Athena is the ATLAS off-line software framework, based upon the GAUDI architecture from LHCb. As part of ATLAS' continuing efforts to enhance and customise the architecture to meet our needs, we have developed a data object description tool suite and service for Athena. The aim is to provide a set of tools to describe, manage, integrate and use the Event Data Model at a design level according to the concepts of the Athena framework (use of patterns, relationships, ...). Moreover, to ensure stability and reusability this must be fully independent from the implementation details. After an extensive investigation into the many options, we have developed a language grammar based upon a description language (IDL, ODL) to provide support for object integration in Athena. We have then developed a compiler front end based upon this language grammar, JavaCC, and a Java Reflection API-like interface. We have then used these tools to develop several compiler back ends which meet specific needs in ATLAS such as automatic generation of object converters, and data object scripting interfaces. We present here details of our work and experience to date on the Athena Definition Language and Athena Data Dictionary.