Chapter 3. XQuery, XPath, and XSLT

Michael Kay

This chapter explores the relationships between XSLT, XPath, and XQuery. It explains why we need three languages rather than one and the way in which they are interrelated. For readers who might be familiar with XSLT, it explains the areas in which XQuery is similar to XSLT, and the areas in which it is necessarily different. It also explores some of the differences between transformation and query that affect the implementation architecture—in particular, the relationship to schemas and type definitions, and the differences in the way optimization is carried out in the two environments.