Web services are often employed to create wide distributed evolvable applications from existing components that constitute a service-based software system. Service- Oriented Architectures promote loose coupling, services distribution, dynamicity and agility. As services involved in a SOA are remote and autonomous services, the SOA designer does not control them and unpredictable behaviour can occur. Services orchestration is a key issue in order to fit expectations and reach objectives. Thus, service-oriented architectures have to be designed and deployed with rigor in order to be plainly useful and quality aware. Orchestration languages (BPEL4WS, BPML, etc.) fail in some points due to the lack of formalization and expressiveness, particularly when addressing service-based architecture evolution. This paper presents Diapason, an engineering approach for fully and formally designing service-based architectures, deploying them on the Internet, executing them according to the design and dynamically evolving them taking into account business changes and modifications.