XSLT Cookbook, 2nd Edition

Chapter 5. Selecting and Traversing

I choose a block of marble and chop off whatever I don’t need.

Francois-Auguste Rodin

I have [traversed] the length and breadth of this country and talked with the best people, and I can assure you that data processing is a fad that won’t last out the year.

The editor in charge of business books for a major publishing company, 1957

Introduction

Doing anything remotely interesting in XSLT involves two related operations: determining which XML nodes to visit (selecting) and determining in what order you want to visit them (traversing). Selecting is largely in the domain of XPath, a separate specification but one intimately related to XSLT. Traversing is a function of built-in control structures of XSLT and how you organize your templates to harness them.

XSLT veterans are unlikely to find much revelation in this particular chapter. Nevertheless, it is important for two reasons. First, the ideas presented in these recipes distinguish XSLT from other programming languages and therefore tend to be things that trip up novices on their first attempts to master XSLT. Second, the examples covered in this section are the primitive building blocks of many more complex recipes covered in later chapters. Virtually everything one does in XSLT involves application of selection and traversal. By analogy to cooking, knowing how to make a good brown stock is a prerequisite to making a sauce espagnole!^[1] This chapter is comprised of examples of the “brown stock” variety ...