Chapter 3 : Software Architecture Modelling : Bridging Two Worlds Using Ergonomics and Software Properties

The process of designing and constructing user interfaces is critical for building systems that satisfy the customer's needs, both current and future. This process includes the original design of the interface, the implementation of the system, and the modifications to the operational system. These modifications are endemic in interactive systems. Since the user interface can account for approximately 50 per cent of total life cycle costs [Myers 89], the software engineer has a vested interest in constructing a user interface that both satisfies the customer and is constructed using the best available tools and techniques. In addition, the increasing complexity and size of software systems require sound engineering principles and frameworks to formally structure the design process into multiple but consistent perspectives. Tools that support the development of user interfaces vary widely in complexity and power ranging from user interface toolkits to user interface generators. Although powerful, user interface generators cannot produce everything. Therefore, the user interface must be tuned to the specific case at hand. In turn, customization requires programming, and good programming practice necessitates an architectural framework such as PAC-Amodeus. PAC-Amodeus is an hybrid multi-agent software architecture model that represents the organization of the components of an interactive software. As any architectural framework, it consists of the description of an organisation of computational elements and their interactions [Shaw 95]. Software tools for the construction of user interfaces will not eliminate architectural issues as long as the construction of user interfaces requires programming. Developers and maintainers of interactive systems need to rely on models: • for identifying software components, • for organising their interconnections, • for reasoning about components and interconnections, • for verifying ergonomic and software properties, • for modifying and maintaining them in a productive way. Software architecture may also be used to communicate a design solution to another development team such as the programmers. In this case, the description must be unambiguous. A model may reduce misinterpretation risks. In this chapter, we present an agent-based architectural model PAC-Amodeus, for the purpose of assessing software designs. In order to clarify the role of a software