The type xs:IDREFS represents a whitespace-separated list of one or more xs:IDREF values. In Example B-1, the refs attribute of secRef is assumed to be of type xs:IDREFS. The first refs attribute contains only one xs:IDREF (context), while the second contains two xs:IDREF values (context and language).

Because xs:IDREF is derived by restriction from xs:string, a value of type xs:IDREFS can be treated like a sequence of xs:string values.