Mobile Channels: Take the
Web
With You Wherever You Go
By John Kennedy
Editor's Note: This article was written about the Mobile Channels application found on the
Palm-size PC. Microsoft has recently released
an H/PC version of Mobile Channels, available for free on Microsoft's Windows CE Website.
While a Palm-size PC version of
Pocket Internet Explorer would be nice, most users realize that the small monochrome
screen of the Palm-size PC isn't ideally suited for browsing the Web and viewing Web
pages. The Palm-size PC is an easy-to-use information device, not a miniature desktop
computer.
But there is a lot of very useful and entertaining information on the
Web. Most of it in HTML format, integrating text, graphics, and even sound and movies. Any
Web browser will let you save a Web page in HTML format. Later, when you are off line, you
can view this document with your browser, just like you might view a text document using a
word processor. In a nutshell, this is how Mobile Channels work.
What is a Mobile Channel?
The Mobile Channels application on the Palm-size PC lets you display Web
content you have downloaded to your Palm-size PC from your desktop PC. Most Web pages are
designed to be viewed on a full-sized desktop PC screen. However, some Web sites have a
specially designed "Mobile Channel" site. This involves designing the portion of
the site to be downloaded with the display of the Palm-size PC in mind. It also involves a
number of other things that I'll talk about later on in the article. The "Mobile
Channels" application on the Palm-size PC displays information from one or more of
these "Mobile Channel" sites.
The Mobile Channels concept is a spin-off from the Active Channel
technology built into the desktop-based Internet Explorer 4.0. While Active Channels never
seemed to take off, the Windows CE incarnation could breath new life into the entire
project. Palm-size PCs are not the fastest or easiest systems to use for extensive on-line
browsing, but if you've already identified the Web sites you're interested in, you can
download the Web content to your PC Companion, and have a very quick and portable way to
access the Web content.
Using Mobile Channels
Microsoft implemented Mobile Channels as part of Internet Explorer 4.0
(not any other Web browser). All you have to do is go to a Mobile Channel Web site, click
on a Mobile Channel icon appearing on a web page, and the Mobile Channel portion of that
Web site is downloaded to your desktop PC. The next time you synchronize your Palm-size PC
with your desktop PC, the Web content is copied across ready for you to read from your
Palm-size PC. You can use Internet Explorer 4.0 to make this an automatic process,
specifying which Web content is to be downloaded to your desktop every day.
The first thing you need to do in configure Windows CE Services to
download Mobile Channel data. Make sure the Mobile Channels box is checked in the
ActiveSync Options dialog on your desktop PC. This will ensure that any channels you
select while browsing will be downloaded to your Palm-size PC. That's actually the hardest
part: the rest is easy. Once you have synchronized your Palm-size PC, launch its Mobile
Channels application from the Start menu. Any new Channel will appear on the application's
main screen. To read one you simply tap on the Channel's icon (see Screen 1). The Mobile
Channels application on the Palm-size PC enables you to delete unwanted files, or restrict
the size of any incoming data. The Mobile Channels Options dialog makes this clear (see
Screen 2).
How a Mobile Channel works
A Mobile Channel Web site has a "Channel Definition Format"
(CDF) file that tells a browser accessing it about the scripts, images and HTML files used
in the Web site. The CDF file contains important details about which HTML files are to be
downloaded, the frequency of updates, the icons used in the Mobile Channels home page and
so on. When the user clicks on the Web site's Mobile Channel icon this CDF file, along
with HTML, graphics, and other files, is downloaded by the desktop-based Internet Explorer
browser. When the user synchronizes his or her Palm-size PC, the CDF file and data is
passed on to the Palm-size PC. If you know anything about creating Web pages and Web
sites, creating a Mobile Channel site (or modifying an existing one) is not at all
difficult.
The future of Mobile Channels
I strongly suspect that current uses of Mobile Channels are only
scratching the surface of what's possible with the technology. Using a standard HTML
editor is only one way of creating a Mobile Channel. The Palm-size PC has a complete and
powerful scripting engine built into it: instead of referencing HTML files, the CDF can
point to script files. These files can contain a sub-set of Visual Basic commands to
create some extremely sophisticated displays on the Palm-size PC. For example, it's
possible to use scripts to create custom on-the-fly displays as the Mobile Channel script
accesses and then processes downloaded information.
Furthermore, the display on a Palm-size PC is similar in many ways to
Windows 98's Active Desktop. This makes it possible to build interactive elements into the
Palm-size PC's desktop (like the changing date and time in the taskbar, or the up-coming
appointments displayed in the opening screen). You can see an example of this in Screen 3,
in which my Palm-size PC displays a new "desktop" with a larger time display and
easy-to-use buttons for launching applications.
Finally, Microsoft has recently released a version of Mobile Channels
for existing H/PCs, and rumor has it that it will be built into the new H/PC Pro (see
sidebar above). This should encourage the creation of more Mobile Channel Web sites and
help to kick-start the development of some very powerful and useful new applications.
Screen 1: To read the Mobile Channel information you've downloaded to
your Palm-size PC, open the Mobile Channel application and tap on the icon of the desired
Mobile Channel (Pocket Universe or MSNBC in the above example) to view the information.
Screen 2: You can use the Mobile Channels Options screen on your
Palm-size PC to restrict the size and type of in-coming data, and to clear storage memory
of Mobile Channels content.
Screen 3: Using the Palm-size PC's Mobile Channels scripting language
and Active Desktop, it's possible to re-configure the entire desktop.
Mobile Channel Links
There are dozens of Mobile Channel sites on the Web, ready for you to
access and download to your Palm-size PC. They cover topics including city guides, sports,
news, weather, jokes, Star Trek and programming. In fact, entire books are distributed in
Mobile Channel format. A page of links to Mobile Channel sites is available on Microsoft's
Windows CE Web site, and is located at www.microsoft.com/windows
ce/ppc/channels/featured.asp. A more comprehensive list of Mobile Channel links can be
found on Chris De Herrera's Windows CE Website, located at www. cewindows.net/.
Mobile Channel viewer available for
H/PCs
Microsoft has recently released a Handheld PC version of the Mobile
Channel viewer. H/PC users can now download and view Mobile Channel information
(previously only viewable on Windows CE running on the Palm-size PC).
You can download the H/PC Mobile Channel viewer for free at Microsoft's
Windows CE Web site. The specific Web address is www.microsoft.com/windowsce/down
loads/pccompanions/mcviewer.asp
Mobile Channel Wizard
The Mobile Channel Wizard lets you easily create a Mobile Channel from
any Web site. Simply run the wizard, select or type your URL, choose some options, and
you've created your own Mobile Channel from your favorite Website. Unlike standard mobile
channels, Mobile Channel Wizard channels are not subscriptions and will not be updated
until the Mobile Channel Wizard is re-run on those Web addresses.
You can download the Mobile Channel Wizard for free at Microsoft's
Windows CE Website. The specific Web address is www.microsoft.com/windowsce/downloads/pccompanions/
mcwizard.asp
Screen 4: Use a text editor to create the CDF file for the Mobile
Channel pages you've created. Notice that the code in the CDF file looks very much like
the code in an HTML file.
Creating a Mobile Channel
If you're familiar with creating Web pages and Web sites, creating your
own Mobile Channel is rather straightforward. The key is creating the Channel Definition
Format (CDF) file that tells a browser about the scripts, images and HTML files used in
the Web site. CDF is itself based on the XML language and has much in common with standard
HTML. The content of a CDF file will look familiar to someone used to working with HTML
scripts. Once you've examined a few CDF files to get an idea of their contents and
structure, creating your own should be easy.
Creating the pages used to define the content of the Mobile Channel can
be done using standard Web authoring tools. All the important HTML tags are supported,
although you won't be able to use fancy fonts and animated GIF files. And you should
design your screens (and test them) to make sure they display well on the Palm-size PC's
320 by 240, four gray-scale screen.
It's also vital to keep your file sizes down. This minimizes downloading
and transfer times. It's also important because the Palm-size PC stores Mobile Channel
data in main memory, rather than on a PC storage card. While there are ways around this
restriction, there are disadvantages associated it. It's something for advanced users
only.
Creating Sticky Software's Mobile Channel
My company maintains a Web site for the Windows CE software we have
developed, including a program called Pocket Universe, which displays a sky map of stars
and planets on the Palm-size PC (contact Sticky Software at http://www.sticky.net). I wanted to add a Mobile Channel
to our site to provide Palm-size PC users with some more Pocket Universe information in an
easy-to-access format. Although it would be possible to provide the data (dates of meteor
showers, bright star clusters and so on) in help-file format, a Mobile Channel is easier
for users to download and install. It's also easier for me to update and has the benefit
that visitors to the Web site who don't currently own the application can still download
and browse the channel.
Here are the steps I followed to create the Mobile Channel.
Step 1: Write the Mobile Channel pages
of information
This is probably the hardest part of the process. I used FrontPage
Express, which comes with Windows 98. Keep in mind that the design must take into account
the Palm-size PC's small screen and limited graphics capabilities. There will be no large
graphics in these pages, just useful text.
Step 2: Create the Mobile Channel CDF file
After creating the HTML pages and a small menu page, the next stage was
to write the CDF "wrapper" which tells the browser accessing the site about the
Mobile Channel part of the site (see Screen 4). This took a bit of figuring out, mostly
from looking at other Mobile Channels and referring to the information on the Microsoft
Website. The CDF file is a simple text file and Notepad was the easiest way to create the
file.
Step 3: Add the Mobile Channel files to the Web site
Once tested, all the files used in the channel can then be uploaded to
the Website (see Screen 5). A standard graphic image is used to provide a link to the CDF
file, allowing visitors to click and download the Mobile Channel data to their PCs, ready
for transfer to the Palm-size PC at the next synchronization.
Step 4: Download the Mobile Channel to your Palm-size PC
Synchronize your Palm-size PC with your desktop PC, automatically
downloading the Mobile Channel data to the Palm-size PC (see Screen 6). The new Mobile
Channel provides an easy way of supplementing the product's on-line help with useful data
which the user can reference at any time. Best of all, anyone can download the channel
without first buying the application.
If you plan on creating your own Mobile Channel, check out Microsoft's
Mobile Channels Development Kit Preview Release pages at www.microsoft.com/
workshop/delivery/mobile/mcdk_in.asp. You might also find the Microsoft CDF file
utility useful (www.micro
soft.com/gallery/ tools/liburnia/liburnia.asp).
Screen 5: Once you've created and tested the necessary files, upload
them to your Web site. A standard button labelled "Add Mobile Channel" links to
the CDF file. Visitors click on the button and download the Mobile Channel data to their
PCs.
Screen 6: Sticky Software's Pocket Universe Mobile Channel provides
supplementary information about the product to Palm-size PC users.
|
 By John Kennedy
John Kennedy is a technical journalist based in Northern Ireland (although
he's open to offers). When he's not writing, he's programming Windows CE applications for
Sticky Software. E-mail: johntkennedy@sticky.net.
|