XML in a Nutshell, 3rd Edition

Attribute Value Templates

It’s easy to include known attribute values in the output document as the literal content of a literal result element. For example, this template rule wraps each input person element in an HTML span element that has a class attribute with the value person:

<xsl:template match="person">
  <span class="person"><xsl:apply-templates/></span>
</xsl:template>

However, it’s trickier if the value of the attribute is not known when the stylesheet is written, but instead must be read from the input document. The solution is to use an attribute value template. An attribute value template is an XPath expression enclosed in curly braces that’s placed in the attribute value in the stylesheet. When the processor outputs that attribute, it replaces the attribute value template with its value. For example, suppose you want to write a name template that changes the input name elements to empty elements with first, initial, and last attributes like this:

<name first="Richard" initial="P" last="Feynman"/>

This template accomplishes that task:

<xsl:template match="name">
  <name first="{first_name}"
        initial="{middle_initial}"
        last="{last_name}" />
</xsl:template>

The value of the first attribute in the stylesheet is replaced by the value of the first_name element from the input document. The value of the initial attribute is replaced by the value of the middle_initial element from the input document, the value of the last attribute is replaced by the value of the last_name element ...