Specifying temporal requirements for distributed real-time systems in Z

It is becoming widely accepted that along with the formal specification of functional properties it is necessary, in some systems, to provide a specification of timeliness properties. Unfortunately, the main methods which would seem to provide this form of requirement appear to be targeted at specifying communication protocols. While it is possible to adapt these methods for simple timeliness properties, their use for describing constraints on distributed systems would be impractical This paper introduces a set of definitions for the Z specification language which enables timeliness properties to be represented formally. The toolkit provides a method of framing the temporal specifications, which enables these specifications to be looked at from multiple viewpoints, a feature which facilitates the specification of distributed systems. A formal basis for the toolkit is given, together with justification for the features of the model of time that has been adopted.