Intranet Journal - The End of Software Vendors' Absolute Reign

Page II

XHTML: The Transition From HTML to XML

The Cornerstone of a Portable, Modular Language
XHTML 1.0's technical innovations are only minor. However, by rendering HTML compatible with XML, this slight technical evolution provides the basis on which to build a portable (especially in terms of WAP technologies) standard that will function in a modular manner. Indeed, XHTML 1.1, the version on which the W3C is currently working, is designed to break HTML up into different modules, each of which is made up of a subgroup of HTML tags. The principal modules are as follows:

The structure module defines document structure.
Related Tags: <body>, <div>, <head>, <html>, <span>, <title>

The hypertext module defines hypertext link management.
Related Tags: <a href>

The basic text module is made up of the basic text presentation tags.
Related Tags: <h1>...<h6>, <p>, <pre>, <br>, <em>, <strong>

The list module defines list use.
Related Tags: <dl>, <ol>, <ul>, <li>

The above modules are the ones a document needs in order to be considered part of the XHTML family. The following secondary modules can be added depending on an application's needs and the functionality supported by the device in question:

Other XHTML modules defined by W3C (for images, forms, scripts, applets and so on).
Customized modules created by the developer. As is the case with XML, these modules must also match a DTD. TOP

Integrating This New Standard

If you have to develop a Web site and you already know HTML 4, you will have no problem writing XHTML 1.0 documents. There are just a few syntactic rules to apply so as to ensure XML compatibility. You have two different solutions if you want to migrate HTML pages to XHTML. You can either apply the below rules manually or use available tools designed to convert documents (presented later in the document).

Writing an XHTML 1.0 Document
More Rigorous Syntax

Unlike HTML, an XHTML 1.0 document must be extremely well-formed, which can be defined by the following rules:

Rule #1: All XHTML tags are included in the <html> root tag and must be well-structured. For example:

<html>
<head>...</head>
<body>...<body>
</html>

Rule #2: Since XML is case-sensitive, all names, tags and attributes must be written in lowercase letters.

HTML 4.0	XHTML 1.0
<TD BGCOLOR="#ffcc33">	<td bgcolor="#ffcc33">

Note: Attribute values can be written in lowercase or capital letters. For example, the bgcolor attribute values "#ffcc33" and #FFCC33" are equivalent.

Rule #3: · Any tags that are not empty must be closed systematically.

HTML 4.0	XHTML 1.0
Paragraph 1<p> Paragraph 2<p>	<p>Paragraph 1</p> <p>Paragraph 2</p>

Rule #4: Empty tags must finish with a slash (/).

HTML 4.0	XHTML 1.0
<input...> <img src="image1.gif">	<input.../> <img src="image1.gif"/>

Rule #5: Overlapping tags are no longer authorized.

HTML 4.0	XHTML 1.0
<b><i>bold and italic</b></i>	<b><i>bold and italic</i></b>

Rule #6: All attribute values must be placed between quotation marks (for example, <table... border="0">) and they can no longer be abbreviated.

HTML 4.0	XHTML 1.0
<input type="radio"...checked>	<input type="radio"... checked="checked">

Rule #7: The <script> and <style> tags must contain a CDATA section. In XML, this section, which is delimited by the <![CDATA[ and ]] > tags, indicates that the information between these tags is data and does not need to be parsed.

HTML 4.0	XHTML 1.0
<script language="JavaScript"> <!-- document.write("Hello World!"); //--></script>	<script language="JavaScript"> <!-- <![CDATA[ document.write("Hello World!"); ]]> //--> </script>

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TechMetrix Research is a technically focused analyst firm focused on e-business application development needs. Based in Boston, Mass., the firm publishes comparison reports and product reviews designed to aid enterprises with decision making and to keep pace with the fast-moving e-business market.

TechMetrix is a U.S.-based subsidiary of SQLI, a European company that offers on-site development services to international organizations. SQLI specializes in e-business project development.