xlink:role Role of the Link
OPTIONAL on many elements; click for list and usage
<abbrev>, <award-desc>, <award-group>, <award-id>, <award-name>, <bio>, <chem-struct>, <collab>, <conference>, <content-version>, <contrib>, <custom-meta>, <element-citation>, <email>, <ext-link>, <extended-by>, <funding-source>, <funding-statement>, <graphic>, <inline-graphic>, <inline-media>, <inline-supplementary-material>, <institution>, <issue-id>, <license>, <long-desc>, <media>, <mixed-citation>, <named-content>, <product>, <pub-id>, <related-article>, <related-object>, <resource-name>, <restricted-by>, <self-uri>, <supplementary-material>, <support-source>, <uri>, <volume-id>
|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.|
URI reference to a site that explains the purpose of an external link
... <ext-link ext-link-type="uri" xlink:type="simple" xlink:role="http://www.mulberrytech.com/walkthewalk.html" xlink:title="XML-based slideshow application" xlink:actuate="onRequest" xlink:show="new" xlink:href="http://www.mulberrytech.com/slideshow/index.html"> Mulberry Slideshow XML</ext-link> ...