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178 CHAPTER 6 INTRODUCTION TO XSLT

Figure 6-3 shows how planets2.xmlappears in IE. Figure 6-3. The page planets2.xml showing a simple table of contents You can see a Quick reference section at the top of the page with links to each of the sections below.
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CHAPTER 6 INTRODUCTION TO XSLT 177 Using XSLT to generate the table of contents is useful because You can generate the table of contents from existing XHTML, and you don t need to use server-side logic to extract the information from a database or other data source. The table of contents always reflects the current page contents, and it updates when the current page changes; you ll see an example a little later in this section. You reduce server load because no server-side processing is required to generate the table of contents. You can see this example in the file planets2.xml. If you open the file, you ll notice that the first line refers to a stylesheet called planets2.xsl: The planets2.xsl stylesheet follows:

Visit NASA! | Tour the solar system

Quick reference

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Copyright Planetary Fun 2006.
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176 CHAPTER 6 INTRODUCTION TO XSLT WHICH TEMPLATE WILL BE APPLIED? In XSLT 1.0, has a priority attribute that allows you to specify which template to apply if several match a node. A higher priority indicates that the template should apply in preference to others. If the template doesn t specify a priority, it s quite complicated to determine the order in which templates apply. Section 5.5 of the XSLT specification describes the complete process (http://www.w3.org/ TR/xslt#conflict). In essence, the rules state that the XSLT processor should use the most specific of all matching templates. In this example, the identity template matches every node, including the element, but because you have a specific template, that takes precedence. You can use the following identity transformation lines to pass these tags through unchanged: The identity transformation template leaves everything in its original state. It matches every part of the source XML document that doesn t have its own style rule and passes it through unchanged. The identity transformation matches all nodes (node()) and attributes (@*) within the source document. When it finds a match, the rule uses to create an identical copy of the matching item. The tag processes the contents of the matched item without changing them. If this were the only template within an XSLT stylesheet, it would produce a document functionally the same as the source document. You can t use this template when the output document is substantially different from the input document. Normally, you d use it as you ve seen in this example to pass through the unchanged content along with another simple template. Each element or attribute in the source XML document can only be matched by one template, so you need to copy the element to the output document rather than relying on the identity template to do it for you. Because the template is more specific than the identity transformation template, that declaration takes precedence. Let s move on to another example, where I ll use XSLT to repeat content from the source document using a different layout. Creating a Table of Contents This example creates a table of contents showing the nearest planets to us in the solar system. It shows how to generate new content automatically from existing content. Without this approach, you would have to generate the list with server-side logic or by using JavaScript to manipulate the Document Object Model (DOM) and write out the contents.
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CHAPTER 6 INTRODUCTION TO XSLT 175 The first line of this code block tells the XSLT processor to match the element. The transformation applies to everything between the opening and closing tags. The stylesheet achieves this with the element, which specifies a template for the transformation. The next four lines show what to insert at the start of the template, before the contents from the original element. The stylesheet adds a paragraph with two links. The template doesn t transform the tag itself, so you have to include this tag at the start of the template. The transformation changes the starting tag to

Visit NASA! | Tour the solar system

This transformation includes a header with two links. Applying the Transformation The following line actually applies the transformation to the element: This line says, Work through all of the contents of the element and perform any other transformations you need to on any tags you find. In this case, you don t want to transform the rest of the element. Rather, you want it to pass through unchanged. You ll see how this happens shortly. Adding the Footer The last lines in this code block add the footer after the unchanged element:

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Copyright Planetary Fun 2006. This creates a horizontal rule followed by the words Copyright Planetary Fun 2006. Unfortunately, because you re outputting to HTML 4.0, the

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tag transforms to

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. You end by closing the element to tell the XSLT processor that you ve finished working with the element. Transformation Without Change When the stylesheet applies the transformation, you want the remaining document contents to remain unchanged, including the , ,