CMIS has built-in support for hierarchies through CMIS Folder and CMIS Document.
Content Services maps its out-of-the-box types cm:folder and cm:content (as defined in the domain model) to CMIS Folder and CMIS Document, respectively. A folder can contain a mixture of documents and folders, allowing for a hierarchy of documents to be built. Through this, CMIS supports an implicit notion of parent to child, to which is used by Content Services to map its child association. Subtypes of cm:folder and cm:content are exposed as subtypes of CMIS Folder and Document, respectively.