A Rationale-based Model for Architecture Design Reasoning

3.5. How well design rationale methods work?
arises when the design rationale system forces users to encode ideas before they are ready
to make the decision thereby causing a premature commitment. Argumentation-based
tools require users to either encode the deliberation when the ideas are still premature
causing subsequent changes to be made. Otherwise, the users would have to recall the
deliberation process and then record the full argumentation after a final decision has been
made. Neither way is convenient to practitioners.
In an empirical study, it was suggested that the design rationale constructed using
the QOC method is insufficient [76]. A number of design rationale issues were identified:
(a) not all information was captured because analysts had not reported the facts; (b)
QOC lacked weighted assessments since there is no quantitative analysis to indicate why
a solution is better than its alternatives; (c) users of QOC have misconceptions of the
captured information. In conclusion, it was found that some designers extensively use
design rationale but less than half of the design rationale questions could be answered by
the QOC-based documents.
Herbsleb and Kuwana [62] pointed out that the why question may often be used to
establish the context of the design when it is unclear. However, in the current practice
the why question are seldom asked because they generally cannot be answered using the
current tools.
Although design rational methods have laid the foundation for design reasoning, most
of them still have issues from a usability perspective. Learning from these issues, a set of
criteria for a successful design rationale implementation are summarised below:
• Effective Capture of Design Rationale - the argumentation-based models capture
both the reasoning and the design rationale argumentation structure. The argumentation
structure is time-consuming and difficult to trace. Therefore, it should be
simplified without losing key design rationale information.
• Effective Communication of Design Rationale - designers want to know the issues, the
justifications, the potential alternatives and what design elements a decision affects.
The necessity to replay the deliberation process as suggested by the argumentationbased
models is thus reduced. The issues in argumentation-based models are the
over representation of deliberation and under representation of its relationship with
design artefacts.
• Design Artefact Focus - requirements and design objects specifications are used
to support system evaluation and maintenance. Therefore, design rationale must
explain design artefacts contained in these specifications in order to be useful.
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