Whoever retrieves a ::com::sun::star::sdb::OfficeDatabaseDocument should be aware of
life time issues, since a document needs to be closed when nobody needs it anymore.
This implies that clients of a document need to ensure that as soon as they don't
need, they invoke ::com::sun::star::util::XCloseable::close .
Since this can be done by multiple clients, every client is additionally required
to register itself as ::com::sun::star::util::XCloseListener at
the document, to prevent some other client closing the model while it's still needed
by the first client.