XQuery, 2nd Edition

Chapter 1. Introduction to XQuery

This chapter provides background on the purpose and capabilities of XQuery. It also gives a quick introduction to the features of XQuery that are covered in more detail later in the book. It is designed to provide a basic familiarity with the most commonly used kinds of expressions, without getting too bogged down in the details.

What Is XQuery?

The use of XML has exploded in recent years. An enormous amount of information is now stored in XML, both in XML databases and in documents on a filesystem. This includes highly structured data such as sales figures, semi-structured data such as product catalogs and yellow pages, and relatively unstructured data such as letters and books. Even more information is passed between systems as transitory XML documents.

All of this data is used for a variety of purposes. For example, sales figures may be useful for compiling financial statements that may be published on the Web, reporting results to the tax authorities, calculating bonuses for salespeople, or creating internal reports for planning. For each of these uses, we are interested in different elements of the data and expect it to be formatted and transformed according to our needs.

XQuery is a query language designed by the W3C to address these needs. It allows you to select the XML data elements of interest, reorganize and possibly transform them, and return the results in a structure of your choosing.

Capabilities of XQuery

XQuery has a rich set of features ...