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A Rationale-based Model for Architecture Design Reasoning

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9.5. Discussion<br />

9.5 Discussion<br />

In the empirical study (Section 7.2.4), it was found that the ability to trace architecture<br />

design and its design reasoning are important in software architecture. It enables an architect<br />

to reason with complex design and to support software maintenance if the knowledge<br />

cannot be remembered.<br />

As commented by the experts who participated in the empirical study, the usefulness<br />

of this method depends largely on the cost-benefit of its implementation and how well an<br />

organisation adopts it. The cost of capturing the traceability relationships must be kept as<br />

low as possible, and the capture process itself must not impede the design process. This is<br />

yet to be tested in large-scale projects but it is anticipated that the benefit would exceed<br />

the cost in such projects. There is a major assumption in employing this method: the<br />

traceability relationships are captured perfectly and the design reasoning are documented<br />

thoroughly. This assumption depends on how well an organisation adopts the method and<br />

if the architects involved believe in design knowledge retension and use it diligently.<br />

9.6 Summary<br />

In this chapter, we have discussed the need <strong>for</strong> traceable design reasoning. We have identified<br />

three ways to trace an AREL model. Forward tracing supports impact analysis.<br />

Given a requirement, the design objects and design rationale that are directly and indirectly<br />

depended on and impacted by it can be traversed. Backward tracing supports<br />

root-cause analysis. Given a design element, its causes such as requirements, assumptions,<br />

constraints and design rationale can be traversed. Evolution tracing supports the<br />

traceability through the evolution of an architecture element or an architecture rationale.<br />

These methods facilitate the understanding of architecture design by allowing architects<br />

to trace the design with reasoning support.<br />

AREL and its traceability are supported by the AREL Tool and the UML tool, Enterprise<br />

Architect (see Chapter 11 <strong>for</strong> details). The architecture viewpoints which classify<br />

the architecture elements in AREL can be used to scope the trace results. Using the EFT<br />

system as a case study, we have demonstrated how the architecture design can be traced.<br />

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