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B.6. The XPath Context

The context in an XPath expression consists of several things:

Context node
The node currently being evaluated.

Context position
A nonzero positive integer that indicates the position of the context node within the set of context nodes.

Context size
A nonzero positive integer that indicates the number of nodes in the current context.

Variable bindings
A set of variables that are in scope for the current context. Each one is represented by a variable name and an object that represents its value. The object might be one of the four XPath datatypes, some additional type defined by an extension, or some other entity.

A set of functions visible to the current context. Each function is represented by a mapping between a function name and the actual code to be invoked. Each function takes zero or more arguments and returns a single result. XPath defines a number of core functions that are always available; XSLT defines additional functions that go beyond those defined in the XPath specification.

Namespace declarations
The set of namespace declarations visible to the current context. Each one consists of a namespace prefix and the URI with which it is associated.

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