Don't base your web service data versioning strategy on a data validation strategy. Rather, base it on business needs.
Don't base your versioning strategy on an XML validation strategy, such as maintaining backward compatible XML Schemas. It's the data that the web service makes available to its consumers that matters, not how the schema is designed. Your web service may have a business need to create a new version in which new elements are added, old elements are deleted, and elements are rearranged ... none of these changes would be possible if your versioning strategy were constrained by some XML validation strategy such as trying to maintain backward compatible XML Schemas. The only thing that matters is the XML instance documents that the web service makes available to its consumers. The design of the XML Schema that the instance documents conform to is irrelevant.
Last Updated: January 6, 2008