Temporal Query Languages Predicates precedes,overlaps,and contains on time intervals. Intersect can be applied on two intervals,to give a single(possibly empty)interval;the union of two intervals may or may not be a single interval. A snapshot of a temporal relation at time t consists of the tuples that are valid at time t,with the time-interval attributes projected out. Temporal selection:involves time attributes Temporal projection:the tuples in the projection inherit their time- intervals from the tuples in the original relation. Temporal join:the time-interval of a tuple in the result is the intersection of the time-intervals of the tuples from which it is derived. It intersection is empty,tuple is discarded from join. Database System Concepts,5th Ed. 24.5 @Silberschatz,Korth and SudarshanDatabase System Concepts, 5 24.5 ©Silberschatz, Korth and Sudarshan th Ed. 5 Temporal Query Languages Predicates precedes, overlaps, and contains on time intervals. Intersect can be applied on two intervals, to give a single (possibly empty) interval; the union of two intervals may or may not be a single interval. A snapshot of a temporal relation at time t consists of the tuples that are valid at time t, with the time-interval attributes projected out. Temporal selection: involves time attributes Temporal projection: the tuples in the projection inherit their time￾intervals from the tuples in the original relation. Temporal join: the time-interval of a tuple in the result is the intersection of the time-intervals of the tuples from which it is derived. It intersection is empty, tuple is discarded from join