Headers and RDF rules can be added to each database.
I extract itinerary information from email that I get from Sun's travel service. This creates RDF statements that indicate where I'm travelling and when. Then...
If I'm travelling to an airport, and
I have an address book entry for that airport, then
Associate that address book entry with the flight in my date book.
{ :app a palm:Appointment . :con a palm:Contact . :app it:arrive :s . :con ab:id :s } log:implies { :app p:who :con } .