xsl:for-each-group

The xsl:for-each-group element selects a sequence of nodes and/or atomic values and organizes them into subsets called groups. There are four possible ways of defining the grouping:

• group-by: This groups together all items having the same value for a grouping key. The grouping key may have multiple values (a sequence of values) in which case the item is added to more than one group.

• group-adjacent: This groups together all items having the same value for a grouping key, provided that they are also adjacent in the input sequence. This is useful when you need to wrap a new element around a sequence of related elements in the source documents, for example a consecutive sequence of <bullet> elements. In this case the grouping key must be single-valued.

• group-starting-with: This processes the items in the supplied sequence in turn, starting a new group whenever one of the items matches a specified pattern. This is useful, for example, when matching an <h2> element and its following <p> elements.

• group-ending-with: This processes the items in the supplied sequence in turn, closing the current group whenever one of the items matches a specified pattern. This is useful when matching a sequence of items in which the last item in the group carries some distinguishing attribute such as continued="no".

Saxon implements the xsl:for-each-group instruction in full. For examples of using the instruction, see the XSLT 2.0 specification.

In XSLT 3.0, the capabilities of the xsl:for-each-group instruction are extended by virtue of the fact that the pattern used in group-starting-with or group-ending-with can now match atomic values as well as nodes.