HTML Versus DHTML

W3C also takes no stance on which language should be used as a default language, although it provides for a new META value to set the default for a specific page. For example, the following snippet sets the default for a Web page to JavaScript:

<META HTTP EQUIV="Content Script Type" CONTENT= "text/javascript">

If the META element is not included, the browser has the option of determining the default language. As a generally accepted implementation, script compatible browsers use JavaScript as the default scripting language.

HTML 4.0 also includes several other items which, while not directly part of the DHTML discussed in this book, will help the page developer create less static documents.

First on the list are two new attributes TITLE and TABINDEX. The first, TITLE, is added to existing elements and tags as a method for the user to request extra information or help. It includes strings of text which provides a note such as "Submit form to Server". How the string is displayed is up to the browser, but on Windows you can expect an implementation using tool tips and Macintosh versions will probably use help balloons. Another option for other platforms is the status bar.

The syntax to implement the title attribute is similar to the following:

<A href="http://www.w3.org/" title="World Wide Web Consortium Home Page">

The TABINDEX attribute sets a specific tabbing order for traversing among interactive elements (hyperlinks, form fields, and so on) on the Web page using the Tab key. This is a way of explicitly deciding which element receives the next input from the keyboard. In the past, this was accomplished by giving focus to an element with the mouse or other pointing device and then clicking on the object. The following example sets the second hyperlink to receive focus before the first by setting the second to 1 and the first to 2:

<a href = "http://www.w3.org/" tabindex=2>

<a href = "http ://www.yahoo.com/" tabindex=1>

Ina Nutshell, the W#C model has two basic requirements

The document model can be used to take apart and build the document, even after it is loaded by the browser. Individual elements and their attributes can be added, removed, or changed within the document. This also includes a way to determine and change the content of a page, whether it's text, images, applets, or plug ins. This is the dynamic part.

The DOM won't require a graphical user interface for implementation. This is part of the W3C's goal of providing standards that provides access to Web content for all types of browsers, including those based on Braille and audio technologies.

All other requirements of DOM follow from these two, including each of the major areas required by the DOM working Group

Structure navigation The capability to locate elements in a document, such as the parents or children of an object.

Document Manipulation The standard will provide a way to add, remove, or change elements and tags within the document. This also includes attributes of tags.

Content Manipulation This is the capability to add, change, or delete the content within a document or individual tag.

Event Model The event model is comprehensive enough to generate completely interactive documents. It includes the capability to respond to any user action within the document, including moving in and out of form fields, detecting mouse movements and clicks, and determining individual keystrokes.

Style Sheet Object Model This is similar to Document Manipulation, mentioned earlier. Under DOM, cascading style sheet attributes are also exposed for modification.

General Document and Browser Information The W3C has left no stone unturned. Part of the DOM includes the capability to examine embedded objects such as cookies and the date a document was created. Other information available includes the user agent browser brand and version, and the types of MIME types it supports.

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