Simple solution: <recordSchema> in the request is a simple string. It can contain either the short name of a record schema (as mapped in Explain) or the full identifier. We could change the semantics to: It can contain one or more short names or identifiers. If more than one is supplied and the first is a 'wrapper' schema, then the second and subsequent should be returned within that wrapper. If the first is not a know wrapper schema then the server should treat it as a choice of any of the schemas. [currently an extension] eg: <recordSchema>mets dc rec</recordSchema> If the server doesn't support this, it will return a diagnostic saying: I don't support record schema "mets dc rec". If the server does support it, but doesn't support one of the individual schemas, it could return: I don't support record schema "rec" If it's a choice and the server doesn't support any of the schemas, it can return multiple diagnostics, one for each. Rob