hat's the latest sleeper technology that promises to make your life easier? It's XQuery (short for XML Query) and it's the 'Ginsu knife' of XML standards.

XML can represent almost anything—files, graphics, Web services, etc. As developers store more and more information in XML format, they also have an increasing need to be able to search and update XML documents. Unfortunately, query language evolution hasn't quite kept up with XML's increasing popularity. Until recently, the available search technologies didn't meet developers' needs; full text search was too simplistic, and SQL was suitable only for relational databases. XML needed a new query language. Just as XML has the ability to describe virtually any data source, its query language needs to have the expressive power befitting a universal query language for disparate data sources.

The Worldwide Web Consortium (W3C) began working on the problem in October of 1999. The result of that effort is the XQuery language. XQuery is something of a hybrid—a powerful language with grammar similar to SQL, but more widely applicable.

The creators of XQuery went beyond basic search and update capabilities. XQuery also provides information integration and transformation capabilities.

The creators of XQuery went beyond basic search and update capabilities. XQuery also provides information integration and transformation capabilities. An XQuery implementation can search multiple back-end systems and combine results, effectively integrating multiple sources of information. XQuery can also transform the content and structure of XML documents. You can use XQuery expressions such as element and attribute constructors to express the structure of the result document. With transformation powers that rival XSLT, XQuery goes where no query language has gone before because it not only provides query results, but can also prepare those results for presentation.

XQuery is timely not just because XML's popularity is on the rise. It's an all-in-one tool that does more for less—perfect for these tough economic times. The remainder of this article presents five application scenarios that use XQuery to solve real problems. It's our hope that even if your application development needs don't precisely match these scenarios you'll still glean some of XQuery's capabilities and perhaps get some ideas about how you might be able to use XQuery in your own applications.