XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition (418 page)

Rooted Path Expressions

I will use the term
rooted path expression
to mean a path expression that starts with
/
or
//
. In XPath 1.0 these were called absolute path expressions; there is no specific name for them in the 2.0 specification, but I have avoided the word
absolute
because it conceals the fact that the value of these expressions does, in fact, depend on the context node.

The full syntax for path expressions is shown below. We already saw the production
RelativePathExpr
at the beginning of this chapter.

Syntax

Expression	Syntax
PathExpr	( / RelativePathExpr?) | ( // RelativePathExpr) | RelativePathExpr
RelativePathExpr	StepExpr ( ( / | // ) StepExpr )*

This production indicates that there are four forms a path expression can take, namely:

• /
  (a
  root expression
  , already discussed on page 623)
  
• /
  RelativePathExpr
  (the subject of this section)
  
• //
  RelativePathExpr
  (discussed later on page 626)
  
• RelativePathExpr
  (a sequence of steps separated by the binary
  /
  operator, which we examined at the start of this chapter)