XLink and XPointer

XLink

XLink (XML Linking Language) provides a framework for creating links between XML resources. It supports simple links as well as more complex linking relationships.

It uses attributes such as xlink:href to identify a linked resource.

<book xmlns:xlink="http://www.w3.org/1999/xlink"
      xlink:type="simple"
      xlink:href="chapter2.xml">
  Chapter 2
</book>

XPointer

XPointer (XML Pointer Language) extends the idea of URI references by allowing a link to identify a particular part or fragment of an XML document rather than only the whole document.

Difference

XLink	XPointer
Defines linking relationships	Identifies locations/fragments in XML resources
Describes how resources are linked	Describes where a link points within a resource

In short: XLink handles XML linking; XPointer provides fine-grained addressing within XML content.