The power of a service-oriented architecture (SOA) is in its ability to enable business agility through business process integration and reuse. SoaML (Service-Oriented Architecture Modeling Language) is an Object Management Group (OMG) standard that is intended to help realize the potential of SOA.
This article describes the business goals and objectives and the business processes implemented to meet those objectives, and then explains how to use the processes to identify business-relevant services necessary to fulfill the requirements that they represent.
The service architecture can realize use cases that capture information about the high-level functional and nonfunctional requirements for the business process from the perspectives of the key external stakeholders or actors. These use cases can be viewed in use case diagrams in Rational Requirements Composer or Rational Software Architect. This maintains the link between the service requirements contract, business processes, the business use case, and the business goals and objectives.
Whether you use business capabilities or service architectures, or both, to identify candidate services is a matter of personal preference. Business capability modeling is a straightforward way to decompose a business into competencies identifying the business capabilities and operations, and the relationships between capabilities needed to meet business objectives. Services architecture modeling provides a more formal way of specifying the participants and contracts governing their interactions. Both approaches can be used together. Use the approach most comfortable for you.
Read the full article on http://www.ibm.com/developerworks/rational/library/09/modelingwithsoaml-1/