Proceedings

Abstract

Active XML vocabularies change over time, undergoing the inevitable evolution called versioning. Versioning means adding, deleting, or changing the elements, element content, number of occurrences, attributes, or attribute values described by an XML schema. Approaches to versioning fall into several classes, including compatible, backwards-compatible, forwards-compatible, and strategy-what-strategy. Specific rules enable the successful use of these strategies, such as the "must ignore unknowns" rule, the "must understand models" rule, and prescriptions for the use of version identifiers. Basic versioning concepts and vocabulary will be illustrated using a set-based model for determining compatibility.