A Rationale-based Model for Architecture Design Reasoning

5.3. Survey findings
previous design decisions (Table 5.13), it can be argued that the availability of design
rationale can improve this process. Design rationale is considered an important input to
impact analysis because if the knowledge about the factors that may have influenced the
original design decisions is available, designers do not have to spend a large amount of time
to understand the existing design and the potential ramifications of any changes [128].
Table 5.14: Frequency of Performing Impact Analysis
Never
Always
1 2 3 4 5
No of Respondents 0 4 13 29 19
Percentages 0.0 6.2 20.0 44.6 29.2
We were also interested in determining the importance of the tasks performed in impacts
analysis, some of which require design rationale support. The importance of such
tasks during impact analysis can be considered as an indicator of the need or usefulness
of design rationale to improve this activity and subsequently the maintenance process. To
investigate this issue, there was a multiple-items question on the importance of various
tasks. Table 5.15 shows what the respondents think of the importance of the factors. In
carrying out impact analysis, most respondents trace requirements. They analyse the design
and design rationale based on the available design specifications. In the analysis, they
are concerned about the feasibility of the implementation, its costs and risk. They are
also concerned that the new design is consistent with the constraints and the assumptions
of the existing system.
Table 5.15: Importance of Each Impact Analysis Task
Not
Very
Important
Important
1 (%) 2 (%) 3 (%) 4 (%) 5 (%)
(a) Analyse and trace requirements 1.5 0.0 10.3 39.7 48.5
(b) Analyse specifications of previous design 1.5 10.3 19.1 35.3 33.8
(c) Analyse design rationale of previous design 1.5 11.9 32.8 32.8 21.0
(d) Analyse implementation feasibility 1.5 1.5 8.8 41.2 47.0
(e) Analyse violation of constraints and assumptions 1.5 8.8 25.0 41.2 23.5
(f) Analyse scenarios 1.5 7.6 16.7 36.4 37.8
(g) Analyse cost of implementation 0.0 10.3 13.2 30.9 45.6
(h) Analyse risk of implementation 0.0 4.4 5.9 32.4 57.3
Given the results, it is obvious that architects and designers often have the need to
refer to design documentation for impact analysis. Some of information that they use
require design rationale support such as understanding design assumptions, constraints,
cost and risk. However, this information are not necessarily organised in a way that can
be easily used for impact analysis. Additional factors that have been discovered in this
survey can contribute to the difficulties in impact analysis: (a) architects can forget the
reasons behind the design; (b) the person doing the maintenance may not be the original
designers.
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