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WAP and WML The Wireless Application Protocol

WAP architecture
WML document structure
WML syntax

•Basic document syntax•Layout•Text formatting•Images•Navigation•Events•Variables

WAP and WML

WAP Architecture ^

Do you still need a web server?^

Early WAP server designs included an HTML-to-WMLconverter. The theory was that you could serve your originalcontent, just reformulate the tags into WML in an automatedmanner. Your web server became a back end behind yourWAP server; the WAP server would translate requests fromthe Gateway, through to the web server, and back.
^

This failed painfully.

It’s clear now that your content needs to

either be in WML, or you need to design for a one-inch-squarescreen in your HTML.

So, if not a web server, then--?^

Your WAP server

is

the web server.

^

You can serve both types of content from one system.

WAP Architecture ^

Follow the request:^

Client establishes a data connection to WAP Gateway
^

Client sends WTAI (“

Wireless Telephony Application

Interface

”--HTTP for phones) request for URL entered

^

WAP Gateway receives request, decodes it
^

WAP Gateway sends HTTP request to Web Server
^

Web Server replies with content
^

WAP Gateway re-encodes content and sends it back to client
^

Client renders content locally

WML Syntax ^

^

^

^

title=“…”
^

id =“…”
^

newcontext =“true”, “false”
^

onenterbackward =“[url]”
^

onenterforward =“[url]”
^

ontimer =“[url]”

WML Syntax - Layout ^

^

align=“left”, “right”, center”
^

mode=“wrap”, “nowrap”

^

columns=“…”
^

align=“l”, “c”, “r”
^

^

Cell 1Cell 2Cell 3

WML Syntax - Images ^

- Render a WBMP file^

src=“…”
^

align = “top”, “middle”, “bottom”
^

alt=“…”
^

height=“…”, width=“…”
^

hspace=“…”, vspace=“…”

An image:

WML Syntax - Navigation ^

As in HTML, you link from page to page explicitlywith

anchors

This is a link



WML offers the tag and the tag

- the simple anchor tag^

href=“…”

- more powerful anchor tag^

, , , , ...

WML Syntax - Navigation ^

- Navigate to a new card

- Back up one on the card stack

- Reloads the current page

- Do nothing

- Sets a variable

- Sends a

post

(or

get

) field value to

the server

WML Syntax - Events ^

is the softkey event handler.

is a more generalised events handler.^

type=“onenterbackward”, “onenterforward”, “onpick”, “ontimer”

Use onevent to process data differentlydepending on the action of the user.

For example, you might want to initialise avariable to zero with onenterforward, but thenincremement it to track user returns inonenterback. Onenterback will fire whenever theuser uses the

prev

softkey to return to the page.

WML Syntax - Variables ^

A

variable

in a WML script is a data field whose

value can be changed before the next update.

This is a divergence from HTML.

HTML does not

have the concept of variables, because HTMLhas inline JavaScript instead.

Variable names, like all concepts in XML, arecase-sensitive.

To refer to a variable in your code, use a dollarsign ($) followed by the name of the variable,optionally enclosed in parentheses.^

$foo
^

$(foo)

WML Syntax - Variables ^

Variables are set with the tag.

Variables, once set, take effect when the page isnext reloaded. Unfortunately, since runs when an event triggers it, you can’t initialisevariables cleanly.^

WAP and WML - Recap ^

WAP architecture^

Client, WAP Gateway, Web Server

WML document structure^

DTDs, decks and ’s

WML syntax^

Basic document syntax - , , ...
^

Layout -

, ,

, ...
^

Text formatting - , , , , , ...
^

Images - - WBMPs only.
^

Navigation - , ,
^

Events - ontimer, onenterforward, onenterbackward, ...
^

Variables - , , $(foo)

WAP and WML - Bibliography ^

WAP in Easy Steps, by Mike McGrath. (C)2000 published by ComputerStep, Warwickshire



http://www.w3schools.com/wap/wml_reference.asp

• a

really well-done WML reference



http://developer.openwave.com/

• OpenWave are the folks

who’re defining the WAP gateway standards. They alsomake a mobile device SDK.



http://www.openmobilealliance.org/documents.html

Technical specifications page for the Open Mobile Alliance,the public body which binds the many corporationsinvesting in WAP and related technologies.

Note: site can

be a bit thick