Dealing with imprecise quality factors in software design

During the design of a software system impreciseness can manifest itself in for instance the requirements or performance estimations. While it is common to eliminate the impreciseness by information that can not be justified, it is better to model the impreciseness since it is the most accurate description that is available at the current point in time. In this paper we present an approach, which allows the explicit specification of quality estimations and quality requirements including the imprecise nature. In this approach the impreciseness is modeled and addressed using representations from probability theory and fuzzy set theory.