It is widely held that programming language extensions that support separation of concerns and that are also integrative benefit development, maintenance and reuse of software designs and code. Such is the intent of our Synchronization Units Model (Szumo), which unifies new features for expressing synchronization in a multi-threaded program with existing features of an object-oriented language. However, to make effective use of a language extension, a programmer needs an accurate mental model

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... how new concepts affect and are affected by existing concepts. Moreover, good separation dictates that interactions between these concepts should be understandable at the level of the new concepts. This suggests that the semantics of Szumo should be specifiable as a self-contained partial specification, called a view, and the semantics of its integration with other language features should be specifiable by view composition. To our knowledge, however, view-based approaches have not been applied in specifying the semantics of language extensions. Moreover, devising separable views that serve to simplify comprehensibility of a complex specification is still more of an art than a science. This paper presents a case study in the use of views in structuring a Z specification of Szumo.