XML (Extensible Markup Language)

By the early 2000s, Extensible Markup Language (XML) was fast emerging as the lingua franca of the World Wide Web, augmenting and superseding Hypertext Markup Language (HTML), the dominant language for encoding content since the Web's inception. HTML was increasingly viewed as too basic and inflexible to effectively transmit and format new forms of Web information, particularly the highly structured data needed for business-to-business e-commerce.

While XML is popularly known as a language, experts call it a metalanguage—a grammar that defines the language's rules and processes. Whereas HTML employs a limited number of set tags to define the form of Web-based content, XML is nearly infinite in its capacities to define not only the form but also the content itself. This means there is no single, universal collection of tags that make up XML: individual users, companies, industries, and other groups are able to define new languages and attributes appropriate to their specific needs.

Technically, XML doesn't replace HTML, but envelopes it. XML's flexibility makes it compatible with the existing HTML infrastructure while allowing for greater integration with other forms of electronic data. XML thus streamlines the transfer of data across networks, systems, and computer platforms and defines form and content both on the Web, for hard copies, on CD-ROM, and in other media.

Unlike HTML, XML tags aren't primarily presentation-oriented. Rather, well-formed XML—a phrase insiders use to describe tag schemes that employ XML's full powers and best practices—uses tags to influence the look, function, and meaning of content. The organization of a document is set by a document type definition (DTD), allowing it to appear in formats appropriate to the technological needs and capabilities of whoever is viewing the document. To tailor the document to its required form, it is mediated by parsing software that reads its DTD and translates the document into the medium required. In other words, the parser, rather than the medium (such as a Web browser), actually reads and interprets the document.

The World Wide Web Consortium (W3C) launched its XML Working Group in September 1996 to devise improved methods of organizing and integrating data, and to work towards harmonizing tag-naming conventions to avoid overlap that could confuse XML parsers. XML Version 1.0 was rolled out in December 1997 as a W3C recommendation, and the organization ratified XML as a standard the following February. A revised edition was released in October 2000, still known as XML 1.0. In 2001 the W3C formally adopted a DTD standard replace the existing business-created DTDs developed for the exchange of business documents using XML.

One key benefit of XML that emerged in the early 2000s was facilitating data integration between markets, leading to greater convergence of online marketplaces and business-to-business e-commerce. By allowing a common framework through which different methods of organizing and sharing information over networks are made compatible, XML helps bridge data communication between industry groupings that previously developed their own, mutually exclusive networks.

Speed-bumps to XML adoption persisted in the early 2000s. Some parsers, for instance, remained excessively strict in their translation of XML documents. But most analysts expected these problems to be largely ironed out, and many expected XML to become the document-transfer standard by the mid-2000s.