Handling Conflicts in Aspectual Requirements Compositions - Transactions on Aspect-Oriented Software Development - page 161

Table 15. Final consistency ratio for all pairwise matrices

Pairwise matrices Consistency Index (CR)

Table 7 (Contribution) 0.02

Table 8 (Passenger) 0.07

Table 9 (System Owner) 0.04

Table 10 (Developer) 0.05

Table 11 (Stakeholders Importance) 0.01

Table 12 (Criteria Weights) 0.00

4.3 A Summary of Our Initial Experiments with AHP

In our first attempt to use the AHP method to manage conflicts within the AORA
approach [6], we tried to handle all the concerns in the whole system at once.
However, we soon realised that we needed to first resolve conflicts with respect to
particular match points. The very first problem we had to solve was to identify the set
of alternatives (based on the problem under study) as well as the list of criteria (from
the template in Table 1) that could bring useful information to the conflict resolution
process. While the alternatives are the required concerns in a given match point, the
criteria are a subset of the fields in the template.
Initially, the fields selected were Sources, Type, Contribution, Classification and
Importance (at that time, Importance was stakeholder independent). These
experiments led us to change the “Importance” element to be stakeholder dependent,
since different stakeholders may have different interests on each concern. This
allowed us to be able to differentiate stakeholders' interest on each alternative.
Another decision that is worth noting is that Sources, Type and Classification have
been identified as having no effect in the solutions obtained. While Sources is a string
and it is virtually impossible to associate a degree of trust to it, Type and
Classification ranges are crisp binary values and therefore there is no indecision
associated with them.
During the process refinement, we realised that the Contribution field, which
initially also looked like a binary crisp type, could have an impact on the results
obtained. The explanation is that we could “quantify” the strength of the negative
contributions. For example, considering two concerns A and B, contributing
negatively to each other, we can associate a degree of strength to this relationship of
the kind “highly negative”, “negative”, “not too negative”, for example.
After several experiments, the criteria chosen were Importance (one value for each
stakeholder) and Contribution.

5 AHP Versus Weighted Average

The AHP approach proved to produce useful information and since it ensures logical
consistency, contributes to the developers trust on the results. Moreover, the AHP
pairwise structure provides the means to express, easily, preferences between criteria
(e.g., passenger is less important than system owner) and as well as between
alternatives for each criterion (e.g., response time is much more important than
accuracy for passenger). Nevertheless, it is rather cumbersome in terms of requiring