BlackBerry Development : Pushing Data to External Users - Web Signals (part 1) - How Web Signals Work

9/21/2013 3:32:28 AM
Web Signals is a service that provides organizations with the ability to push a URL for a target web page and two icons (a read icon and an unread icon) to a BlackBerry device. This is similar to the way Browser Channels work, but a limited version. With Browser Channels, developers have control over many of the options for the channel, but Web Signals can only push a URL and two icons to the destination device—nothing more. Where an application uses HTTP headers to deliver a Browser Channel parameters to a device, with Web Signals, it’s done through parameters included in the push URL.

In practical use, a developer is likely not going to change the URL being pushed to a subscriber. If the Web Signal is architected correctly, the information that the backend system needs to render the correct information for the subscriber should be built into the URL. Rather than sending a custom URL with every push, craft the URL carefully (with all the information needed to generate custom content for the subscriber), and then just generate the content as needed on the backend, leaving the URL static. In this case, subsequent push requests merely notify the user that there is new data available for the Web Signal. The Web Signal can send different icons periodically, but it would likely not push a different URL every time.

Some examples of how this technology could be used are

  • Weather: An organization providing weather forecasts could build a Web Signal and periodically push a weather icon to subscribers. The signal’s icon would show graphically what the current weather conditions are for the registered location.

  • Stocks: A financial management service could create a Web Signal that allowed a subscriber to register for the stocks they were interested in monitoring. It would deliver an icon that indicated by color or some other mechanism (such as a plus/minus or up/down arrow), indicating the current value of the stock being monitored.

  • News: A news aggregator service could offer a Web Signal that allowed subscribers to define search terms they were interested in. The Web Signal would push an alert when any related items were published online. The icon for the Web Signal could be just the icon for the news service or could indicate visually for example the priority of the items in the current update (high, medium, or low, based on source or date).

To see a listing of the available Web Signals, go to RIM’s Web Signals website at Figure 1 shows the site.

Figure 1. BlackBerry Web Signals website

1. How Web Signals Work

This section uses one of the public Web Signals to demonstrate how a Web Signal works from the end user’s perspective. Subsequent sections discuss how each step would be performed by a push application.

The first Web Signal announced by RIM was a free weather service provided by AccuWeather ( Subscribers register for the Web Signal and identify the location for which they are interested in receiving weather reports. Figure 2 shows the AccuWeather Web Signals page.

Figure 2. AccuWeather Web Signals page

To register for the Web Signal, the subscriber must access the signal’s registration page at from a BlackBerry device. Because Web Signals push data using the BIS service rather than the BES, the Internet browser must be used to access the registration site. On the site, the first thing the subscriber sees is a page describing the service and a link for them to use to subscribe to the service, as shown in Figure 3.

Figure 3. AccuWeather Web Signals information page

The subscriber is presented with information about the service and might need to agree to the terms and conditions for the service before he can continue. After the user indicates that he wants to use the service, he is directed to the RIM’s website, where he must agree to RIM’s terms, as shown in Figure 4.

Figure 4. BlackBerry Web Signals service agreement page

After the subscriber accepts RIM’s agreement, he is directed to a page where he can configure the location for which he will receive weather alerts, as shown in Figure 5.

Figure 5. AccuWeather Web Signals preferences page

Some time after you complete the registration process, the first weather Web Signal is delivered to the device, as shown in Figure 6.

Figure 6. AccuWeather Web Signals icon

The AccuWeather icon is highlighted in the figure. The icon indicates that snow flurries are currently falling and the title of the Web Signal (shown at the bottom of the screen) indicates that the projected high temperature is 23 degrees and the projected low is 10 degrees.

When the Web Signal is opened, the browser opens and displays the weather report for the specified location, as shown in Figure 7.

Figure 7. AccuWeather Weather Forecast page

Having the weather pushed to a device periodically is useful. The subscriber can tell at a glance what the weather is without ever opening the application.

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