Frequently Asked Questions About Dynamic HTML

Microsoft's implementation of Dynamic HTML is supported in Microsoft® Internet Explorer 4.0. Dynamic HTML features include:

Document Object Model (DOM). Dynamic HTML provides a comprehensive object model for HTML. This model exposes all page elements as objects. These objects can easily be manipulated, by changing their attributes or applying methods to them at any time. Dynamic HTML also provides full support for keyboard and mouse events on all page elements. Support for the Document Object Model enables dynamic content, style, and positioning effects as well as data binding and scriptlets.

Data Binding. Data-driven application front ends can be built that present, manipulate (for example, sort or filter), and update data on the client without numerous round-trips to the server.

Scriptlets. A scriptlet is a Web page, authored with Dynamic HTML, that content providers can use as a component in their Web applications. With scriptlets, content providers can author content once, and easily reuse the content in other Web pages or applications.

Web developers, designers, and HTML authors will be able to take advantage of Microsoft's implementation of Dynamic HTML through a wide variety of third-party and Microsoft tools. Third-party tools currently supporting Microsoft's implementation of Dynamic HTML include: Bluestone Sapphire/Web 4.0 (beta), ExperTelligence WebberActive 4.0, SoftQuad HoTMetaL PRO 4.0, and Pictorius iNet Developer 2.0. Microsoft FrontPage™ 98 and the next major release of Microsoft Visual InterDev™ will also support Dynamic HTML.

Dynamic HTML enables authors to create pages based on HTML and script that download more quickly, with fewer Java applets and ActiveX controls. Microsoft's implementation of Dynamic HTML page loading is also asynchronous, allowing users to read or interact with the document while further downloading is taking place.

Microsoft's implementation of Dynamic HTML is a feature in Microsoft Internet Explorer 4.0. Dynamic HTML will also be a freely redistributable component that third parties can incorporate in their applications.

Microsoft is delivering the foundation for Dynamic HTML, the Document Object Model, across all platform releases of Internet Explorer 4.0, including the Windows® operating system, Macintosh® and key commercial UNIX platforms. In addition, all versions of Internet Explorer 4.0 will support scriptlets and tabular-based data binding through the Tabular Data Control.

Over 1000 Web sites are using Microsoft’s implementation of Dynamic HTML to present interactive content to users. Microsoft is supporting developers and designers through online forums and mailing lists. See the Mailing List home page for more information.

Microsoft's implementation of Dynamic HTML supports these W3C specifications:

• HTML 4.0 Working Draft (http://www.w3.org/TR/WD-html40/ )
• CSS1 Recommendation (http://www.w3.org/TR/REC-CSS1 )
• CSS Positioning Working Draft (http://www.w3.org/TR/WD-positioning )

Prior to Dynamic HTML, changing a page's structure, content, or style after the page loaded required requesting a new page from the server. This slowed the Web experience for end users, and also required authors to write multiple pages.

With Dynamic HTML, content providers can access and update all page elements at any time, without a server round-trip. This increases creative control for Web developers and authors, and makes the Web experience faster and more interactive for end users.

In August 1996, Microsoft and SoftQuad proposed to the W3C the Document Object Model, the basis for Microsoft's implementation of Dynamic HTML. Microsoft is continuing to work with the W3C Document Object Model Working Group to define a standard for this technology.

Last April, the Working Group published a preliminary requirements document for the Document Object Model at http://www.w3.org/pub/WWW/MarkUp/DOM/ . This was followed in early October by the Core Level 1 Document Object Model Working Draft . Microsoft's implementation of the Document Object Model is consistent with the direction of the W3C in that it allows authors to locate and access all elements of a document.

• HTML specifies contextual information and content for a Web page, including headings, forms, tables, paragraphs, links, and more.
• Cascading Style Sheets (CSS) specify the presentation of this content.
• Dynamic HTML, through the Document Object Model, provides an object model and API to allow interaction with HTML elements or CSS information.

So, for example, an author uses HTML to specify that there is a table, CSS to control the style/presentation of the table, and Dynamic HTML to update the contents of the table or its presentation.

Web developers and authors need to evaluate several tradeoffs when deciding which technologies to use in their Web applications. The use of HTML, scripting, and scriptlets ensures that applications can be widely deployed over a heterogeneous mix of clients and that a large number of authors and developers can easily create these applications. With components such as controls or applets, application development requires coding, which can be significantly more difficult than authoring. The use of these components enables greater Web application functionality, at the cost of reducing the number of people who can incorporate or build them.

Many of the CSS-based interactive features in Microsoft's implementation of Dynamic HTML gracefully degrade to a static experience in earlier browsers. For instance, instead of viewing a table of contents that is automatically generated, expanded, or contracted using Microsoft Internet Explorer 4.0, a Microsoft Internet Explorer 3.0 user will see the entire table of contents when the page is loaded. This degradation allows authors to write and publish a single page to target previous versions of browsers.

Both technologies support the W3C CSS Recommendation and CSS Positioning Working Draft . However, Microsoft's and Netscape's technologies fundamentally differ, because Microsoft's implementation of Dynamic HTML, based on the Document Object Model, provides greater creative control than Netscape's implementation of Dynamic HTML, which provides little support for the Document Object Model.

Netscape's version of Dynamic HTML in Navigator 4.0 exposes few page elements as objects, limiting layout and creative capabilities for authors. Page elements can be manipulated only while the page is loading, not after load time. Netscape's nonstandard implementation consists of JavaScript Accessible Style Sheets (JASS), layers, and dynamic fonts (TrueDoc). These technologies are not supported in Microsoft Internet Explorer 4.0.

Microsoft's implementation of Dynamic HTML also includes functionality, such as data binding, that is not supported by Netscape 4.0.