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trip report from the ninth World Wide Web conference in amsterdam, the netherlandstutorial 5: wireless application protocol (WAP) |
home - introduction - WML script - implementation recommendations - roadmap - WAP forum - my comment
author: don schuerholz, manager of developer services at phone.com inc.
number of attendees: approx. 80
don started the tutorial with a short introduction to WML and presented its main features. he explained the basic syntax rules, such as:
- the tags are case sensitive and must be written in lower case
- all attributes must be enclosed in double quotes, e.g. <input name="currency">
- tags which have no separate closing tag must have a slash before the closing bracket, e.g. <br/>
he also mentioned that the maximum size of a WML-deck is approximately 1500 bytes.
don did not go into much details about WML script. he said it is mainly used for input validation, but may be used for other purposes, such as implementing a calculator, a currency converter or even a simple game.
However, there is an important security issue which programmers should be aware of:
there is only ONE GLOBAL name space for WML variables !Therefore:
- make sure you initialize your variables and do not rely on any preset values
- make sure you erase sensitive data when your application is done
currently, there are two major WML browser implementations available, one from phone.com and one from nokia. phone.com has written a design guide which should help developers to write portable code which should work with both browsers. at the same time, phone.com has developed some extensions to WML which work only on their WML browser. the design guide plus other technical information is available from developer.phone.com (access is free, but one has to register itself first).
due to the limited size of today's WAP capable phones, don made the following suggestions:
- assume a screen size of 3x12 characters
- do not use words with more than 12 characters, because not all phones support horizontal scrolling yet (longer words may get truncated)
- softkey labels should not be longer than five characters
- use localsrc (icons stored in the phone-browser's memory, unfortunately not yet standardized) to preserve bandwidth
- provide a list of items to select from rather than an input field whenever possible - it is much more convenient for the user
- if you use item lists, make sure the items which will be selected more frequently (or which you consider most important) are listed on the top
- if you have to use an input field, use the format attribute as a hint for the user so she or he knows, what type of data is expected (numeric, alpha or alpha-numeric) and maybe even how many digits or characters are required
- if possible, use numbers rather than letters for input, it is much easier to enter numbers. consider assigning a PIN number to your users rather than a username.
- use one card per input element - put multiple input elements in a series of cards and use the softkey label on the last card to indicate when all data has been entered so that the real action can be started (e.g. "Search", "Buy" etc.)
- submit all data at once to reduce latency (GSM is a SLOW network !)
- WAP V1.2: mainly bug fixes, will add the push protocol (PAP), vendor implementations will become available this year
- WAP V2.0: under development, WML convergence with basic XHTML
- further issue: off-line capabilities, it should be possible to download multiple emails at once and read them later, even if there is no connectivity, e.g. in an underground train etc. (one of the main problems is the limited memory capacity of the current phones)
a number if companies have formed the WAP forum. at www.wapforum.org, you will find:
- WAP specifications
- an application certification program
- membership registration
this was a good overview of the features of WML. however, from a content provider's point of view, it is bad news that we have a somewhat similar situation like a few years ago, when we had two major HTML browsers with different capabilities (remember "the browser war" ?). again, a WML developer must test her or his application with various browsers to make sure it works with most of the WAP enabled phones available on the market today.
still, don's recommendations seem very reasonable to me and i will test our WAP applications to make sure they work with both browsers. see wap.ethz.ch if you have a WAP browser or a WAP phone or http://wap.ethz.ch/www/ for information about our WAP based services in HTML.
this trip report was written on a Vadem Clio C-1050 running Windows CE with Pocket Word. It was then transferred to a DELL Latitude notebook and modified as needed. this document is supposed to be HTML V4.0 compliant.