xlink:href

Href (Linking Mechanism)

An address or identifier that permits an XLink application to find a remote resource, for example, a URI (such as a URL or filename) that links to an online site associated with the author or the online definition of a term.

Remarks

As specified in XML Linking Language (XLink) Version 1.0 the value of an @xlink:href must be a valid URI.
Of the many linking attributes that may be used, @xlink:href is the most important, since it provides the link. The attribute is required for those elements which must link, and it is optional on other elements only in the sense that an element need not link. If an element links, this attribute is required.

Used on Elements: <graphic>, <inline-graphic>, <media>

ValueMeaningBehavior
Text, numbers, or special charactersA pointer (a URL) to a resource.Can be used to make this element a live link to a related site
Restriction@xlink:href is required; it must be provided if the element is used.

Used on these Elements:

ValueMeaningBehavior
Text, numbers, or special charactersA pointer (a URL) to a resource.Can be used to make this element a live link to a related site
Restriction@xlink:href is an optional attribute; there is no default.

Example 1

Provide navigation for an external link (element <ext-link>) in text. The content of this <ext-link> also displays the linking URI, but the content could have displayed text such as a “Breastfeeding Manual”.
 ...
<ext-link ext-link-type="url" xlink:href="www.ncemch.org/pubs/PDFs/
breastfeedingTIB.pdf">http://www.ncemch.org/pubs/PDFs/
breastfeedingTIB.pdf</ext-link>
... 

Example 2

Link to a spreadsheet:
 ...
<supplementary-material id="S1" xmlns:xlink="http://www.w3.org/1999/xlink"
xlink:title="local_file" xlink:href="pbio-0020328-t002.xls"
mimetype="application/vnd.ms-excel">
...</supplementary-material>
...