On the Composition of Interactor Specifications

This paper discusses the composition of interface objects, a concept of direct relevance to user interface software architectures and interface design practice. Composition is discussed formally in the framework of the Abstraction-Display-Controller (ADC) interactor model. The ADC model has been defined as a LOTOS specification template tailored for user interface specification. A transformation of the behaviour expressions describing interactor compositions is defined. The transformation, termed synthesis, maintains the generic structure of the ADC interactor while preserving the meaning of the specification. The correctness of the transformation is proved for several types of compositions. The notion of abstract views of interactors is introduced; it is shown how abstract views may themselves be used as components in composition expressions. Example specification extracts are taken from a case study which was developed to test and improve the ADC interactor model