Systems and methods are disclosed that facilitate formally describing structured documents and complex validation rules associated therewith using value-added XSD schemas (VAXs). Native XSDs can be utilized and annotated to generate VAXs that represent both the structure of a document and the complex validation rules used to validate the documents. VAXs can be annotated with declarative validation rules that can be assessed at run time to facilitate document validation. Additionally, VAXs can be annotated with validation handlers that comprise a predefined library of validation routines that can be called at run time to facilitate document validation.