Developers Like DHTML, but Many Wait

Rick Dobson

New-and-improved versions of HTML promise more dynamic Web sites without requiring expertise in writing Java applets or ActiveX controls, but incompatibilities are causing developers to wait for a uniform standard. Both Netscape and Microsoft call the improved versions Dynamic HTML (DHTML). But despite sharing the same name, the two implementations differ substantially.

DHTML represents the combination of HTML, cascading style sheets (CSS), and scripting languages. How do the three differ? Basically, HTML specifies elements such as a heading or a paragraph. CSS gives content authors precise control over the presentation of th at element. DHTML, through the Document Object Model (DOM), provides a model and API to let an author manipulate the HTML and CSS.

Netscape supports DHTML in Communicator 4.01, which is available for the Mac, Windows, and Unix. Microsoft's support will arrive with the imminent release of Internet Explorer 4.0, but Unix support will follow Windows and Mac support by about 180 days. For more information on the differences between the two DHTMLs, see the table .

Lauren Wood, chair of the World Wide Web Consortium's DOM working group, says preliminary specifications for key elements of the W3C's DOM, a standard for how programs and scripts will dynamically access and update documents, will be available in August. Those elements include functionality for document navigation and manipulation, and possibly style manipulation. However, Wood estimates that the W3C won't issue its final recommendation until sometime in 1998.

"DHTML will permit Web-site development with richer multimedia effects and more interactivity," says Sal Arora, technical products manager at NetObjects. Ne tObjects markets Fusion, a Web development tool for those who want to spend more time developing content than writing HTML. NetObjects says it is working with Netscape and Microsoft DHTML versions.

However, others are waiting. Ed Foreman, marketing manager at Elemental Software, which markets the Drumbeat dynamic Web-site authoring program, says he is "taking a wait-and-see stance on DHTML" and is recommending the same for his clients. Like many bleeding-edge technologies, DHTML offers significant innovation. Developers who can't resist the call of the wild may find it best suited for small intranets or extranets, where it is possible to mandate the use of a single browser type. Others may want to gain experience with DHTML by experimenting with one version or the other in anticipation of the release of the final specification.

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Dynamic HTML Comparisons

Dynamic HTML Compariso ns
Features	Netscape Communicator 4.01	Microsoft Internet Explorer 4.0 Preview
Cascading style sheets (CSS) Level 1 recommendations (CSS gives authors control over document style [e.g,. which fonts and colors to use]).	* Can change style with an on-load event. Netscape's implementation allows style changes only as a page loads.	* Can change style during and after an on-load event. Microsoft's approach permits dynamic styles during and after the loading of a page.
CSS positioning (lets authors code drag-and-drop behavior for objects on a page and enables object movement in 3-D).	* Positions HTML elements with CSS. * Also enables positioning through Layers tag.	* Positions HTML elements with CSS.
Document Object Model (a DOM interface lets programs or scripts dynamically access and update a document's content, structure, and style).	* Permitted for a subset of HTML tags and attributes accessible through Netscape JavaScript object model.	* Permitted for all HTML tags and attributes -- even characters associated with tags.
Language support (scripts, in any language, manipulate object properties and methods to produce dynamic content in response to user-generated events).	* DOM accessible by European Computer Manufacturers Association (ECMA) standard JavaScript only.	* DOM accessible by ECMA JavaScript and VBScript.
Event bubbling (can reduce code length when you need to manipulate many objects the same way [e.g., drag and drop multiple items]).	* No event bubbling.	* Event bubbling supported.
Data binding (enables faster data-based Web experiences by reducing the need to refresh data from a server).	* No implementation.	* Cache server-based data locally. * Sort and filter data without serve r. * Supports ODBC, JDBC, and comma-delimited data.