Places:RDF Wrapper
From MozillaWiki
Introduction
To build non-tree UI, RDF will be used until a suitable replacement template builder is supplied.
A RDF DataSource service is created that registers a the result of a query and the serialization of its queries. The serialization is used to build a RDF Resource which represents the RDF "container" that pieces of UI can be rooted on, e.g:
<xul:menu datasources="rdf:places" ref="place:query=blah"/>