It is possible to add your own namespaces within CQ. Just as there are predefined namespaces such as cq, jcr and sling, you can have a namespace for your repository metadata and xml processing.
Go to the node type administration page, http://<host>:<port>/crx/explorer/nodetypes/index.jsp. The right-most button at the top of this pages is Namespaces. Clicking that button will open a pop-up window containing the namespace administration page. At the bottom of the page is the New button use to add a namespace.
The namespace follows the XML namespace convention. There is the id in the form of a URI and the prefix associated with that id.