Since an MML instance consists of at least one module, version control in module units becomes necessary. With MML, including CLAIM, the version of the utilized module is indicated by the ending decimal number in the URI of the module namespaces declaration. Thus, in the namespaces declaration below, the version of the appointment request module is 2.1.
xmlns:claim ="http://www.medxml.net/claim/claimModule/2.1"