Mobile Markup Languages: WML and XHTML MP
Having already known the technical standards that guide mobile web designers, it’s important to focus on the two mentioned markup languages: WML and XHTML MP.
Lets start with their similarities. They’re both based on XML, and they were both developed with the mobile web in mind. That’s pretty much where their similarities end.
WML, is the markup language created by the Open Mobile Alliance. It predates the more advanced XHTML MP in mobile web markup languages. WML documents are XML documents that validate against the WML DTD (Document type Definition). Like HTML, it provides support for navigation, data input, hyperlinks, text and image presentation, and forms. A WML document is called a deck, which is composed of one or more “cards,��? which are what will users see as pages. Each card represents a single interaction with the user. To control navigation among the cards, WML supports a scaled-down procedural elements (do, onevent, postfield).
The main design principle with WML is to support the limited mobile web device browsers. Since most modern mobile web browsers and almost all old WAP-enabled ones will properly render a WML document, a WML-implemented design is accessible even to the most limited mobile web devices.
XHTML on the other hand is the extension of HTML that enforces the strict syntax checking of XML, and XHTML MP (Mobile profile) variant is a subset that addresses some of the constraints of the mobile device browsers. The XHTML standard was started by W3C independent from the Open Mobile Alliance. With XTHML MP, the power of the CSS has been brought to the mobile web. This is what makes XHTML MP a more powerful and designer-friendly competitor to the aging WML.