Temporal logic queries on Datalog and negated Datalog programs are stu
died, and their relationship to Datalog queries on these programs is e
xplored. It is shown that, in general, temporal logic queries have mor
e expressive power than Datalog queries on Datalog and negated Datalog
programs. It is also shown that an existential domain-independent fra
gment of temporal logic queries has the same expressive power as Datal
og queries on negated Datalog programs with inflationary semantics. Th
is means that for finite structures this class of queries has the powe
r of the fixpoint logic.