ISO/IEC 21838
ISO/IEC 21838 is a multi-part standard published by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) in 2001, which outlines requirements for top-level ontology development and describes several top-level ontologies that satisfy those requirements, including Basic Formal Ontology (BFO), Descriptive Ontology for Linguistic and Cognitive Engineering (DOLCE), and TUpper. ISO/IEC 21838 is intended to promote interoperability among lower level, domain-specific ontologies, and to foster coherent ontology design, for example, through the coordinated re-engineering of legacy ontologies which have been developed using heterogeneous top-level categories.