Read XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition Online
Authors: Michael Kay
If the value of an attribute of a literal result element contains curly braces (
{
and
}
), then it is treated as an
attribute value template
(discussed further in the next section). The text between the curly braces is treated as an XPath expression, and is evaluated as a string; the attribute written to the result tree contains this string in place of the expression. For example, suppose we apply the following template to the
books.xml
file used earlier:
Because the
position()
function takes the values 1, 2, 3, and 4, as we move through the set of books, the output will take the following form:
It is also possible to generate attributes for a literal result element by two other mechanisms:
The reason for this rule is to allow the XSLT processor to avoid building the result tree in memory. Many processors will serialize XML syntax directly to an output file as the nodes are generated, and the rule that attributes must be generated before child elements or text nodes ensures that this is possible. Technically, it's not the order in which the instructions are evaluated that matters (that's up to the implementation); rather, the rule is that attribute nodes in the result of evaluating a sequence constructor must appear earlier in the sequence than nodes to be used as children.
Attributes are added to the generated element node in a defined order: firstly, attributes incorporated using
xsl:use-attribute-sets
, then attributes present on the literal result element itself, and finally attributes added using
Namespaces for a Literal Result Element
The namespace nodes of a literal result element are also copied to the result sequence of the sequence constructor. This is often the source of some confusion. The literal result element in the stylesheet will have a namespace node for every namespace declaration that is in scope: that is, every
xmlns
or
xmlns:*
attribute on the literal result element itself, or on any of its ancestor elements in the stylesheet. The only exception is that the attribute
xmlns = “”
does not act as a namespace declaration, rather it cancels any earlier declaration for the default namespace.