The transformation of requirements specification into an architectural design has been a crucial endeavor for the information systems analysis and design community, with ever-new challenges to tackle. Despite the wide and diverse existing proposals, the lack of a common structure and use of different strategies makes it close to impossible to analyze or compare these approaches. Therefore, the use of model-based methods benefits from a detailed specification in order to support their analysis and evolution, also in comparison to other approaches. Following work on the derivation of a logical architecture from business-process use-cases requirements in a service-oriented approach, the authors propose a detailed specification, within a SPEM approach, of a transformation method, which they further analyze and refurbish in order to meet current and future challenges.