Besides describing strategies by ALGOL-like programs we may also want to describe the laws of change of the situation by such programs. In doing so we must take into account the fact that many processes are going on simultaneously and that the single-activity-at-a-time ALGOL-like programs will have to be replaced by programs in which processes take place in parallel, in order to get an epistemologically adequate description. This suggests examining the so-called simulation languages; but a quick survey indicates that they are rather restricted in the kinds of processes they allow to take place in parallel and in the types of interaction allowed. Moreover, at present there is no developed formalism that allows proofs of the correctness of parallel programs.