When designing executable enterprise processes, the alignment between business and technical requirements is still one of the central problems. Process specifications obtained from the pure business perspective commonly cannot be executed "as-is" due to constraints of information systems given in the form of existing software services. In this paper we introduce several concepts targeted towards aligning business processes and service-based systems. The notion of realization levels is introduced to discern the level of business conformance. Furthermore, a model of system constraints is introduced to guide the developer to process realizations with high business conformance. By the combined use of the concepts, structured development and evolution of process realizations is enabled by continuous tracking of the alignment between business and the supporting technology.