D.3.3 ALGORITHMS FOR INCREMENTAL ... - SecureChange

Evolution
Elicitation
Probability
Estimation
Reasoning
Decision
Fig. 2. Requirements Engineering process for Change/Evolution Management
The elicitation of evolution rules is the first step of the change management illustrated
in Fig. 2. The process consists of four major steps, namely Evolution elicitation,
Probability Estimation, Reasoning, and Decision [14].
STEP 1 Evolution Elicitation. The goal of this key step is to extract evolution rules
from a description in natural language of the possible requirements evolutions.
In order to do that, first, statements about changes are identified. Then, changes
are clustered into mutually exclusive groups. Then, each group will represent an
After i requirement model.
STEP 2 Probability Estimation. Based on the evolution rules identified in the previous
step, this step relies on methods like Analytic Hierarchy Process (AHP) to identify
the evolution probability for each possible evolution After i of an observable evolution
rule. The probabilities are then validated with stakeholders(and/or domain
experts) using a game-theoretic approach [15] to ensure that they are meaningful.
STEP 3 Reasoning. Based on the representation of an evolving requirement model as
a set of controllable and observable rules, it is possible to compute two quantitative
metrics called maximal belief and residual risk that intuitively measure the usefulness
of a model element (or a set of elements) after evolution. In fact, the maximal
belief tells whether a design alternative is useful after evolution, while residual risk
quantifies if a design alternative is no longer useful.
STEP 4 Decision. Decision makers take the analysis’ outcome to choose the optimal
design for the next development phases. Depending on the kind of analysis, different
“optimal” criterion can be applied. For instance, a selection criterion for the
analysis is: “higher max belief and lower residual risk”.
4 Research Methodology
Many different assessment methodologies can be used for validation with domain experts.
For this study, we have mainly used qualitative techniques. Qualitative research
consists of an application of various methods of collecting information, mainly through
focus groups and interviews. Interviews are commonplace techniques where domain
experts are asked questions by an interviewer in order to gain domain knowledge and
it is the most widely used method of finding out what users want [8]. Focus groups
bring together a cross-section of stakeholders in an informal discussion group format.
The user study has involved twelve participants having different background and roles
as summarized in Table 2. P1, P2, P3 and P4 played the role of requirement analyst
and observer. Requirement analysts were responsible for the organization of the user
study and for the analysis of the results. The observers were responsible to record the
meetings and take notes during the execution of the study. The other participants were
ATM domain experts who participated to the semi-structured validation of the proposed
approach to model and reason on requirements evolution.
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