Overview

The structure of this section is based on Figure . There are three sections, each of which contains ten sections. The three top-level sections classify queries according to the output. Thus, the output from a query may have either only an explicit-attribute value component (O1), only a valid-time component (O2), or it may have both (O3).

Each top-level section contains the same ten sections. These divide queries based on a single, distinguished valid-time selection predicate². The predicate is of the format arg₁ op arg₂ where op is a comparison operator which may (or may not) be duration-based. One argument is the valid time of tuples in the argument relation. The other argument may be of event, interval, or element type; orthogonally, it may (or may not) be computed from existing valid times in the argument relation. This results in a total of ten classes (the combination of duration-based predicates and event arguments is omitted).

		 (S1) 		 (Duration, Interval, Computed) 

(S2) 		 (Duration, Interval, Other) 

(S3) 		 (Duration, Element, Computed) 

(S4) 		 (Duration, Element, Other) 

(S5) 		 (Other, Event, Computed) 

(S6) 		 (Other, Event, Other) 

(S7) 		 (Other, Interval, Computed) 

(S8) 		 (Other, Interval, Other) 

(S9) 		 (Other, Element, Computed) 

(S10) 		 (Other, Element, Other)