XSLT, 2nd Edition

[2.0] New Grouping Syntax in XSLT 2.0

In 2001, the XSL Working Group released a document entitled “XSLT Requirements Version 2.0.” More than half of the document came under the heading “Must Simplify Grouping.” (I can’t imagine how the group would have met a requirement named “Must Make Grouping More Complicated and Confusing.”) We’ll take a look at those changes in this section.

XSLT 2.0’s grouping functions are built around the <xsl:for-each-group> element. Within this element, we’ll use the new XSLT functions current-group() and current-grouping-key() to work with the data we’re grouping. There are four mutually exclusive attributes for the <xsl:for-each-group> element, each of which performs a different style of grouping:

group-by

This is the most common type of grouping. We use an XPath expression to define what identifies a group (all of the <address> elements that have the same <zip> code, for example), so we can then iterate through each group.

group-adjacent

This approach is useful when you want to build a group containing all the adjacent nodes that match an XPath expression. As an example, we’ll take all the adjacent <p> elements in a document, convert each one to an <li> element, and put <ul> and </ul> tags around the entire group.

group-starting-with

The group-starting-with attribute defines an XPath expression that identifies the start of a group. Once a group starts, every element is added to the group until the start of another group is found. group-starting-with and