This dissertation proposes a new model for the representation of design processes based on the evolutionary aspect of this type of process. Also this work presents an innovative approach to object-oriented design processes and a new pragmatic view of the Design Problem Space (DPS) based on the design history. Furthermore, the principles underlying the model are derived from a working CAD system in furnace design developed during the present research work. The proposed model is structured in terms of a small number of object types which are capable of building an efficient and robust hierarchical tree. This tree incorporates all the requirements associated with the artefact from the conceptual stage up to the stage of the artefact complete specification. The proposed model is presented in the context of a complete design automation system and several working requirements are discussed, such as version control, alternative manipulation and history navigation. Moreover, a number of suggestions for future work is discussed and a selective literature for open questions are presented.