XML in a Nutshell, 3rd Edition

Unabbreviated Location Paths

Up until this point, we’ve been using what are called abbreviated location paths . These are easy to type, not usually verbose, and very familiar to most people. They’re also the kind of XPath expression that works best for XSLT match patterns. However, XPath also offers an unabbreviated syntax for location paths, which is more verbose but perhaps less cryptic and definitely more flexible than abbreviated location paths.

Every location step in a location path has two required parts, an axis and a node test, and one optional part, the predicates. The axis tells you which direction to travel from the context node to look for the next nodes. The node test tells you which nodes to include along that axis, and the predicates further reduce the nodes according to some expression.

In an abbreviated location path, the axis and the node test are combined, while in an unabbreviated location path, they’re separated by a double colon (::). For example, the abbreviated location path people/person/@id is composed of three location steps. The first step selects people element nodes along the child axis. The second step selects person element nodes along the child axis. The third step selects id attribute nodes along the attribute axis. When rewritten using the unabbreviated syntax, the same location path is child::people/child::person/attribute::id.

These full, unabbreviated location paths may be absolute if they start from the root node, just as abbreviated paths ...