XML Schema - odkaz na sdefinici schématu

<book isbn="0836217462"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:noNamespaceSchemaLocation="file:library.xsd"> <!-- mezera !!! -->

<book isbn="0836217462"
      xmlns="http://example.org/ns/books/"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation=
           "http://example.org/ns/books/ file:library.xsd"> <!-- mezera !!! -->