Page 47 - DCAP512_WAP_AND_WML

Unit 4: Introduction to WML

4.1 What is WML? Notes

WML is an acronym for Wireless Markup Language. While the HTML language creates web
pages for the PCs, the WML creates web pages for the handheld devices. WML’s similarity to
HTML was not random. The structure, formatting, and syntax are immediately recognizable to
those familiar with HTML and XML. WML is a direct descendent of Handheld Device Markup
Language (HDML). WML, however, has been optimized for the constraint wireless device. As a
result, there is a prominent difference between HTML and WML.

Wireless Markup Language (WML), based on XML, is a markup language intended for devices
that implement the Wireless Application Protocol (WAP) specification, such as mobile phones.
It provides navigational support, data input, hyperlinks, text and image presentation, and forms,
much like HTML (HyperText Markup Language). It preceded the use of other markup languages
now used with WAP, such as HTML itself, and XHTML (which are gaining in popularity as
processing power in mobile devices increases).
WML is a markup language designed especially for specifying and displaying content on WAP
(Wireless Application Protocol) devices. WML is part of the WAP application environment,
which requires the use of WML.
WML is the wireless equivalent of HTML for the Web. WML is based on XML and derived from
xHTML (the XML version of HTML). There are many differences between WML and HTML. For
example, WML has a different mechanism for linking between its pages called “cards” as
compared to linking between HTML pages. WML browsers are stricter than HTML browsers by
not being tolerant of errors. WML browsers enforce the WML requirement of matching closing
“tags”, an XML characteristic.

Did u know? What are the limited capabilities of WAP devices?
WML works with the WAP micro browsers found on WAP devices. This browser is
cognizant of the limited capabilities of WAP devices such as
 small displays,
 limited processing power,

 limited memory,
 narrow bandwidth connection, and
 limited battery use without recharging.
To address the limitations of WAP devices, WML uses the metaphor of card decks, and each page
is referred to as a card. The card is the basic unit of navigation and user interface. The user can
view only card at a time. WML browsers read the whole deck (complete document) from the
server to minimize interaction with the server. Consequently, when flipping (navigating)
between the cards in a deck, the browser does not contact the server. This eliminates delays
(because each card contains very little text and users are likely to move quickly from one card to
another).

A WAP deck is the equivalent of a Web page, the card being the portion of the Web page that can
be seen on the screen. Navigation within the cards of a deck is done within the WAP device just as
scrolling a Web page is done within the Web device. (Without contacting servers in both cases).
An HTML writer does not worry about screen or display boundaries. Instead, the Web browser
manages issues relating to the screen boundaries. But a WML writer must be aware of screen
boundaries of WAP devices when writing code for cards.

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