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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
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.
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WML
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 <WML> is different
from <wml>
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.
I hope that you've enjoyed it thus far,
Pete
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