Resource-type element

<!ELEMENT gpa ANY>
<!ATTLIST gpa
  xlink:type      (resource)      #FIXED "resource"
  xlink:role      CDATA           #FIXED "http://www.example.com/linkprops/gpa"
  xlink:title     CDATA           #IMPLIED
  xlink:label     NMTOKEN         #IMPLIED>

<gpa xlink:label="PatJonesGPA">3.5</gpa>