An abstract view of SOA depicts it as a partially layered architecture of composite services that align with business processes. Figure 3 depicts a representation of this type of architecture.

The relationship between services and components is that enterprise-scale components (large-grained enterprise or business line components) realize the services and are responsible for providing their functionality and maintaining their quality of service. Business process flows can be supported by a choreography of these exposed services into composite applications. An integration architecture supports the routing, mediation, and translation of these services, components, and flows using an Enterprise Service Bus (ESB). The deployed services must be monitored and managed for quality of service and adherence to non-functional requirements.

For each of these layers, you must make design and architectural decisions. Therefore, to help document your SOA, you might want to create a document consisting of sections that correspond to each of the layers.

Here is a template for your SOA architecture document:

Layer 1: Operational systems layer. This consists of existing custom built applications, otherwise called legacy systems, including existing CRM and ERP packaged applications, and older object-oriented system implementations, as well as business intelligence applications. The composite layered architecture of an SOA can leverage existing systems and integrate them using service-oriented integration techniques.

Layer 2: Enterprise components layer. This is the layer of enterprise components that are responsible for realizing functionality and maintaining the QoS of the exposed services. These special components are a managed, governed set of enterprise assets that are funded at the enterprise or the business unit level. As enterprise-scale assets, they are responsible for ensuring conformance to SLAs through the application of architectural best practices. This layer typically uses container-based technologies such as application servers to implement the components, workload management, high-availability, and load balancing.