The ODM has been designed to provide a standard format for interchange and archive of clinical study data and metadata. Although the model has proven to be usable with a wide variety of clinical data applications, it is sometimes the case that individual clinical data systems store information that cannot be expressed in the ODM model. To encourage these systems to adopt the use of the ODM standard for interchange and archive and to improve interoperability of clinical research applications, the use of the ODM vendor extensions is recommended.

Requirements for extensions to the ODM model are:

1. Vendors must supply an XML or JSON Schema fully describing their extended ODM format.
2. Extended ODM files should reference the proper extension schema.
3. The extension may add new elements and attributes, but may not render any standard ODM elements or attributes obsolete. Extensions cannot be used for information that is normally expressed using other ODM elements.
4. For extensions represented in XML, all new elements and attributes must use distinct XML namespaces to ensure that there are no naming conflicts with other extensions. Because JSON does not support namespaces, extensions represented in JSON must ensure no naming conflicts exist with the ODM standard as well as any other extensions involved in the targeted use cases.
5. Removing all extensions from an extended ODM file must result in a meaningful and accurate standard ODM file.
6. Implementers should be able to produce ODM files free of any extensions upon request.

Applications that use extended ODM files must also accept standard ODM files.