XLink is a web standard for creating hyperlinks to navigate an XML document.

XLink (XML Linking Language) is a web standard for creating hyperlinks to navigate an XML document.
XLink defines a set of attributes that may be added to elements of other XML namespaces.
XLink provides two kinds of hyperlinking for use in XML documents. Simple links connect only two resources, similar to HTML links. Extended links can link an arbitrary number of resources.

Simple links:

A simple link creates a unidirectional hyperlink from one element to another via a URI. Example:

<?xml version="1.0"?>
<document xmlns="http://example.org/xmlns/2002/document" xmlns:xlink="http://www.w3.org/1999/xlink">
  <heading id="someHeading">Some Document</heading>
  <para>Here is <anchor xlink:type="simple" xlink:href="#someHeading">a link</anchor> to the header.</para>
  <para>It is an anchor that points to the element with the id "someHeading" on the current page.</para>
</document>

Extended links:

Extended links allow multiple resources, either remote or local, to be connected by multiple arcs. An arc is information about the origin, destination and behavior of a link between two resources. The origin and destination resources are defined by labels. By using one or more arcs, an extended link can achieve specific sets of connections between multiple resources.

Useful references: