SALT Forum publishes vectored profile

The connection between a vector-based markup graphics language and a tagged language for speech applications may not be immediately apparent. But some developers see a connection as they work to bring voice-oriented interfaces to a wider audience. In fact, an important group in speech standards moved recently to formally push the link between speech and graphics.

The SALT Forum last week published a SALT profile for the World Wide Web Consortium's (W3C) Scalable Vector Graphics (SVG) markup language. According to Forum spokesperson Rob Kassel, manager for emerging technologies at founding member company SpeechWorks, SVG with SALT enables developers to create sophisticated mobile applications for devices with easy-to-use speech interfaces.

"Device manufacturers were saying that they wanted to provide access to network-based content, but HTML is just too cumbersome and it doesn't scale well to the smaller screens," Kassel said. "We saw that SVG had caught their attention and that they seemed to be shifting to it as the markup language of choice because it lets them build applications that can then scale to fit on different screen sizes and resolutions."

SALT (Speech Application Language Tags) are extensions to HTML, XHTML and XML for voice recognition and synthesized speech and audio output. Basically, the SALT tags allow developers to add speech interfaces to Web content and applications using familiar tools and techniques. In "multimodal" applications, the tags can be added to support speech input, output and call controls, either as standalone events or jointly with other interface options such as asking a question while tapping the screen with a stylus. In telephony applications, the tags provide a programming interface to manage the speech recognition and text-to-speech resources needed to conduct interactive dialogs with the caller through a speech-only interface.

The SALT specification is designed to work equally well on traditional computers, handheld devices, home electronics, telematics devices (such as in-car navigation systems) and mobile phones. "SALT presumes a Web-based environment that will encompass both the speech-in-speech-out and multimodal aspects of speech-enabled applications," Kassel said.

Meanwhile, SVG is a vector graphics file format from the W3C that enables vector drawings to be included in XML pages on the Web. Unlike bitmaps, which are pixel-based, vector drawings will scale to the size of the viewing window.

SVG allows developers to render graphics on displays of varying size and resolution, and features a lightweight design that reduces computational requirements, making it particularly attractive to manufacturers of cell phones, PDAs and other portable devices, Kassel said. SVG with SALT can also be used to provide speech "hot spots" within a graphic or provide spoken commands for scrolling and zooming the display. In addition, it can be used to embed descriptive services for the visually impaired directly within a graphic, streamlining the workflow process.

The new SVG profile supplements the SALT 1.0 specification, which was contributed to the W3C by the SALT Forum and already includes profiles for use with the Extensible HTML (XHTML) and Synchronized Multimedia Integration Language (SMIL). XHTML combines HTML and XML into a single format for the Web, and enables HTML to be extended with proprietary tags. SMIL (pronounced "smile") is a format for delivering and synchronizing multimedia content on the Web; it was introduced by the W3C in 1998.

It will probably take a while for the W3C to issue a formal recommendation on the SALT Forum's SVG profile (several months at least and, based on the group's history, possibly much longer). However, Kassel said that developers shouldn't wait for the official ratification to begin utilizing SVG with SALT in their applications.

"We've published the SVG profile now, and we're hoping that people will take up that document and start implementing it and building applications with it," Kassel said. "It could function as a de facto standard until the true standard comes out from the W3C.

"Developers who are building Web applications should begin thinking about how to deliver those apps on portable devices," he added. "Things are moving very quickly in this space. The convergence of mobile phones, PDAs, wireless data and speech access is just around the corner. We're at the leading edge of that curve, and developers need to begin thinking about how they are going to deliver their applications on portable devices."

Founded in 2001, the SALT Forum is a group of companies working together to accelerate the use of speech technologies in multimodal and telephony systems. For more information, visit the SALT Forum at

The SALT profile for SVG is available on the SALT Forum's Web site at

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About the Author

John K. Waters is a freelance writer based in Silicon Valley. He can be reached at


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