A Rationale-based Model for Architecture Design Reasoning

6.8. Summary
issues with AREL. In Table 6.1, we recapitulate these usability features and describe how
AREL has been implemented to fulfil them.
Table 6.1: An Analysis of the Usability Features in AREL
AREL Implementation Notes
Effective capture of Yes Design rationale can be captured in ARs during the design process,
design rational
and AEs are captured as part of the architecture design.
Effective communication of Yes AREL uses a UML graphical representation to communicate
design rational
the causal relationships between design rationale and design objects.
Design Artefact Focus Yes AE can represent requirements, assumptions, constraints,
and design objects. They are classified by different architecture viewpoints.
Traceability and Yes AREL provides tool support to carry out tracing and
Impact Analysis
impact analysis.
Comprehensive Design Rationale Yes AR contains qualitative and quantitative design
rationale as well as alternative design options.
Common Tool Support Yes A commercially available UML tool can be used to support AREL.
The way AREL is structured is simpler than the argumentation-based methods because
design deliberations are not captured. Instead, design rationale are encapsulated in an AR
node and the various kinds of design reasoning are captured with templates. Therefore,
it is simpler for architects to record and use them. The usefulness of the design rationale
captured by AREL is further explored in an empirical study in Chapter 7. Other usability
features are discussed as follows: traceability in Chapter 9, impact analysis in Chapter 10
and tool implementation in Chapter 11.
6.8 Summary
In this chapter, we have introduced the AREL model to represent the architecture design
rationale, architecture design elements and their causal relationships. We use a conceptual
model to describe the high-level requirements of AREL. We distinguish between motivational
reasons and design rationale. The AREL model is characterised as follows:
• Architecture element - an architecture element is an input and/or an output of an
architecture decision. It can be a motivational reason to a decision, and it can also
be an outcome of the architecture decision. Architecture elements are classified by
viewpoints.
• Architecture rationale - an architecture rationale represents the reasons behind an
architecture decision. It contains the qualitative rationale, the quantitative rationale
and alternative designs.
• Directional link between architecture elements and rationale - architecture elements
that are used as inputs into the decision and the architecture elements which are
created as the outcome are linked to the architecture rationale
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