The five parts of the ISO EN 13606 standard define a means by which health-care records can be exchanged between computer systems. Starting within the European standardisation process, it has now become internationally ratified in ISO. However, ISO standards do not require that a reference implementation be provided, and in order for ISO EN 13606 to deliver the expected benefits, it must be provided not as a document, but as an operational system that is not vendor specific. This article describes the evolution of an Extensible Markup Language (XML) Schema through three iterations, each of which emphasised one particular approach to delivering an executable equivalent to the printed standard. Developing these operational versions and incorporating feedback from users of these demonstrated where implementation compromises were needed and exposed defects in the standard. These are discussed herein. They may require a future technical revision to ISO EN 13606 to resolve the issues identified.