XLinks can do everything HTML links can do and quite a bit more, but they aren't supported by current applications.
XLink elements of all types are placed in the
http://www.w3.org/1999/xlink namespace, normally with
the xlink prefix. However, the URI is likely to
change in future revisions to XLink.
Simple links behave much like HTML links, but they are not
restricted to a single <A> tag.
Linking elements are identified by xlink:type
attributes.
Simple link elements are identified by
xlink:type attributes with the value simple.
Linking elements can describe the resource they're linking to
with xlink:title and xlink:role attributes.
Linking elements can use the xlink:show attribute to
tell the application how the content should be displayed when
the link is activated, for example, by opening a new window.
Linking elements can use the xlink:actuate attribute to
tell the application whether the link should be traversed
without a specific user request.
Extended link elements are identified by
xlink:type attributes with the value extended.
Extended links can contain multiple locators, resources, and arcs. Currently, it's left to the application to decide how to choose between different alternatives.
Resource elements are identified by xlink:type
attributes with the value resource.
Locator elements are identified by xlink:type
attributes with the value locator.
A locator element has an
xlink:href attribute whose value is the URI of the
resource it locates.
Arc elements are identified by xlink:type
attributes with the value arc.
Arc elements have xlink:from and xlink:to
attributes of IDREF type that identify the
resources they connect by their roles.
Arc elements may have xlink:show and
xlink:actuate attributes to determine when and how
traversal of the link occurs.
An out-of-line link is a link that does not contain any local resources.
A linkbase is a document containing multiple out-of-line, extended link elements.
A linkbase is found when a document with an extended link with the role xlink:external-linkset is read.