Platinum Edition Using HTML 4, XML, and Java 1.2
(Publisher: Macmillan Computer Publishing)
Author(s): Eric Ladd
ISBN: 078971759x
Publication Date: 11/01/98

Other than the specific elements mentioned in the preceding list—which are also contained in the introductory section of Netscape’s own Dynamic HTML documentation—Netscape has added other new features related to Dynamic HTML to version 4 of its Web browser. These include the changes to its JavaScript scripting language and to the Navigator Web Browser Object Model that supports these new capabilities.

Microsoft’s Answer

Microsoft’s answer to the “What is Dynamic HTML?” question is a bit longer than Netscape’s and reveals a greater number of new possibilities and capabilities of its Internet Explorer Web browser. Microsoft has very good documentation for its technologies at its SiteBuilder Network, located at

http://www.microsoft.com/sitebuilder/

The documentation for Dynamic HTML is located at the following location on Microsoft’s Web site:

http://www.microsoft.com/workshop/author/default.asp

The elements listed there as being a part of Microsoft’s version of Dynamic HTML are the following:

•  Dynamic HTML object model—The heart of Microsoft’s Dynamic HTML is its extensions to the Web Browser Object Model. As shown in Chapter 19, “The Web Browser Object Model,” previous object models for Netscape Navigator and Microsoft Internet Explorer enabled you to create scripts to interact with a small portion of HTML elements—images could be swapped, forms could be processed, hypertext links could be manipulated, and so on.
With Microsoft’s version of Dynamic HTML, it has extended the Web Browser Object Model to include every HTML tag. Therefore, events such as responding to mouse movements or keypresses can be attached to any element in an HTML document. The format and style of any element on a page can be dynamically changed, either separately or as a group. Not only can the format be changed, but the actual contents of an HTML tag can be changed—the text within a <P> paragraph container tag can be changed on-the-fly, without going back to the Web server, in response to a user action or some other event.

•  Dynamic content—Microsoft achieves dynamic content—the capability to change the displayed content of an HTML document without getting more information from a Web server—through its enhanced object model. Unlike Netscape Navigator, Internet Explorer also supports the dynamic redisplay of the content of a Web page when something on it has changed. Therefore, when something on a Web page is added, removed, or replaced, the other contents on the page automatically adjust themselves to display correctly.

•  Dynamic styles—As with Netscape, Microsoft’s Dynamic HTML achieves the capability to dynamically change the style of the contents of an HTML document through style sheets and its object model. In Microsoft’s Dynamic HTML, as implemented in its Internet Explorer Web browser, whenever the contents (as described in the preceding item in this list) or format of a Web page are dynamically changed, the rest of the document automatically reformats itself to display properly.

•  Positioning—Microsoft uses CSS positioning and its object model to implement the precise positioning and repositioning of HTML elements. CSS formatting and positioning are the only aspects of Dynamic HTML that Netscape and Microsoft really share.

•  Data binding—Data binding is a way of attaching data from an external source to an HTML element. In addition to using special new attributes to certain HTML tags, data binding makes use of Microsoft’s ActiveX Control Data Source Object. In this way, for instance, an HTML table can be filled with data from an external file, such as a flat ASCII file or database, through the Data Source Object. Methods of that object can then be called to sort the data using any of the columns of data.

•  Multimedia effects—Microsoft also uses its ActiveX Control technology to add multimedia effects to its Dynamic HTML. You can add filters to your document to create visual effects or use Microsoft’s DirectAnimation system to easily add animations. The effects possible with Microsoft’s filters and other technologies are similar to those offered by animated GIFs or Shockwave; because they are built into the Web browser, however, you can often achieve these possibilities much more simply.

In addition to the topics covered in the preceding list—the only technologies listed by Microsoft as part of its implementation of Dynamic HTML—Microsoft has other technologies that add related capabilities. For instance, Microsoft has its own system for embedding and downloading fonts into an HTML document. Although this technique is not technically considered part of Microsoft’s Dynamic HTML, it is discussed in the “Dynamic Fonts” section later in this chapter and compared with Netscape’s system.

The World Wide Web Consortium’s Answer

For the most part, the W3C considers the bulk of the Dynamic HTML implementations introduced by Netscape and Microsoft to be extensions to the Web Browser Object Model (also known as the Document Object Model, or DOM). The W3C has undertaken the task of developing a DOM standard, but its work on that topic is not as far along as its work on other standards. You can find out where it stands on a Document Object Model standard by looking at

http://www.w3.org/DOM/

As of August 18, 1998, the W3C has released a Document Object Model Level 1 Proposed Recommendation. Until the W3C’s specification is officially released, the efforts and advances of Netscape and Microsoft with Dynamic HTML will likely continue to diverge. Only the market and the efforts of the community of Web developers will determine which technologies survive and thrive.

Web Page Layout and Content Positioning

Because of their support for the W3C’s CSS standard, most similarities between Netscape’s and Microsoft’s Dynamic HTML technologies occur with the elements that make use of style and style sheets. The main use of style sheets, discussed extensively in Chapter 9, “Style Sheets,” is in the specification of formatting information for HTML elements. The benefit of using style sheets for this purpose is the capability of the Web page designer to separate the content of the document from its formatting information. (This makes it much easier to change the format while keeping the information the same.)