The papers charts the development that have taken place in product-data exchange standards and specifications since 1987, particulary with reference to conformance testing. The lessons learned from existing specifications, and the work being undertaken in other areas (such as graphics and open-systems interconnection), are recognized, and are applied in the definition of the emerging international standard STEP. STEP Version 1.0 should be ready for ballot by July 1991; the paper explains the expected form and content of that version.