Throughout the short history of the Internet, the "lingua franca" of the World Wide Web has been HTML, or Hypertext Markup Language — the slowly evolving programming code that defines how Web pages are displayed on-screen.
But a new tongue is rapidly gaining traction as the Web's next-generation Esperanto. Extensible Markup Language, or XML, offers interactive-TV and broadband developers a powerful tool: Flexibility in handling data from multiple sources, such as a news feed fresh off the wire or a picture from a graphics library.
At its core, XML is a document-processing standard developed by the World Wide Web Consortium (3WC), which also oversees the development of HTML. XML's roots stem back to the much more sophisticated Standard Generalized Markup Language (SGML), first developed in the 1980s.
Unlike HTML, XML permits content developers to create and format their own document or page structure. HTML relies on a rigid set of markup tags (for example, &table>, &image> or &head>). But XML employs document type definitions (DTDs) and style sheets that enable developers to create their own tags (such as &picture>, &video>, &latenight>, &localsports>, &premium.price>, or anything else appropriate to describe the content).
A document's DTD defines that page's structure and rules.
Theoretically, content with descriptive XML tags — a magazine article, price list or program guide information, for instance — can be shared more easily across different print, broadcast, wireless and Web mediums. This "data portability" becomes critical in an environment in which data such as weather information, stock quotes or TV listings would be displayed on computers, handheld devices, cell phones or TV sets.
So far, Web developers have adopted XML as a tool to update Web pages using information stored in a database. For example, Bravo uses XML to update the "Now Showing on Bravo" section of its home page, which is changed throughout the day.
And Cable News Network Interactive uses XML as a data-exchange format, said vice president of strategic applications and systems development Keith Frey. News providers are starting to provide XML feeds and CNN now provides its syndication customers with XML output, Frey noted.
Though XML application development is still in its infancy, Microsoft Corp. — the world's largest software company — has already adopted it as the core of its sweeping .Net initiative, said Microsoft TV director of marketing and communications Ed Graczyk.
Microsoft uses ".Net" to refer to its ambitious plan to channel information anytime, anywhere via any device.
ITV developers are using XML to aggregate information for specialized applications. Canal Plus S.A. is experimenting with XML-enabled data to build individual portfolios or magazine-style content based on a subscriber's preferences.
OpenTV Corp. supports XML in its publisher-development application, which can take XML data files, extract the relevant information and insert it into an OpenTV application template.
This allows for an application to be built on the fly and then sent out via a broadcast signal, explained OpenTV vice president of strategy and product marketing Anup Murarka.
In Spain, OpenTV has developed an application that uses XML data to display soccer scores while a match is still being played. It's also developed a personalized teletext application for U.K. direct-broadcast satellite provider British Sky Broadcasting Group plc that's regularly updated with news articles, horoscopes and travel information.
Using XML in this way is "a key part of our publishing solution," said Murarka.
Microsoft uses XML for its Microsoft TV Server suite of applications, which deliver information to electronic program guide and electronic-mail applications, said senior product manager Esteban Sardera.
The software giant has developed a special XML-based rendering language that optimizes HTML pages for TV output. Canal Plus has also developed a dynamic rendering application using XML.
Microsoft TV also uses XML to process information from third parties (such as search engine results) and render such data for the client, or set-top box, for output to the TV screen.
Data exchange aside, another obstacle to wider adoption of XML for TV applications is the development of ITV- specific DTS. Microsoft has done some work in this regard, said Sardera, but the company hasn't publicly discussed its strategy, which may include proposing TV-specific DTDs to the W3C.
Crafting a standard set of ITV definitions is important in moving XML beyond its current applications and toward use as an actual layout engine, Muraka said, "Using XML for presentation is just going to take some time to standardize," said Muraka, who added that deciding which DTDs will be used and adopted is "going to take some time to develop and come to an agreement on."
