And events may have multi-valued attributes...
Examples
- S: (category = book) & (category = antiques) & (title = Hamlet )
- E: ( (category, {book,antiques}), (title, Hamlet), (author, Sheakespeare),
Conjunctions of Subscriptions
- S1:(category = book) & (title = Hamlet )
- S2: (category =antiques& (title = Hamlet )
- S: S1 & S2
A single event generates
- (n1+1) ? … ? (ni+1) ? ...? (nd+1) point queries!
- ni is the number of values for attribute i