Generalized logical operators for temporal languages

Previous proposals of temporal languages have used the standard TRUE/FALSE model of Boolean and comparison operators. Since this standard binary model introduces ambiguity as to which time value is desired, expressing nontrivial temporal conditions in these languages can be quite complicated. The authors' model overcomes this problem by generalizing the TRUE/FALSE model into one that uses sets of time intervals. The set-valued temporal logic satisfies the properties of the normal Boolean logic. The proposed logic can be very useful to different applications of temporal languages. Database query languages are used to demonstrate the effectiveness of the set-valued logic. The basic features of a relational-calculus query language based on the set-valued logic are presented. Applicability of the logic to relational-algebra query languages is discussed.<>