This part of ISO 13209 specifies a standardized, tester-independent, XML-based data exchange format for the documentation and formal description of diagnostic test sequences. The format serves to support the requirements of transferring diagnostic-test-sequence logic between electronic system suppliers, vehicle maufacturers and service dealerships/repair shops. This part of ISO 13209 provides an introduction to the rationale behind ISO 13209. It gives an overview of the document set and structure along with the use case definitions and a common set of resources (definitions, references) for use by all subsequent parts.