In recent years, interactive systems developers have increasingly included usability engineering and interaction design as an integral part of software development. With recognition of the importance of usability come attempts to structure this new aspect of system design, leading to a variety of processes and methodologies. Unfortunately, these processes have often lacked flexibility, completeness and breadth of coverage, customizability, and tool support. This thesis shows the development of a process model, that we call LUCID/Star*, which addresses and overcomes the characteristics lacking in existing methodologies and an evaluation of its application in a real-world development environment. To demonstrate the goal of this thesis, we have used a combination of empirical and analytical evidence.

The (LUCID/Star)* process model for usability engineering grew out of the examination, adaptation, and extension of several existing usability and software methodologies. The methods that most greatly impacted the creation of (LUCID/Star)were the LUCID Framework of interaction design, the Star Life Cycle of usability engineering, and the Waterfall and Spiral models of Software engineering. Unlike most of these, we have found that a sequence of cycles (each of which produces a product evolution) is a more effective analogy for the interaction development process. A sequence of cycles is more modular and makes it easier to focus on each cycle separately. Working with Optim Systems, Inc. in Falls Church, VA we instantiated the process model and introduced it as a process to develop a web-based device management system. (LUCID/Star) performed remarkably in the Optim case, overcoming the tight constraints of budget and schedule cuts to produce an excellent prototype of the system.