“Defining Message Formats” is the title of a message posted on the Service Oriented Architecture mailing list [1] which attracted a lot of attention. The post summarizes the dilemma faced by solution architects when they have to define a service interface: 1. Base the internal message format on the external message standard (MISMO for this industry). This message set is bloated, but is mature, supports most areas of the business, and is extensible for attributes specific to this company and its processes. 2. Create an XML-based message set based on the company's enterprise data model, which the company has invested a great amount of money into, and includes a very high percentage of all attributes needed in the business. In a nutshell, we've generated an XML Schema from ER Studio, and will tinker with that construct types that define the payloads for messages. 3. Use MISMO mainly for its entity definitions, but simplify the structure to improve usability. We benefit from the