Temporal Relational Calculus
Two-sorted first-order logic
Temporal Relational Calculus (TRC) is a temporal query language extending the relational calculus. In addition to data variables and quantifiers ranging over a data domain (a universe of uninterpreted constants), temporal relational calculus allows temporal variables and quantifiers ranging over an appropriate time domain .
A natural temporal extension of the relational calculus allows explicit variables and quantification over a given time domain, in addition to the variables and quantifiers over a data domain of uninterpreted constants. The language is simply the two-sorted version (variables and constants are temporal or non-temporal) of first-order logic over a data domain D and a time domain T.