The specification, first proposed in January last year and originally slated for a summer 1999 proposed recommendation, promises to make Web graphics more flexible and lightweight, as well as more easily integrated with Web documents.
Vector graphics are images that computers can render from a set of geometric descriptions instead of pixel-by-pixel bitmap copies such as the common JPEG or GIF formats. Because vector graphics are mere abstract descriptions, they can fly through tight bandwidth connections that typically choke on bulky image files.
Vector graphics also have the advantage of being easily resized to suit their destinations. On that score, SVG comes at an opportune time for companies tailoring Web pages to fit a variety of different Web-surfing devices, including small appliances such as telephones.
Because photographs still require bitmap formats, vector graphics don't spell the end of bitmap images on the Web. To that end, SVG is designed to assimilate and more efficiently resize photographic images, according to the W3C.
SVG is written in Extensible Markup Language (XML), a W3C recommendation for creating specialized markup languages for the Web. Capitalizing on XML's capabilities, the W3C has made SVG's textual content, such as logos and labels, searchable and translatable, among other things.
"Businesses have a lot of data in XML," said Chris Lilley, W3C graphics activity lead. "This is being used for data, for text. Putting the graphic in XML means it can be manipulated using the same tools and as a unit with the text. It's a much higher level of integration."
SVG emerged as a Tower of Babel threatened to rise above vector graphics technologists. Work on the specification began as an attempt to synthesize the development of numerous competing vector graphics submissions that had made their way to the W3C by early last year.
These included Web Schematics, designed for making flow charts and other diagrams; Adobe's PostScript-based Precision Graphics Markup Language (PGML), best suited to graphics such as bar charts, logos and screen graphics like push buttons; the Microsoft-backed Vector Markup Language (VML), 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.
But the SVG soon took a course away from the existing proposals, according to the W3C.
"We looked at those things and PostScript and even VRML," Lilley said. "But you shouldn't think this has been a pulling together of existing specs. That's where we started from, and it was good to have something concrete to discuss. But this is a brand new specification. Over time it has become its own thing."
Lilley said SVG's delays were not the fault of the wide array of technologies originally under consideration. The problem instead had to do with making SVG compatible with both established and emerging W3C recommendations for animation and other graphical effects.
For example, in the process of hammering out SVG, working group members decided to cook up a whole new way of handing animations with its key multimedia synchronization spec, SMIL Boston.
Synchronized Multimedia Integration Language (SMIL, pronounced "smile") Boston lets Web authors sync up sound, text and other multimedia elements using simple tags rather than programming code. SMIL animation, as reported in November, is designed to do the same thing for animations, turning the business of common Web animations such as mouse rollovers over to an XML dialect rather than to less-flexible scripting languages.
Proceeding in tandem with SVG, SMIL animation is nearing its own candidate recommendation, with a final working draft posted earlier this week.
The W3C stressed that SVG has been making progress in the marketplace even while hung up in the working group. Implementations exist in products by both IBM and Adobe Systems, among others.
As part of the candidate recommendation phase, the W3C is calling for more implementations of SVG; it has released a test suite that developers can use to evaluate their SVG work.