A Rationale-based Model for Architecture Design Reasoning

3.1. What is design rationale?
3.1 What is design rationale?
According to the Cambridge dictionary [127], a rationale is a reason or an intention for a
particular set of thoughts or actions. When architects and designers make design decisions,
what do they consider as a reason or an intention? Should a requirement or a constraint be
considered a reason for a design? Or is it some generic justification that allows designers
to judge that a design is better than its alternatives? There are many ways to interpret
design rationale. A common understanding is using design rationale to explain“why”
design artefacts exist.
An interpretation of design rationale depends on the perspectives of the researchers.
Moran and Carroll suggested that design rationale are reasons to express the purposes of
the designed artefacts with their contextual constraints on realising the purposes [103].
Design rationale are the logical reasons to justify a designed artefact. According to Conklin
and Burgess-Yakemovic [24], design rationale can have the characteristics of recording
the history of how a design comes about through recording logical reasoning to support
future reference. Carroll and Rosson [18] suggested that design rationale can be viewed
as psychological claims that are embodied by an artefact whereby design deliberations
through evolution can be assessed. Maclean et al. [97] claimed that design rationale can
be a description of the design space and used to deliberate design decisions.
Depending on the information need and how that need is to be satisfied, design rationale
can exist in many different forms [33]. One way of looking at design rationale is by
its level of use:
• No Explicit Rationale - the design reasoning process is not employed in a conscious
and systematic way. Instead, it is intuitive to the designer. In this case, design
rationale are not captured. When asked to explain the design, designers either remember
the rationale from the past or reconstruct the design rationale by deduction
[157, 53].
• Informal Rationale - this technique is used by designers to capture design reasoning
in an unstructured way such as notes. The choice of which rationale to record is
ad-hoc and the level of details of the documentation varies [33, 157].
• Template Based Rationale - design rationale is captured in a systematic manner using
pre-defined templates incorporated in the design process. Examples are Architecture
Decision Description Template [170] and Views and Beyond [23].
• Argumentation Based Rationale - design decisions are rationalised by using arguments
for each alternative. Argumentation-based models focus on how the ideas and
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