Foreword

XPath 1.0 is the World Wide Web Consortium (W3C) recommended language for accessing information in XML documents. XPath provides the core functionality necessary to access XML documents: path navigation of an XML document to identify XML values of interest; selection of XML values that satisfy predicates; and extraction of the selected XML values. Given the breadth of these requirements, it is surprising that developers of XML applications do not have numerous languages to choose from. Luckily, XPath 1.0 meets all these requirements with a concise , intuitive syntax that makes it easy to use and to incorporate into other XML technologies. XPath 1.0 is most commonly used as an embedded language in XSLT 1.0, the extensible stylesheet language used to transform XML into HTML, and it is also used in XML Schema 1.0, XLink, and XPointer.

In XPath Kick Start , Steven Holzner provides a thorough introduction to XPath 1.0 and its many uses in other XML technologies. The first five chapters flow from a gentle introduction for readers entirely new to XML and XPath to a hands-on guide to using XPath 1.0 in XSLT 1.0. By the end of Chapter 5, the reader will be able to write non-trivial XPath expressions and understand how to apply them effectively to write useful XSLT stylesheets.

In Chapters 6 through 8, Steven introduces XPath 2.0, which at the time of this writing, is a W3C Last Call Working Draftjust two short steps from Recommendation status. For current XPath 1.0 users, the most significant addition in XPath 2.0 is support for XML Schema. XPath 2.0 recognizes and respects the strong type information of schema- validated documentsfor example, XPath 2.0 can distinguish dates from inventory numbers from currency valuesbut preserves much of XPath 1.0's flexible support for schema-less, well- formed documents. Like XPath 1.0, XPath 2.0 is already a significant part of other XML technologies. XQuery 1.0, the W3C query language for XML that is also a Last Call Working Draft, contains all of XPath 2.0 as a proper sub-language. XPath 2.0 is such a large part of XQuery 1.0 that by the end of XPath Kick Start , the reader will have learned yet another important XML technology.

Given XPath's already significant and growing impact in numerous XML technologies, getting a kick start on XPath is a valuable investment for any XML-application developer.

Mary  Fernandez
Principal  Technical  Staff  Member
AT&T  Labs  Research

Co-editor  of  the  W3C  working  drafts:  XQuery  1.0  and  XPath  2.0  Data  
Model,  XPath  2.0,  XQuery  1.0,  and  the  XQuery  1.0  Formal  Semantics