XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition

Chapter 7. XPath Fundamentals

This chapter defines some fundamental features of the XPath language. The first half of the chapter describes the basic syntactic and lexical conventions of the language, and the second half describes the important notion of context: this establishes the way in which XPath expressions interact with the environment in which they are used, which for our purposes primarily means the containing XSLT stylesheet.

The complete grammar of the language is summarized in Appendix A, and for convenience I have split the constructs of the language across five chapters, as follows:

Chapter	Scope
7	Notation used for describing the grammar Overall structure of the language Lexical rules (including comments and whitespace handling) Literals Variable references Parenthesized subexpressions Context item expression «.» Function calls Conditional expressions: «if»
8	Arithmetic operators: «+», «−», ... Value comparison operators: «eq», «lt», ... General comparison operators: «=», «<», ... Node identity and ordering operators: «is», «<<», «>>» Boolean operators: «and», «or»
9	Path expressions: «/», «//» Steps and axes Union, intersect, and except operators
10	Sequence concatenation operator: «,» Numeric range operator: «to» Filter expressions «a[b]» Mapping expressions: «for» Quantified expressions: «some» and «every»
11	SequenceType production «instance of» «castable as» «cast as» «treat as»

As with other programming languages, the syntax is defined in a set of production rules. Each ...