One of the major aims of ongoing research at Erasmus University Rotterdam is to design and develop an expert system that will be able to analyze the strength of an enterprise and to advise about the strategies this enterprise must follow. A part of this research concerns the design of an object-oriented (OO) model of an enterprise and its environment. Such a model can be used as framework for expert system design and development. In this paper such an OO model is presented and related issues are discussed such as which object classes will have to be selected and how they are interrelated. For this OO model design Rumbaugh's Object Modeling Technique has been used. Some attention is paid to the implementation of this model in Aion DS, an OO knowledge representation tool.