A Rationale-based Model for Architecture Design Reasoning

3.2. Why do we need design rationale?
their relations are to be represented [72]. Examples of such models are PHI [99],
gIBIS [26] and DRL [94].
• Quantitative Rationale - another type of model is by way of quantifying costs and
benefits of design alternatives in the decision making process. Examples of such
techniques are CBAM [4] and AHP [152].
As the level of sophistication of design rationale changes, so are the amount of information
captured, the complexity of its implementation and the associated costs. It would
therefore be important to examine the reasons for capturing design rationale to assess
their usefulness.
3.2 Why do we need design rationale?
Researchers in the area of design rationale have argued that there is a need to improve
the design decision making process to capture, represent and reuse design rationale lest
that they might be lost. Perry and Wolf [119] suggested that as architecture design
evolves, the system is increasingly brittle due to two problems: architectural erosion and
architectural drift. Both problems may lead to the violations of the architecture design
over time because the underlying rationale is not available to support the architecture
design. Bosch suggested that architecture design decisions are crossing-cutting and intertwined,
so the design is complex and prone to erroneous interpretations without a first-class
representation of design rationale [11]. As such, the design could be violated and the cost
of architectural design change could be very high and even prohibitive. Kruchten et al.
suggested that architecture knowledge consists of the architecture design and its design
rationale [86]. They identified a number of use cases for design rationale in the architecture
design process.
The reasons for capturing and using design rationale are twofold: using design rationale
to support the design process; and using design rationale to support the maintenance
activities. The following is a summary of why design rationale can be useful:
Supporting the Design Process
• Deliberating and Negotiating Design - by making explicit the main decision making
elements, Dutoit and Peach suggest that design rationale facilitates negotiations
among developers by systematically clarifying the issues and possible options, and
evaluating them against a well-defined criteria [33]. Olson et al. have shown that
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