Syntax and Semantics
- This section describes XPath 1.0.
The most important kind of expression in XPath is a location path. A location path consists of a sequence of location steps. Each location step has three components:
- an axis
- a node test
- zero or more predicates.
An XPath expression is evaluated with respect to a context node. An Axis Specifier such as 'child' or 'descendant' specifies the direction to navigate from the context node. The node test and the predicate are used to filter the nodes specified by the axis specifier: For example the node test 'A' requires that all nodes navigated to must have label 'A'. A predicate can be used to specify that the selected nodes have certain properties, which are specified by XPath expressions themselves.
The XPath syntax comes in two flavours: the abbreviated syntax, is more compact and allows XPaths to be written and read easily using intuitive and, in many cases, familiar characters and constructs. The full syntax is more verbose, but allows for more options to be specified, and is more descriptive if read carefully.
Read more about this topic: XPath
Famous quotes containing the words syntax and:
“Syntax and vocabulary are overwhelming constraints—the rules that run us. Language is using us to talk—we think we’re using the language, but language is doing the thinking, we’re its slavish agents.”
—Harry Mathews (b. 1930)