D.3.3 ALGORITHMS FOR INCREMENTAL ... - SecureChange

The feedbacks provided by the ATM expert P5 and P9 during the second workshop
indicate that the representation of evolution rules can be applied to model evolution in
the ATM domain. The experts pointed out that since ATM systems are complex systems
it might be difficult to predict all possible evolutions and represent them as after
requirement models. Thus, they suggested to adopt an incremental approach to identify
the possible evolutions. Moreover, the experts reported that the probability of evolution
is difficult to determine. They also pointed out that qualitative parameters are associated
with evolution in the ATM domain rather than the probability of evolution.
SC4:The approach to model and reason on requirements evolution can be easily understood
by ATM domain experts.
The graphical representations for evolution rules illustrated in Figures 1(a) and Figure
1(b) were presented to the ATM experts during WS1 the first workshop. The ATM
experts were asked which graphical representation they prefer and they preferred the
tree-like representation. They were also asked if the find intuitive the graphical representation
and they agreed that the graphical representation could be easily understand
by them. This answer is also supported by the fact that the domain experts suggested
modifications to the requirement models that were the after models of an observable
evolution rule, explained their rationale, or asked relevant questions about some detail
in the models. This indicates the graphical representation and the before and afterevolution
requirements models were comprehensible for the domain experts.
6 Lessons Learnt and Conclusions
This paper has presented the results of a qualitative user study about requirements evolution.
The objectives of the study were to gain in-depth understanding of the change
management process adopted by Air Navigation Service Providers when a new tool
such as the AMAN is introduced, and to investigate the role that the approach to model
and reason on requirements evolution can play in such process. The study was mainly
built on semi-structured interviews with a high degree of discussion between the requirement
analysts and ATM domain experts, and on focus groups meetings. This approach
has allowed the requirement analysts to understand the change management
process adopted by Air Navigation Service Providers.
The user study also has provided useful insights into the weaknesses and advantages
of our approach to requirement evolution’s modeling and reasoning. Moreover,
we have learnt important lessons about the aspects to consider during research design.
We summarized the main findings in what follows.
6.1 Results Related to the approach to Requirements Evolution
A lesson learnt from the user study is that the most challenging step of our approach
to requirement evolution is Evolution Elicitation. Regarding the Evolution Elicitation
phase, not all after requirement models for an observable rule can be foreseen in advance.
Estimating the probability of evolution of after requirements models is not a
trivial process. The tree-like representation for evolution rules is easy to understand
but its intuitiveness can be undermined if the before and after evolution requirements
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