"A reference architecture is a description of how to build a class of artifacts. An architecture describes how to build a particular artifact. The appropriate way to write the description for a reference architecture depends on the particular artifact. For example, you could describe the properties of the artifact. Another way is to write a set of steps (e.g., a recipe) for building the artifact. You could decompose the artifact to an appropriate number of components and subcomponents.
The SOA reference architecture (RA) provides a bridge between the concepts and vocabulary defined by the SOA Reference model and the implementation of a SOA. The SOA reference architecture models the abstract architectural elements for a SOA independent of the technologies, protocols, and products that are used to implement a SOA. Some sections of the RA will use common abstracted elements derived from several standards."