XCD – Simple, Modular, Formal Software Architectures

Connector-Centric Design (XCD) is a new approach for specifying software architectures that focuses on the use of complex connectors. In XCD simple interconnection mechanisms like procedure-calls, event-buses, etc. are abstracted and components take a second place. XCD aids the clear separation in a modular manner of the highlevel functional, interaction, and control system behaviour, thus increasing the reusability of both components and connectors. As such, XCD allows designers to experiment with different interaction behaviours (connectors), without having to modify the functional behaviour specifications (components). It further allows designers to experiment with different control behaviours (“role strategies”), without modifying components or connectors. Inspired by JML, XCD follows a formal, Design-byContract approach, describing behaviour through simple pre/post-conditions, which should make it easier for practitioners to use. XCD extends Design-by-Contract so as to separate contracts into functional and interaction subcontracts, and so as to allow service consumers to specify their own contractual clauses. The specifications of XCD connectors are completely decentralized (e.g., no “connector glue”) to facilitate their realization and their refinement for further formal analyses. Keywords-Software architecture; Modular specifications; Separation of functional interaction and control behaviours; Design by contract.