Creating Web Pages For Phones, PDA’s and Beepers
Wireless devices, like the new phones, PDA’s and smart pagers, are growing in number as people may want to get information immediately no matter where they are. They may want: to check the weather, find a good restaurant, get directions to a movie theater, stock quotes and similar things like airline information. As useful and as popular as these devices are getting, there are a few considerations that need to be addressed that you don’t have to worry about when making regular websites.
Most of these “considerations” have to do with the fact that the thing is just so dagone small. It has small screens, little memory and CPU power and browsers which can’t be too big. Additionally, they have low bandwidth problems. This all adds up to us as the code writers/developers having to be really strict with our code so that the browsers don’t have to do too much interpretations of what you mean and can handle it. However we do need to know a couple of those dragonet acronyms, WAP and WML.
WAP stands for Wireless Application Protocol. A protocol is a set of rules which devices and developers need to follow in order to communicate with other similarly enabled systems or devices. In other words, they all need to follow the same rules in order to play the game. There are over 100 different protocols and WAP, a new one, was created for the wireless world. WAP was adopted by the leading body of this industry, the WAP Forum. The WAP Forum was started by some of the biggies of the phone world: Motorola, Nokia, Ericsson, and Unwired Planet. Therefore, a lot of the devices made by these companies are configured to work with this protocol. However, WAP, being an open standard and is network-independent, can work on top of any wireless protocols.
From a webmasters point of view, the WAP device has an IP address just like a laptop or a PC and sends information through the regular HTTP requests. However, the difference is that there is a WAP gateway between the server and the device which translates the code into a binary format (machine code) which makes it much lighter data when sending and receiving. The web server nor the receiving device knows, nor needs to know, anything about this gateway.
WML stands for Wireless Markup Language. It is very similar to both, HTML and XML so if you know HTML, you’ll have a easy learning curve with this language. I did want to mention that WML is the present language used advocated by the WAP Forum but they are moving toward using XHTML in their next generation WAP 2.0, also known as WAP NG with the “NG” standing for Next Generation. WML, like XHTML, is a bit stricter than HTML, so we don’t have the option of forgetting about ending tags and stuff like that. So how’s the language work?
Firstly, when you save the page, it is saved with an .wml extension instead of the .html one that we use with regular web pages.
Secondly, since making it as light as possible is the goal. WML documents are mostly about text with a few tags which correspond to our regular html tags.
Thirdly, in adopting policy from XML, which it is a part of, everything is case sensitive. So
Fourth, we must have an ending tag for ALL our WML tags.
Now, when creating these pages, the popular analogy is to see the document(s) as a set of regular playing cards. In fact each little page that appears in the devices little browser is called a “card” and the entire .wml document is called a “deck”. A deck as we mentioned earlier contains cards. Additionally, decks can also contain text, links, images, input fields etc. Furthermore, cards can be linked to each other. When the page is called by an Internet phone’s browser, the entire deck is downloaded so that you can quickly navigate between cards.
It would be best to see this analogy with a deck of cards facing you. You can see the top one and when you navigate to another card the browser quickly looks it up and displays it. By the wireless browser downloading the entire deck, the user doesn’t have to worry about “latency” which is the amount of time the physical device takes to send and get information from the server.
In next weeks issue of DevWebPro, I’ll go over examples of .wml which will help clarify how several of the tags are used.
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