Abstract Specification in Object-Z and CSP

specification in Object-Z and CSP Graeme Smith and John Derrick Software Verification Research Centre, University of Queensland 4072, Australia phone: +61 7 3365 1625 fax: +61 7 3365 1533 [email protected] Computing Laboratory, University of Kent, Canterbury, CT2 7NF, UK. [email protected] Abstract. A number of integrations of the state-based specification language Object-Z and the process algebra CSP have been proposed in recent years. In developing such integrations, a number of semantic decisions have to be made. In particular, what happens when an operation’s precondition is not satisfied? Is the operation blocked , i.e., prevented from occurring, or can it occur with an undefined result? Also, are outputs from operations angelic, satisfying the environment’s constraints on them, or are they demonic and not influenced by the environment at all? In this paper we discuss the differences between the models, and show that by adopting a blocking model of preconditions together with an angelic model of outputs one can specify systems at higher levels of abstraction. A number of integrations of the state-based specification language Object-Z and the process algebra CSP have been proposed in recent years. In developing such integrations, a number of semantic decisions have to be made. In particular, what happens when an operation’s precondition is not satisfied? Is the operation blocked , i.e., prevented from occurring, or can it occur with an undefined result? Also, are outputs from operations angelic, satisfying the environment’s constraints on them, or are they demonic and not influenced by the environment at all? In this paper we discuss the differences between the models, and show that by adopting a blocking model of preconditions together with an angelic model of outputs one can specify systems at higher levels of abstraction.