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HTML 4.0 unwrapped
By Mark Gibbs Now in its 4.0 release, HTML has come far from its roots as a quick hack Tim Berners-Lee wrote for use with the World Wide Web he invented back in 1989. Berners-Lee based HTML on the Standardized General Markup Language, a full-blooded International Standards Organization standard, but his interpretation was rather loose. The World Wide Web Consortium (W3C) ended up adopting HTML, and released the latest iteration in December 1997. HTML 4.0 builds on Version 3.2, its predecessor, by adding new elements, deprecating some elements and obsoleting a few others. The W3C considers deprecated elements as outdated, but vendors must support them for compatibility with earlier products. These elements probably will become obsolete in the future.
Best BitsAmong HTML 4.0's highlights is support for sophisticated buttons. The new <button> element has a type attribute (submit, reset or button) and its content may be an image. For example, the following specification creates a button with text overlaying an image: <button type=button><img src= "connect.gif">Connect</button>. Prior to HTML 4.0, browsers interpreted table-caption alignment with wild abandon. Now the align attribute for the position of table captions defines values of top, bottom, left and right. There's also support for building table cells from right to left for languages written that way. The new <thead>, <tfoot> and <tbody> elements enable grouping of table contents. Each table can only have one header and one footer section but multiple body sections, making it easy to structure table contents. For example, you can apply alignment attributes to sections so that all rows within a section are targeted. Similarly, the new <colgroup> element supports grouping of columns. Again, alignment attributes apply to all columns within a group. Forms acquire grouping with the <fieldset> element. As with the table row and column grouping functions, <fieldset> alignment attributes apply to all fields in the group. You can name fieldsets with the <legend> element, which has an alignment attribute for controlling where the label appears relative to the fieldset. An addition to form elements is the "taborder" attribute. This attribute is for controlling the tabbing order of the fields. All fields with a tab order of one or higher are followed in sequence; fields without a specified tab order or a tab order of zero are followed in the order that they appear in the HTML code. Tabbing makes keyboard access for controlling the user interface accelerator keys easier. For example, you can associate Alt R with a reset button by using this code: <button accesskey="R" type= reset> Reset</button>. Accelerator keys apply to the <a>, <area>, <button>, <input>, <label>, <legend> and <textarea> elements. However, HTML 4.0 doesn't define how the user will be alerted that an accelerator key exists. That's left to the browser vendor. HTML 4.0 also spruces up event-handling capabilities. Under this version, almost any element can respond to a set of element event handlers. The events now recognized are:
These events would typically be associated with JavaScript code. Lastly, HTML 4.0 introduces the <object> element. This <applet> replacement offers a generic way of specifying images (rather than using the <img> element) and in-line frame specification (the <iframe> element). The <object> element allows control of whether data should be rendered by an external program or within the document by an author-specified application. In general, the object element requires three specifications: the implementation of the included object (the location of executable code), the data to be rendered and additional values required by the object at run-time (such as initial values for parameters). One of the powerful object features is the ability to specify alternate renderings. You could write code, specifying, for example, that an applet written in the Python language be used and failing that, then an MPEG video, a GIF image and, finally, a plain text rendition.
Future ContentWhat does HTML 4.0 mean to intranet and extranet managers? The standard will go a long way toward stopping the explosion of proprietary HTML extensions, but it doesn't make much impact resolving compatibility issues between the Microsoft and Netscape implementations of "dynamic" HTML. This is because each browser handles the Document Object Model (DOM), the document architecture the W3C is working on, differently. The DOM defines standard interfaces between browser events, style sheets and scripts. HTML 4.0 will supplement the DOM, but that's about as far as the specification is expected to go. In April, participants at a W3C HTML workshop decided that extending HTML would be difficult. Instead, they propose starting fresh with the next-generation HTML by using a suite of Extensible Markup Language (XML) tag sets. In effect, they espouse creating a modularized HTML. Their view is that modularized HTML will be more manageable and easier to integrate with other XML tag sets. But never fear. The reality for intranets and extranets is that the stability of existing HTML content is assured for years to come - browser vendors will always make their new versions backwards-compatible. Most browser and authoring tool vendors won't support the full HTML 4.0 feature set until the end of 1998 at the earliest, but you might want to start polishing existing content and ensuring that new content is HTML 4.0-compatible anyway. When you begin doing so, check out the W3C's validation service as a handy reference point. |
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