Extended links generally point to more than one target and from more than one source. Both sources and targets are called by the more generic word resource.
Resources are divided into remote resources and local resources.
A local resource is actually contained
inside the extended link element. It is enclosed in element of
arbitrary type that has an
xlink:type attribute with the value
resource.
A remote resource exists outside the extended link element, very possibly in
another document. The extended link element contains locator child elements that
point to the remote resource. These are elements with any name that have an
xlink:type attribute with the value locator.
Each locator element has an
xlink:href attribute whose value is
a URI locating the remote resource.