Extending XMLMap: XML for Presentation Purposes (2/2) - exploring XML
Extending XMLMap: XML for Presentation Purposes
Web pages developed quickly beyond text to integrate other media types, such as vector graphics, three-dimensional data, and streaming audio and video. The W3C was bombarded with proposals for describing vector graphics in XML. Microsoft submitted Vector Markup Language (VML) which is integrated into Internet Explorer 5 and above, Adobe modeled Precision Graphics Markup Language (PGML) after PDF, and there is also a Web-enabled format of the popular Computer Graphics Metafile (CGM) format.
The W3C decided to take IBM's draft of Scalable Vector Graphics (SVG) as a basis and enhance it with ideas from the other submissions. SVG took the same route as XHTML and was modularized in version 1.1 to fit various device profiles. Adobe produced a browser plug-in for SVG.
Virtual Reality Markup Language (VRML), pushed by SGI, was poised to transform the Web into a three-dimensional medium, but takeup was poor despite plug-in availability, probably because of the complexity involved in designing and implementing 3D applications. The Web3D organization tried to fix this with X3D. It replaces VRML, but also provides backward compatability and addresses the limitations of VRML. X3D is also the technology behind MPEG-4's 3D support.
With all these different media types making up a Web page a means of synchronizing them was needed, and created in the form of Synchronized Multimedia Integration Language (SMIL). SMIL describes the placement of various components that make up a page, and their timing if applicable. It was first implemented in RealMedia's RealPlayer, and there is a XHTML+SVG+SMIL profile for interactive media on pocket devices.
XML for Voice
The other presentation domain affected by XML was voice, previously dominated by proprietary formats and platforms. The increasing pressure of interoperability between equipment manufacturers and software developers led to the definition of XML formats across the whole board of voice application elements.
The most mainstream format is VoiceXML, which can be used to define the flow of voice applications, including menus, speech recognition, synthesized speech, and playback. Call Control Extensible Markup Language (CCXML) is designed to provide telephony call control support for VoiceXML or other dialog systems.
Speech Application Language Tags (SALT) are a lightweight set of extensions to existing markup languages, in particular HTML and XHTML. They enable multimodal (i.e. via keyboard, mouse, pen, or microphone) and telephony access to information, applications and Web services from PCs, telephones, tablet PCs and wireless personal digital assistants (PDAs).
Presenting information with HTML was the killer application for Markup Languages in the mainstream area. Refining this success with the stricter XML foundation for hopefully greater interoperability and leaner implementations was a natural consequence. While takeup of the different XML formats varies, they build a solid foundation for anything presentation-related.
Produced by Michael Claßen
Created: Jan 20, 2003
Revised: Jan 20, 2003