Is HTML+Time Out-of-Sync With SMIL?
October 7, 1998
The new multimedia submission from Microsoft et al called HTML+Time covers some of the same ground as SMIL (Synchronized Multimedia Integration Language), an application of XML for the synchronization and integration of Web-based multimedia sources. It offers an alternative SMIL-like syntax that is integrated directly with current HTML syntax.
Although SMIL has been a W3C Recommendation since June 1998, Microsoft is still reluctant to support it. Citing failings with SMIL, Microsoft has teamed up with Compaq and Macromedia to develop the HTML + Time submission. The three companies seek to position HTML+Time as an easier way for authors to add time-based presentation effects to Web pages than using an external, XML-based document.
HTML+Time extends HTML by adding a set of time-based attributes to its existing tag set. There are a few HTML+Time effects that are not yet achievable via SMIL. Although these "new features" don't in themselves seem to warrant an entirely new standard, many admit that SMIL could use a bit of polish. SMIL has been implemented by a number of groups with great results, but SMIL doesn't provide for everything under the sun in web-based media, and SMIL v1.0 was only meant to be a start.
"HTML+Time offers important improvements to SMIL, especially with regard to how SMIL will be adopted in browsers, which is its current limitation," explains Jeremy Allaire, whose company develops two different popular HTML development tools: Cold Fusion Studio and Home Site.
Meanwhile, Microsoft has remained consistent with what they've been saying since SMIL was approved in June. In Microsoft's view, SMIL has reached Recommendation status a bit prematurely, providing an XML-based syntax for synchronizing multimedia for a Web still largely dominated by HTML-based documents.
"SMIL is a stand-alone, XML-based format for describing a multimedia presentation," explains Steve Sklepowich, Microsoft's Product Manager for Platform Marketing. "The concepts are good, but the approach was wrong. They went off and did their own layout language."
According to Sklepowich, the HTML+Time spec has two main priorities. The first is applying time attributes to any arbitrary HTML element. Such "core" functionality includes specifying information such as a streaming media element's begin time or the length of its duration. The second goal is to use these same attributes to provide a means of describing that same media element's integration with other multimedia elements of a presentation. "Neither of those things is possible using SMIL," Sklepowich added. He also noted that the SMIL spec also neglected to reference an object model (which most HTML authors would require).
"HTML + TIME is based on HTML for display and CSS for positioning and style reuse. Through the HTML DOM, all the elements in the page can interact with each other, and participate in the presentation. In contrast, SMIL presentations play in their own region of the HTML page, and have no interaction with the rest of the Web page," Sklepowich says. "Regardless, SMIL-based presentations and HTML+TIME-based presentations can coexist in the same Web page."
Webdeveloper.com's Scott Clark also confirm's that SMIL's strategy has a few holes. "SMIL will not, (although it should) allow interaction between objects," he confirms.
But Clark points out that SMIL's object model neutrality was a feature of SMIL, and not an oversight, and that SMIL does enable applying time attributes to HTML elements, similar to the way that style sheets apply formatting properties. Also, CSS2 stylesheets can be combined with SMIL documents to control presentation effects.
For many developers, time-based media clips are precisely the kind of data they wish to define in a separate document. Externalizing the description of such data can often result in greater control overall. "By providing this control through the use of an external document, SMIL can make the development and management of multimedia Web pages a more streamlined, efficient process," Clark explains.
How Far Can You Extend HTML?
HTML+Time seems to re-unify the very same content and presentation elements that various W3C groups have been working so hard to separate from HTML over the last two years. It raises questions about the future direction of HTML.
"The W3C is now working on the next generation of HTML as an application of XML," explains Dave Raggett, the W3C's HTML lead. "The driving motivation behind HTML+Time is to give content providers easier ways to schedule dynamic effects in HTML pages, but the approach also has value beyond HTML."
"It is too early though to see which direction will win out - adding timing attributes to HTML or as properties to style sheets, both approaches have their attractions," Raggett explains.
According to Raggett, SMIL is great for timing media clips, e.g. presenting an HTML document along with an audio comentary and accompanying images. It doesn't however, give designers the ability to control timing down to individual elements in an HTML document. This means with SMIL you can't apply different timing to individual bullets in an HTML list, for example.
One of the recent considerations of the HTML working group has been trying to reduce the costs of producing web content by shifting the burden to authoring tools. Hopefully the next generation of authoring tools will succeed at meeting a challenge the current generation of HTML tools failed to live up to: producing content that can be easily repurposed for a wide variety of client devices.
It remains to be seen whether multimedia timing information will be specified as markup or via style sheets. Presently it would appear that factions are split over which technical approach is better for creating Web-based multimedia presentations.
"The process of submission and development of the HTML+Time specification is somewhat suspect insofar as the leading SMIL proponents were not involved," Allaire explains."Ultimately, it would appear that some synthesis of the actual SMIL specification with the improvements found in HTML+Time will be the outcome. In the mean time, with SMIL a deployed W3C standard, we've gone out of our way to support it in our authoring tools."
This seems to be the sentiment in the industry, but if HTML+Time is incorporated first into the browser, it could be a setback for SMIL. It would also mean that the Web will extend reuniting content and presentation into the next generation of HTML.