4 Expressions
Expressions
XSLT uses the expression language defined by XPath [XPATH]. Expressions are used in XSLT for a variety of purposes
including:
selecting nodes for processing;
specifying conditions for different ways of processing a node;
generating text to be inserted in the result tree.
An
expression must match the XPath production Expr.
Expressions occur as the value of certain attributes on
XSLT-defined elements and within curly braces in Attribute Value Templates.
In XSLT, an outermost expression (i.e. an expression that is not
part of another expression) gets its context as follows:
-
the context node comes from the Current Node
-
the context position comes from the position of the Current Node in the Current Node List; the first
position is 1
-
the context size comes from the size of the Current Node List
-
the variable bindings are the bindings in scope on the
element which has the attribute in which the expression occurs (see
[Variables and Parameters])
-
the set of namespace declarations are those in scope on the
element which has the attribute in which the expression occurs;
this includes the implicit declaration of the prefix xml
required by the the XML Namespaces Recommendation [XMLNAMES];
the default
namespace (as declared by xmlns) is not part of this
set
-
the function library consists of the core function library
together with the additional functions defined in [Additional Functions] and extension functions as described in [Extensions]; it is an error for an expression to include a call
to any other function
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