A method and system for evolving XML-schema-based data to conform to an evolved XML schema is disclosed. Based on an existing XML schema and an instance document that is based on the existing XML schema, an XML-schema-independent form of the instance document is generated. Based on a set of specified transformations and the XML-schema-independent form of the instance document, an evolved instance document is generated. The evolved instance document conforms to an evolved XML schema that incorporates changes to the existing XML schema. Techniques described herein are flexible enough to accommodate a wide variety of evolutions to XML schemas.