XQuery

XQuery Versus XSLT

XQuery and XSLT are both languages designed to query and manipulate XML documents. There is an enormous amount of overlap among the features and capabilities of these two languages. In fact, the line between querying and transformation is somewhat blurred. For example, suppose someone wants a list of all the product names from the catalog, but wants to call them product_name in the results. On the one hand, this could be considered a query: "Retrieve all the name elements from the catalog, but give them the alias product_name." On the other hand, it could be considered a transformation: "Transform all the name elements to product_name elements, and ignore everything else in the document."

Figure 25-1. XQuery, XPath, and XSLT

Shared Components

The good news is that if you've learned one of these two languages, you're well on your way toward learning the other. XQuery 1.0 and XSLT 2.0 were developed together, with compatibility between them in mind. Among the components they share are:

The data model

Both languages use the data model described in Chapter 2. They have the same concepts of sequences, atomic values, nodes, and items. Namespaces are handled identically. In addition, they share the same type system and relationship to XML Schema.

XPath 2.0

XQuery 1.0 is essentially a superset of XPath 2.0. XSLT 2.0 makes use of XPath 2.0 expressions in many areas, from the ...