A method and apparatus for designing an optimal IS architecture of a business entity is disclosed. In different levels of abstraction, a business operations model, an applications model, a physical requirements model and technical infrastructure model are produced. The models in a stepwise manner generate an IS architecture meeting desired performance criteria of the business entity. An optimizer evaluates, in a numerical manner, implementations of the IS architecture and design alternatives such that an optimal IS architecture is determined. Subsequent continual refinement of the IS architecture is achieved by remodeling the physical requirements and the technical infrastructure, and by evaluating through the optimizer the then produced IS architecture.