This chapter is intended to serve as a comprehensive reference to the Extensible Markup Language (XML) W3C recommendations for both XML 1.0 and 1.1. We have made every effort to cover the contents of the official W3C document exhaustively. However, if you are implementing an XML parser, editor, or other tool, you should also review the latest revision of these recommendations on the Web at http://www.w3.org/TR/REC-xml and http://www.w3.org/TR/xml11/. This book refers to the XML 1.0 Third Edition dated 04 February 2004 and the XML 1.1 Recommendation dated 04 February 2004, which was edited in place 15 April 2004.
The endorsement of the Extensible Markup Language (XML) 1.1 Recommendation in February of 2004 has introduced some challenges within the XML community. The markup language described by 1.1 is not precisely a superset of the language described by Version 1.0, which means that some documents that are well-formed under 1.0 rules will not be well- formed under 1.1 rules. The main narrative of this chapter adheres to the rules laid out by the 1.0 Recommendation. Notes such as this one will appear when necessary to outline the differences between XML 1.0 and XML 1.1.
When deciding which version of XML is appropriate for your application, consider that unless you specifically need to use markup names that contain characters not available in Unicode 2.0, XML 1.0 will most likely be the correct choice.