XHTML standards development Web Designing

Things are exciting over at the W3C. Now that they have XML on theirtoolbelts, they seem to be on a roll in rethinking and reshaping document markup. Between January 2000 and June 2001, they have turned out three XHTML Recommendations: XHTML 1.0, XHTML Basic, and XHTML 1.1 (XHTML 1.1 is still "Proposed" as of this writing, but since it's on the verge of approval, I'll count it anyway). This section looks at each one.

The XHTML 1.0 Recommendation (released in January 2000) is really just areformulation of the HTML 4.01 specification according to the rules of XML.

Like HTML 4, XHTML 1.0 comes in three varieties -- Strict, Transitional, andFrames -- each defined by a separate DTD.

It is important to specify which version you are using in your document, as modern browsers (IE 5.5+ and Netscape 6) can use this information to turn on "strict" standards-compliant formatting, as opposed to the "quirky" behavior of older, nonstandard HTML. Of course, if you do specify the DTD, then you must stick to it exactly so that your document will be valid (i.e., not breaking any rules defined by the DTD).

You must also make sure to specify the proper namespace declaration for XHTML.

Strict DTD
This version excludes all deprecated tags and attributes (like <font> and align) to reinforce the separation of document structure from presentation. All style information is delegated to Cascading Style Sheets, which work the same in XHTML as in HTML.

While it is certainly possible to begin constructing web pages and sitesaccording to the Strict DTD, it poses a greater challenge. Because there are still millions of web users with older browsers that don't support style sheets and HTML 4.0, you run the risk of alienating some users (or providing them with only lowest common denominator content). Fortunately, there is evidence that things will get easier in the future. The latest round of major browsers (Internet Explorer 5.5 for Windows, Internet Explorer 5.0 for Macintosh, andNetscape 6 on all platforms) snap into perfect standards-compliance mode when you specify "strict" in the DOCTYPE declaration.

Transitional DTD
The Transitional DTD includes all the deprecated elements in order to cater to the legacy behavior of most browsers. Deprecated tags and elements are permitted but discouraged from use. This DTD provides a way to ease web authors out of their current habits and toward abiding by standards. Most web authors today choose to use the Transitional DTD since it is what works best in most browsers.

Frameset DTD
This specification is exactly the same as the Transitional DTD, except that it includes the elements for creating framed web pages (<frameset>, <frame>, and <noframe>). The Frameset DTD is kept separate because the structure of a framed document (where <frameset> replaces <body>) is fundamentally different from regular HTML documents.

The XHTML Basic Recommendation (released in December 2000) is a stripped-down version of XHTML 1.0 aimed at preparing documents for mobileapplications such as cell phones or handheld devices. The specification is
consistent with the XHTML modularization efforts (discussed next). XHTMLBasic contains the minimum elements necessary to be considered an XHTML document, plus images, forms, basic tables, and object support.

XHTML 1.1 (Modular XHTML)
XHTML 1.1 (a proposed recommendation as of this writing) reflects abreakthrough in the way markup languages are constructed. Instead of one comprehensive set of elements, this specification is broken up into task-specific modules. A module is a set of elements that handle one aspect or type of object in a document. Some modules include the core module, text, forms, tables, images, imagemaps, objects, and frames.

In a world where HTML content is being used on devices as varied as cellphones, desktop computers, refrigerator panels, dashboard consoles, andmore, a "one-size-fitsall" content markup language will no longer work.Modularization is the solution to this problem. This recent module approach has a number of benefits:

  • Special devices and applications can "mix and match" modules based on their requirements and restraints. For instance, a simple refrigeratorconsole probably doesn't need applet and multimedia support (although, who knows?). With XHTML 1.1, you can create a document that uses only the subset of XHTML that meets your needs.
  • It prevents spin-off, device-specific HTML versions. Authors can create their own XML modules, leaving the XHTML standard unscathed.
  • It allows "hybrid" documents in which several DTDs are used incombination. For instance, it allows web documents to have SVG(Scalable Vector Graphics) modules or MathML modules mixed in with the XHTML content.

Modularization is the way of the future for markup standards. The SMIL 2.0 specification is also broken into modules, which can then be used with other languages like XHTML.

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