A child sequence is a shortcut for XPointers that consist of nothing but a series of child relative location steps counting down from the root node, each of which selects a particular child by position only.
The shortcut is to use only the position number and the slashes that separate individual elements from each other, like this:
http://www.theharolds.com/genealogy.xml#/1/4
/1/4 is a child sequence that says to select the
fourth child element of the first child element of the root.
Child sequences may include an initial ID. In that case the
counting begins from the element with that ID rather than from
the root. For example, John P. Muller's PERSON element has an ID
attribute with the value p4. Consequently the XPointer p4/1
points to his NAME element and p4/2 points to his SPOUSE
element.
Each child sequence always points to a single element. You cannot use child sequences with any other relative location steps. You cannot use them to select elements of a particular type. You cannot use them to select attribute or strings. You can only use them to select a single element by its relative location in the tree.