Features of Dynamic HTML

Changing Tags and Content

The capability to change tags and their content utilizes the Document Object Model, which uncovers everything for change, including all tags and style sheet attributes.

Live Positioning of Elements

There are several ways to move things around on the page after the page is loaded into the browser. First, the movement can happen automatically. Netscape's layers make it possible to incorporate slides, fades, and other animated effects. This is accomplished by hiding or moving each layer independently of the others to any position on the screen. The p

rocess of layering, also referred to as z ordering, makes it possible to download an entire site or section of a site at one time. Each layer represents one page, and because all the layers are loaded into the user's browser to begin with, no additional requests to the server are needed. As the user requests additional pages, the browser simply passes the requested pages to the top of the stack for viewing.

Z ordering come from the old x and y coordinate system you learned in high school geometry. Where x and y describe two dimensions (height and width), the z element describes the third dimension (depth).

The Microsoft approach is capable of the same types of effects, plus the movements of specific elements on the screen. Instead of moving a section of the Web page, the user can click on a single element, such as a graphic or plugin, and drag it to a new location on the page.

Dynamic Fonts

Netscape developed the idea of dynamic fonts, and it hopefully will catch on with other browsers. Just because you specify a font doesn't mean that the user has it on his or her machine. The end result is that the page developer just doesn't know how the page is going to appear.

You can try to work around the problem with style sheets or the tag by providing a list of fonts in order of preference, followed by a general type such as sans serif. This works, but not very elegantly. Netscape's way around this uses TrueDoc technology from BitStream. The result is font information in a highly compressed format that is downloaded with the page. The details of the font are stored in vector format, which is assembled on the fly using common information from a library on the user's machine.

Data Binding Data binding is one of the features Microsoft has worked hard to develop. Data binding enable page elements such as table cells to "attach" themselves to database records. With direct binding, this middle ground of database processing is passed over. Changes to a record are updated on screen, while user modification of information is passed back to the database for updating.

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