  Goal-oriented requirements variability modelling has established the
understanding for adaptability in the early stage of software development-the
Requirements Engineering phase. Goal-oriented requirements variability
modelling considers both the intentions, which are captured as goals in goal
models, and the preferences of different stakeholders as the main sources of
system behaviour variability. Most often, however, intentions and preferences
vary according to contexts. In this paper, we propose an approach for a
contextual preference-based requirements variability analysis in the
goal-oriented Requirements Engineering. We introduce a quantitative contextual
preference specification to express the varying preferences imposed over
requirements that are represented in the goal model. Such contextual
preferences are used as criteria to evaluate alternative solutions that satisfy
the requirements variability problem. We utilise a state-of-the-art reasoning
implementation from the Answer Set Programming domain to automate the
derivation and evaluation of solutions that fulfill the goals and satisfy the
contextual preferences. Our approach will support systems analysts in their
decisions upon alternative design solutions that define subsequent system
implementations.
