XSLT, 2nd Edition

Whitespace Basics

Before we begin, it’s worth defining the four characters that the XML spec defines as whitespace:

• The tab character (	)

• The newline character (
)

• The carriage return character (
)

• The space character ( )

We’ll use this modified version of our car list to illustrate how XML parsers and XSLT processors work with whitespace:

<?xml version="1.0" encoding="utf-8"?>
<!-- carlist_whitespace.xml -->
<cars>
  <manufacturer name="          Chevrolet

">
    <car>Cavalier</car>
    <car>Corvette</car>
    <car>Impala</car>
    <car>Monte



Carlo</car>
  </manufacturer>
</cars>

From an XML parser’s perspective, there are a number of whitespace-only nodes (nodes that contain only whitespace characters) in this document. The <cars> element contains a whitespace-only node with the newline character and the tab or spaces before the <manufacturer> tag, the node for the <manufacturer> element, and a whitespace-only node with the newline character after the </manufacturer> tag. Similarly, the <manufacturer> element contains whitespace-only nodes between the various <car> elements.

The XML parser doesn’t remove any whitespace-only nodes, so we can always use them in our stylesheets. Put another way, the data model used by the XSLT processor contains the whitespace-only nodes from the XML source. The one exception to this is in an XSLT 2.0 processor that validates the XML source against a schema. If the schema indicates that an element can only contain other elements, any whitespace-only nodes contained ...