XML a cornerstone of new graphics model
After more than a year of revisions, the World Wide Web Consortium recommends specifications for graphics and animation that could give popular Web technologies a run for their money.
The W3C recommended SVG (Scalable Vector Graphics), advancing it from "candidate recommendation" status where it has spent the last 13 months having its tires kicked by the Web graphics world.
The specification, first proposed in January 1999, is designed to make lightweight images that can fit any screen--from cell phone displays to large monitors.
Another goal of the technology is to integrate graphics more tightly with documents on the Web. Based on XML (Extensible Markup Language), a software method that lets anyone set up standard ways of describing digital documents, SVG can be included alongside data and text and manipulated by XML authoring tools.
Because it's written in XML, SVG is better able to make graphics searchable and digestible by screen readers, a boon for Web authors struggling to comply with increasingly strict accessibility requirements for people with disabilities.
Accompanying SVG is the recommendation of SMIL Animation. Pronounced "smile," SMIL (Synchronized Multimedia Integration Language) lets Web authors sync up sound, text and other multimedia elements using simple tags rather than programming code.
SMIL Animation expresses common Web animations such as mouse rollovers in XML instead of less-flexible scripting languages. It accomplishes the types of lightweight effects made popular on the Web by Macromedia's Flash animation technology.
"Flash has shown that there is a definite need for vector graphics," said Chris Lilley, graphics activity lead for the W3C. "What people have found is they have existing XML infrastructure. So by using the same XML infrastructure for graphics as they are using for text and data, you can use the same tools. That's very powerful--it means it's no harder to have a graphical view of something than it is to have a textual view."
Vector graphics are images that computers can render from a set of geometric descriptions instead of pixel-by-pixel bitmap formats such as JPEG or GIF. Because vector graphics are mere abstract descriptions, they can fly through tight bandwidth connections that typically choke on bulky image files.
Vector graphics also can be easily resized to suit their destinations, making the technology potentially attractive to Web authors tailoring their pages to fit a variety of different Web-surfing devices, including small appliances such as telephones.
SVG emerged as a Tower of Babel threatened to rise from competing efforts to standardize vector graphics. These included
• Web Schematics, designed for making flow charts and other diagrams
• Adobe Systems' PostScript-based PGML (Precision Graphics Markup Language), best suited to graphics such as bar charts, logos and screen graphics such as push buttons
• the Microsoft-backed VML (Vector Markup Language), a text format for vector graphics, and
• DrawML, which resembles Web Schematics except that it relies heavily on Java, Sun Microsystems' cross-platform programming language, to lay out diagrams.
SVG established itself as a consensus alternative. Its contributors include Adobe, AOL Time Warner and its Netscape Communications unit, Apple Computer, Autodesk, Bitflash, Canon, Corel, Eastman Kodak, Ericsson, Hewlett-Packard, IBM, Macromedia, Microsoft, Nokia, Openwave Systems, Opera Software, Quark, Sun and Xerox.