XML in a Nutshell, 3rd Edition

Applying Templates with xsl:apply-templates

By default, an XSLT processor reads the input XML document from top to bottom, starting at the root of the document and working its way down using preorder traversal. Template rules are activated in the order in which they match elements encountered during this traversal. This means a template rule for a parent will be activated before template rules matching the parent’s children.

However, one of the things a template can do is change the order of traversal. That is, it can specify which element(s) should be processed next. It can specify that an element(s) should be processed in the middle of processing another element. It can even prevent particular elements from being processed. In fact, Examples Example 8-4 through Example 8-6 all implicitly prevent the child elements of each person element from being processed. Instead, they provided their own instructions about what the XSLT processor was and was not to do with those children.

The xsl:apply-templates element makes the processing order explicit. Its select attribute contains an XPath expression telling the XSLT processor which nodes to process at that point in the output tree.

For example, suppose you wanted to list the names of the people in the input document; however, you want to put the last names first, regardless of the order in which they occur in the input document, and you don’t want to output the professions or hobbies. First you need a name template that looks like this: ...