When building a Service Oriented Architecture, a Canonical Schema is important.
Further details in this article from 2004.
Not only do disparate services have different views of an entity, they may also have their own schematic representation of their views. In order to achieve a single unified view of an entity, it is imperative for the EA service to harmonize the schematic differences between different services. To do this, the EA service should first know how each service represents an entity. Additionally, the EA service should define a holistic view of the entity by logically consolidating the various views. Equally important is for the EA service to discover a way to represent the transformation between a service's view of an entity and the holistic view. The following figure shows the customer information represented in more than one service.