To understand SOA architectures, The Open Group SOA RA and OASIS SOA RA both provide an understanding of the different elements of SOA and considerations for enterprise and cross-ownership boundaries in SOA ecosystems from different viewpoints. The OASIS SOA RA is more abstract and focused on an SOA ecosystem viewpoint and the cross-organizational ownership boundaries that accompany it. It provides models that function as a checklist that can be used to evaluate architectures and SOA implementations.
The Open Group SOA RA is more focused on SOA initiatives in the enterprise; guiding architects to use and deploy SOA architectural building blocks and to evaluate the implications of architectural decisions. It provides a base RA for users to refine industry and organizational RAs and positioning products in an SOA context.
To understand your organizations service maturity, the OSIMM (referenced above) provides a service integration maturity model that describes the broadest scope of service use so that companies can understand what SOA features they are using, which ones they want to use, and an incremental roadmap to get there.
To understand how to model SOA, OMGs SOA modeling language (SoaML) provides a UML profile for modeling SOA artifacts (starting with OASIS SOA RM concepts) and services for your SOA as part of the transformation from a RA to your SOA solution architecture.