Divergence models for atomized statements and parallel choice

The authors study the semantics of a language containing the usual operators of sequential composition, choice and parallel composition. It contains furthermore an atomizer which causes a statement to behave like an atomic action and thus increases the grain size of the parallelism. It follows that `atomic´ actions can be non-deterministic, deadlocking and even diverging. They set out to define a semantics that is an extension of the usual process algebra models. There are several possibilities for this extension (in particular for the choice operator) and they consider the so-called parallel choice. The paper includes the definition of an operational semantics, a denotational semantics and an outline of the proof of correctness. The paper is directed towards the modelling of the divergence. This is already non-trivial due to unbounded nondeterminism introduced by the atomizer: they have to extend the standard stream model. The proof of correctness requires a new technique in which they introduce orderings on proofs of transitions. They also provide an algebraic characterization of the finite part of the language