XML (eXtensible Markup Language): An Overview
As web developers know all too well, basic HTML (HyperText Markup Language) doesn’t provide any structure to Web pages, and the formatting is mixed with the content. To allow Web pages to be structured for automated processing (e.g. electronic commerce), the World Wide Web Consortium (W3C) developed an enhancement to HTML. The result were two new languages; one was XSL (eXtensible Style Language), and the other was XML (eXtensible Markup Language), a system for defining, validating, and sharing document formats on the Web.
XML is best known to many bloggers and Netizens as RSS (Rich Site Summary/Really Simple Syndication), which is actually a lightweight XML format used to share headlines and blog feeds.
The W3C, an organization devoted to developing the Web and standardizing protocols, formed an XML Working Group chaired by Jon Bosak of Sun Microsystems in 1996. Several key industry players who were also included in the working group were Adobe, Hewlett-Packard, Microsoft, Netscape, and Fuji Xerox.
The group published a working draft for XML in November of the same year. Two years later, the W3C announced the release of the XML 1.0 specification.
The year 1999 found the release of two W3C Recommendations on XML. The first was entitled Namespaces on XML, and the other was Associating Stylesheets with XML documents. In January of 2001, the Internet Engineering Task Force (IETF) released a Proposed Standard on XML Media Types.
XML is an open, human-readable text format derived from the Standard Generalized Markup Language (SGML). Originally meant for large-scale electronic publishing, XML is now being used in the exchange of various types of data on the Web and elsewhere. It is also becoming a language of choice for communication between application programs.
The XML Working Group’s design goals (taken from the W3C website) for XML were:
The markup language describes XML documents, which are a class of data objects. Moreover, XML also describes the behavior of software modules called XML processors. These are used to read XML documents and provide access to their content and structure.
Those familiar enough with HTML will find XML syntax a lot similar. However, don’t assume that coding in XML is painlessly easy — XML is stricter than HTML, and sloppy HTML coders will do well to remember that. Several reminders when coding in XML:
A good hands-on tutorial on XML can be found at W3Schools.com.