A temporal relational algebra based on multiple time-lines

Abstract

A clocked temporal relational algebra, called /spl Rfr/, which supports temporal relations based on multiple time-lines is proposed. Temporal relations are defined over clocks which are subsequences of an assumed global time-line. The algebra is a consistent extension of the relational algebra, and it includes a number of temporal operators to combine data based on different time-lines. The meaning of an operation of /spl Rfr/ depends on the clocks of the relations involved in the operation as well as the relations. We outline a formal interpretation of expressions of /spl Rfr/, and sketch a naive expression evaluation method.