SELECT cm:userName, cm:homeFolder FROM cm:person where cm:userName like 'smi%'