Extension functions

There are a number of functions that the XPointer standard defines for use in expressions. These are:

location-set start-point(location-set)
location-set end-point(location-set)
location-set range(location-set)
location-set range-to(location-set)
location-set range-inside(location-set)
location-set string-range(location-set, string, number?,
                          number?)

location-set here()
location-set origin()

xmlns(prefix=namespaceURL)

The first five deal with points and ranges, allowing groups of elements or characters to be treated as a single target object. The next two deal with alternative, relative context locations for the start of the path. The final function is used to manage namespace mappings in expressions, and deals with multiple mappings to the same prefix, as well as unknown prefix usage in the document. They are all described in more detail in following sections.