Define the Request/Response Schemas

Once the business object has been identified, we have to expose it as a pair of request/response XML schemas. The XML schemas are the foundation of the product APIs. They define both the structure of the documents that are exchanged between a service requester and the system and the internal mapping between the XML documents and the implementation of the business object in the system

Every service is defined by a pair of XML Schemas: the request and response schemas. The schemas contain additional information that maps the XML elements to the service. The request/response schemas are usually different, but in some cases may be the same schema.