Partial ordering models for concurrency can be defined operationally

Labelled rewriting systems are shown to be powerful enough for defining the semantics of concurrent systems in terms of partial orderings of events, even in the presence of non standard operators like N that is not expressible by means of concurrency and sequentialization. This contrasts with Pratt's claim.⁽¹⁾ The main operators proposed by Pratt are used here to construct terms denoting concurrent systems, the behavior of which consists of partially ordered multisets defined operationally.⁽²⁾ Fully abstractness of the denotational semantics as defined in Ref. 1 with respect to the operational one is finally proved.