Syntax and semantics of Procol
A metric semantics of the parallel object-based programming language Procol is introduced. It is divided into three layers , a global layer, an object layer, and a statement layer. At the global level, the sequence in the interactions between the objects (represented in the object layer) is described. The object level expresses the abstract behavior of one object, i.e., only those aspects that are relevant for the outside world. It specifies the interactions an object is willing to perform, and also in what sequence it is able to do so. The statement layer is the most concrete one. It gives a direct representation of a Procol program. In this layer all constituent statements of a program are still recognizable. It forms the basis for the two higher layers, containing all possible sequences of communication statements needed at the object and global layer. Two transformation functions between these three levels can be defined, one from the statement layer to the object layer, and one from the object layer to the global layer. In this paper only the latter transformation will be introduced. New in our approach are a new denotation of the global layer, and a more intuitive transformation to this layer.
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