The StateClock tool and clockcharts

The purpose of this paper is to give a theoretical description of clockcharts, and their implementation in the StateClock tool for COSC4352 students. 1.0 Temporal logic and fair transition systems In the sequel, we use relative quantification where Q is a quantifier (e.g. ∀ or ∃), T is the type of the dummy variable x, R is the range of the dummy variable and P a predicate [Gries, 1993 #369]. For example, means “for all values of an integer variable i, if i is at least as large as 3 then i has property P”. If no range is supplied then it is true. We distinguish between 3 kinds of logical descriptions:SDs, CDs and TLDs. • An SD is a state-description (also called a state-formula). A state-description is a predicate that can be evaulated to true or false in a single state. For example, a description defined by is satisfied in the state (written ). The free variables of are called its alphabet , i.e. . The variable is a dummy variable, and hence is not part of the alphabet. Each variable in the alphabet has a type denoted by . • A CD is a command-descriptions, i.e. a predicate whose alphabet is a set of primed and unprimed variables. The purpose of such a description is to describe a change that occurs between a prestate and a possible poststate under the execution of a command (e.g. a program statement, transition or routine). We will need two names for a variable — the value of the variable in the poststate will be recorded under the primed name , whereas the unprimed name will stand for the value of the variable in the prestate. For example, the command-description where