A wireless rationale for XHTML
Ed Tittel
As regular readers of my tips know, I've been arguing for switching Web sites over from HTML to XHTML, both here and in my tips for www.SearchWebHosting.com. Recently, I responded to a question from a reader who led me into another great reason for considering--and making--this move. In a word, that reason is wireless.
A Motorola employee, this reader wrote me as follows during the week of March 26: "Cell phone makers recently agreed to adopt XHTML as their standard of choice for cellular content delivery.
- How does XHTML extend or compete against WAP?
- How does XHTML extend or compete againstWML?
- How does XHTML extend or compete against cHTML?
- How does XHTML extend or compete against iMode?"
This turns our to be a very interesting set of questions, that all add up to a strong justification for XHTML. First let me identify each of these other initiatives, and also explain how they relate to XHTML.
WAP (Wireless Application Protocol)
WAP is a communications protocol and an application environment designed to work through wireless networks. It emerges from the WAP Forum and is not a part of the W3C or IETF standards tracks. Most experts agree that the majority of new wireless devices will be WAP-enabled by the end of 2001, if not sooner. WAP is vying for part of the same position in providing data to wireless devices that XHTML is, in that it provides a way to encapsulate and mark up content for delivery to wireless devices. I don't see this as a "killer form of competition" however, because XHTML's ability to work with XSLT means that you could store data in XHTML format or create XHTML on the fly, then use XSLT to transform it into WAP for final delivery. The formatting/content container portion of WAP is the Wireless Markup Language, or WML. There's a great WebReview article on WAP that also talks about i-Mode.
WML (Wireless Markup Language)
This is the wireless markup language that WAP uses to encode content for delivery to wireless devices. As such, the combination of WAP and WML is a complete way to move, markup, and display data on wireless devices. It competes head to head with XHTML plus whatever protocols might be in use to carry XHTML from a Web server to a wireless device or vice-versa. Best place to go for more information on this topic is the O'Reilly WML book: Learning WML & WMLScript: Programming the Wireless Web, By Martin Frost, published by O'Reilly & Associates. But here again, I see this as a complementary technology that would apply only in the final server-to-device link, after XHTML has already done its thing as explained in the preceding paragraph.
cHTML (compact HTML)
cHTML is a compact variety of HTML that is to i-Mode as WML is to WAP. In other words, cHTML provides a mechanism to capture and represent data and content for delivery to i-Mode clients, and i-Mode provides the underlying protocol and message services necessary to reach them to receive data, and to listen to them so they can send data. As with the WAP/WML combination, though you might be tempted to see this as directly competitive, I do not see this as a "killer form of competition" either because XHTML could use a different XSLT transform to deliver its original content and data to a cHTML/-Mode consumer, just as it can use another XSLT transform to do the same thing for a WML/WAP consumer. A great article on cHTML and i-Mode by Didier Martin for XML.com is available at http://www.xml.com/pub/a/2000/09/20/wireless/imode.html.
i-Mode
According to Didier Martin, i-Mode is akin to a brand name that represents numerous services and capabilities like AOL or Yahoo! than it is like a single protocol/service combination that you might be familiar with from the Internet (think FTP, telnet, network news, and so forth, all of which represent both specific services and the protocol and its associated message formats used to support that service). i-Mode is more sophisticated than WAP, and supports 256 colors, and can even render .gif graphics (which WAP cannot currently handle). Be sure to check Didier's article mentioned in the preceding paragraph for some links to the W3C submission on cHTML, an i-Mode markup reference, and i-Mode Resource center. Good stuff!
Thus, here's the best explanation, to me, of why XHTML was selected by the cellular phone vendors as their markup language of choice: They know the underlying XML infrastructure (especially XSLT) that supports XHTML makes it easy to choose a single markup language that can be transformed to support either or both of the leading contenders for wireless devices at present. XHTML also remains flexible enough by design to support other new contenders as they emerge (and they will, as sure as there's more than one new generation of wireless devices still left in our future). Because it closes no doors, and is capable of handling multiple "final link" formats, XHTML makes a lot of sense for wireless applications, and for other special-delivery mechanisms.
Contact Ed at tips@searchmiddleware.com if you have questions on this or other XML topics.
Ed Tittel is a principal at LANWrights, Inc., a wholly owned subsidiary of LeapIt.com. LANWrights offers training, writing, and consulting services on Internet, networking, and Web topics (including XML and XHTML), plus various IT certifications (Microsoft, Sun/Java, and Prosoft/CIW).
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