Computer-Based Systems (CBS) are becoming increasingly pervasive throughout society, continually increasing in complexity and cost as they are called upon to fulfil more and more complicated tasks. Unfortunately, multi-million dollar projects often fail because the systems are unreliable, inefficient, insecure and unmaintainable. The National Australia Bank?s $409M software writedown and the failure of the $250M Australian Customs Service Integrated Cargo System are but two recent Australian examples.

Clearly, systems must be built with a range of qualities such as reliability, performance and security, in addition to their required functionality, if they are to be successful. In other fields of engineering, such as aerospace and aeronautical engineering, where similar challenges of multiple conflicting requirements are faced, the approach of design optimisation has been found to be successful. This experience indicates that a similar approach of design optimisation will also help to meet the challenges presented by the quality requirements of CBSs.

This paper advances our work on design optimisation with an exploratory optimisation method that derives an architecture that best satisfies the system?s quality requirements. The method allows a designer to explore possible architectures by repeatedly applying evolutions to an initial architecture, with the quality attributes of each architecture being collected throughout and providing feedback that guides the designer to the final optimal architecture.

A prototype tool is also presented that implements this architecture-based optimisation method, using Avolution?s industry-proven ABACUS- toolset.