Preface

Extensible Markup Language (XML) is everywhere. In an astonishingly short period of time, XML has worked itself into the nooks and crannies of corporate IT departments, academic research institutions, and small-shop programming operations everywhere. As one of the authors of this book points out, XML now encodes a bewildering array of datatypes scattered across a large number of diverse application domains.

Where there's information, there are people who are going to need to query that information. Happily, XQuery has come along to provide a powerful and standardized way of searching through all that XML-encapsulated data. Going beyond Google, XQuery provides a flexible and easy-to-use mechanism for querying not only content, but structure as well. Drawing from XSLT, XQuery doesn't content itself with simply providing a query capability; it does transformations too. I believe that it will increasingly replace XSLT in a number of application areas (though XSLT aficionados needn't fear ”there are plenty of things to do for both technologies). Most interestingly, some of the data that XQuery will manipulate won't even have started life as XML: A large portion of the data that XQuery deals with will have started life in the form of rows and columns in corporate relational databases.