title: XML Validation: XSD or Schematron?
body: <p>I need to tighten validation on a moderately complex schema (SAML Metadata) comprising approx. 10 XSD files giving 1000 lines of schema definition. The validation should primarily require optional elements and attributes, restrict node and attribute contents to certain values, issue warnings on recommended or deprecated elements and attributes, and refuse anything that is not part of the schema, including stuff in extension elements of the original schema.
  What is the best approach for this? Plain XSD, XSD + assertion, Schematron, or using some language and parse the document?</p>