Requirements can differ in their importance. As
such the priorities that stakeholders associate with requirements
may vary from stakeholder to stakeholder and from
one situation to the next. Differing priorities, in turn, imply
different design decisions for the end system. While elicitation
of requirements priorities is a well studied activity, though,
the modeling and reasoning side of prioritization has not
enjoyed equal attention. In this paper, we address this by
extending a traditional goal modeling notation to support the
representation of optional and preference requirements. In our
extension, optional goals are distinguished from mandatory
ones. Then, quantitative prioritizations of the former are
constructed and used as criteria for evaluating alternative
ways to achieve the latter. A state-of-the-art preference-based
planner is utilized to efficiently search for alternatives that best
satisfy the given preferences. This way, analysts can acquire
a better understanding of the impact of high-level stakeholder
preferences to low-level design decisions.