In-place XML schema evolution occurs by evaluating an existing XML schema in a database system to see if it is compatible with a new XML schema. To determine if the old schema is compatible with the new schema, a lock-step traversal is performed on the two schemas. Each instruction in the old schema...http://www.google.co.uk/patents/US7870163?utm_source=gb-gplus-sharePatent US7870163 - Implementation of backward compatible XML schema evolution in a relational database system
