A two-level temporal logic for evolving specifications

Traditional information system specifications are fixed: the rules of the system are frozen at specification time. In practice, most systems have to change their rules in unexpected ways during their lifetime. We present here a simple variant of a temporal logic that deals with specification evolution. It is a linear time temporal logic with two levels of time: intervals, interrupted by mutations (changes of rules), which compose lives of the system. We present a complete axiom system and complexity results, which show a large compatibility with classical linear temporal logic.