xlink:role Role of the Link

A URI reference pointing to some resource that describes the role or function of a link.
OPTIONAL on many elements; click for list and usage
Value Meaning
Text, numbers, or special characters The URI of a resource that describes the role, reason, or rationale for the link.
Restriction @xlink:role is an optional attribute; there is no default.
Tagged Sample

URI reference explaining the purpose of an external link (in this instance, to XML coding)

<ext-link ext-link-type="url" xlink:type="simple"
  xlink:title="XML-based slideshow application"
  xlink:actuate="onRequest" xlink:show="new"
 Mulberry Slideshow XML</ext-link>