On the use of specification styles in the design of distributed systems

The term architecture denotes in this paper an abstract object that defines a set of requirements for a class of products, and that can be used to derive from it various more concrete objects, called (product) implementations. We assume that an architecture is expressed in a formal description language. The paper argues that in practice any architecture of more than elementary complexity, and thus its formal description, needs to be structured in order to keep it comprehensible and to efficiently express its functionality. This structuring may introduce implementation-oriented elements in the architecture, despite the fact that in principle the architecture should be implementation independent: i.e., it should be just a definition of the abstract object's external functionality.