Although a considerable number of successful frameworks have been developed during the last decade, designing a high-quality framework is still a difficult task. Generally, it is assumed that the correct abstractions is very hard, and therefore a successful framework can only be developed through a number of iterative (software) development efforts. Accordingly, existing framework development practices span a considerable amount of refinement time, and it is worthwhile to shorten this effort. To this end, this paper aims at defining explicit models for the knowledge domains that are related to a framework. The absence of such models may be the main reason for the currently experienced extensive refinement effort. The applicability of the approach is illustrated by means of three pilot projects. We experienced that some aspects of domain knowledge could not be directly modeled in terms of object-oriented concepts. In this paper we describe our approach, the pilot projects, the experien...