On P – Normal Form of Parallel Program

In the last few years parallel programs are intensively studied. But when parallel program is investigated, it is assumed, that only one “cobegin … coend” (“fork … join”) operation is used (see e.g. [1,2]) in the program schemata. In the paper we introduce the notion of the equivalence relation between parallel programs and then it is proved that it is sufficient to study properties of parallel programs only with one “cobegin … coend” program connective.