Balisage Paper: Forward compatibility using XML transform-as-needed (XTAN)
Sandro Hawke has been a member of the W3C Semantic Web Activity technical staff, at MIT, since 2000, and served as a software developer for what has become MIT's Decentralized Information Group. These days he enjoys programming in Prolog and Python. He is currently the staff contact for the Rule Interchange Format (RIF) Working Group and the OWL (Web Ontology Language) Working Group.
It is often desirable to design vocabularies for forward compatibility, that is, to design them in such a way that domain-specific applications that use them can be adapted to changes in them at minimal (and predictable) costs. XTAN is a vocabulary for annotating XML Schemas to indicate how documents that use certain vocabulary extensions can be transformed by an XTAN preprocessor into documents that do not use those features. The transformation may have specific impacts, including losses of fitness for specific uses in specific domains. By using XTAN, systems can provide forward compatibility: a document that uses features not specified in version n of its vocabulary can be transformed automatically (with some impact) into a version n document. XTAN is being developed to meet the needs of the W3C Rule Interchange Format (RIF) Working Group, but the design is general.