Digital systems can be specified conveniently at the system level by a set of requirements the target system should meet. The problem about this kind of specification is that there is no algorithmic way to gain an efficient system architecture fulfilling these requirements in the general case. This paper deals with the question of if restricting the design task to a single domain of systems, e.g. all RISC processors, instead of covering all digital systems can aid in solving this problem. We present an object-oriented approach for the description of a whole domain of digital systems and demonstrate how an abstract system specification can be transformed into a description of the target system in VHDL. Based on this approach we discuss the factors that influence the existence and complexity of an algorithm to derive an efficient implementation from an abstract system specification.