[Zope] using ZCatalog to search multiple data containers

Something that has been bothering me with this whole ZCatalog thing is how do I search things other than the Zope ODB. More importantly how do I combine a search that works with the ZCatalog with things from databases. Lets say I have a database driven FAQ. How do I put a single search field on a site that finds normal DTML documents as well as parts of the FAQ?