January 28, 2005
Developer case study:
Wayfinder and how to install a 500kB application in just 30kB

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Wayfinder is an application development company located in Lund, in the south of Sweden. Wayfinder EuroGuide™ is a mobile city guide, direct in your mobile phone. You can get detailed maps and information for Western Europe, including over one million Points of Interest (POI) such as hotels, restaurants, museums, bars and much more. By entering a starting point and destination, you'll directly receive the route on your mobile phone. Via GPRS, the mobile phone communicates with the Internet-based Wayfinder server and sends the chosen route information to your phone. The Wayfinder EuroGuide™ is downloaded from the Internet onto a user's mobile phone.

Wayfinder EuroNavigator™ is an application that helps a user find places and get route descriptions from all over Western Europe delivered directly to their mobile phone. Together with a small GPS receiver, the Wayfinder EuroNavigator™ software turns a mobile phone into an off-board navigation system. Users receive the information they want within just a few seconds via GPRS from the Wayfinder server. The Internet-based Wayfinder server stores maps s well as millions of Points of Interest for the wole of Western Europe. The data transmissions are kept to a minimum in order to deliver a cost-efficient navigation service. After simply entering a destination in the phone, the shortest or fastest route (depending on user choice) will be calculated and sent as voice directions, navigational icons and area maps or moving maps. The route calculation uses digital maps from Tele Atlas and high-quality Points Of Interest from Wcities. The detailed voice directions can be sent in 12 different languages.

Both the Wayfinder Navigator and EuroGuide are compatible with the Sony Ericsson P800, P900 and P910 series of smartphones.

Sony Ericsson Developer World recently talked to Wayfinder about their experiences with developing these smartphone applications.

Why did you choose to develop for a certain phone/platform? Why was this particular device and platform useful to you?

Stefan Bengtsson, Director of Research and Development at Wayfinder Systems AB, said, "The Wayfinder Mobile Navigator targets the Symbian platform. We decided to create a Symbian application because we believe that it is a platform that will be very strong in the smartphone segment and it's still one of a very few platforms where it's technically possible to implement a full navigation service, including GPS interaction, dynamic maps, etc."

He continued, "We've also started to implement a J2ME version. The reason behind this is that Java is a very common platform and it'll give us access to the mass-market. We also believe that the functionality offered in the Java platform will increase and that it will soon be possible for us to deliver the navigation service to a lot of different phone models."

Wayfinder uses an iterative process when developing software. It starts with a proper analysis and design, and then iterates over low-level design, implementation and testing.

Any particular challenges or problems?

Stefan responded, "The first challenge was to learn the Symbian operating system. It's very similar to other operating systems, but still different. At this point in time, after more than 2 years of development for the Symbian platform, we feel that we know it very well. One of today's biggest challenges is to make sure that our applications work on all Symbian devices - different flavors of UIQ, but also the other Symbian platforms."

Wayfinder is also aware of the download size restrictions in many operator gateways. Because of this, they've worked out a two-stage process for download and installation for their EuroNavigator application, creating the GetWayfinder application.

GetWayfinder helps overcome file download problems

Before a user even can start to use Wayfinder EuroNavigator, the application needs to be downloaded and installed on the device. There are a couple of possibilities for how to do this. The user can either download the correct files to a PC and from there to their smartphone or get the file using the built-in WAP browser. The first alternative requires a PC and docking device, but the second offers the possibility of downloading and installing the application "on the fly".

However, Wayfinder found that the WAP gateways of some operators restricted the downloaded application size, in some cases to a maximum of 30kb. Since Wayfinder is a large and complex product, hundreds of kb in size, Over-the-Air (OTA) downloading wasn't an alternative that could be used.

To work around this problem, Wayfinder decided to use a two-stage process for download and installation, creating the GetWayfinder application.

The idea was to create a small application of less than 30kb, that could then use a true Internet access point to download the real application via HTTP over TCP/IP, and then launch the built-in installer to install the application files.

The download process starts when a user receives an SMS with a link to the GetWayfinder application. In a normal SMS inbox program, a user can launch the built-in WAP browser with the link in the screen dump below.

The link includes different information such as device architecture, requested language, user identification, etc. The GetWayfinder program is downloaded and installed and the user now runs GetWayfinder.

When GetWayfinder is run for the first time, it contacts a specific web server to download information on which files to download. This is referred to as the "package list" and contains information on the latest version numbers and file sizes.

GetWayfinder can then compare the version number with an already installed Wayfinder EuroNavigator and determine if a download is required.

If a download is required, GetWayfinder starts to download the data for a specific .sis file using a CFileDownloader class that then saves the data to a specific file.

void CFileDownloader::SaveData(const TDesC aURL, TFileName aFileName);

The function opens a TCP/IP connection to the server specified in the URL and sends data for an HTTP GET request of the rest of the URL. The data is then downloaded in chunks and saved to the file aFileName.

When the download is finished, GetWayfinder starts the built-in application installer using the recently downloaded .sis file as argument.

void CFileDownloader::InstallFile(TFileName aFileName)
{
// Start SIS installer...
 RApaLsSession session;
User::LeaveIfError(session.Connect());
 CleanupStack::PushL(&session);
TThreadId threadId;
session.StartDocument(aFileName , threadId);
CleanupStack::Pop();
  
TInt res = iInstallerThread.Open(threadId);
if( res == KerrNone ){
if (!iProcessWait) {
iProcessWait = ProcessWaiter::NewL(this,
&iInstallerThread);
     }
iProcessWait ->Start();
     iState = EUpdateStateWaitingForInstaller;
 } else {
  // Do something graceful here...
}
}

GetWayfinder then waits for the installation to finish before continuing with the next file in the package list.

 nextFile = aFileList.shift();
while (nextFile.Valid()) {
     // More files to download
     CheckVersionAndDownload(nextFile);

nextFile.Action(); // Will perform correct
       // action (delete, install)
      nextFile = aFileList.shift();
 }

A normal case includes two files, one for the application and one for resources such as sounds and images. The split is done because some older devices can't install large (more than 1MB) .sis files.

GetWayfinder can do a number of actions with downloaded files besides just installing them. There is a command field that can indicate that the downloaded file should be copied to a specific location, or removed from the device.

The future of Wayfinder

The download size limit that originally gave reason for the creation of GetWayfinder has since been increased, and some operators have now completely removed it. This reduces the value of GetWayfinder as a stand-alone program, but the possibility of downloading a "package" will continue to be an important feature and Wayfinder considers the inclusion of this feature in the Wayfinder EuroNavigator to be very important.

Stefan Bengtsson concluded the interview with commenting on the assistance that Sony Ericsson Developer World has provided. "We've got access to very good technical support from Sony Ericsson Developer World, and we feel that its services are working very well for us."

Wayfinder demo in Sony Ericsson's booth at the Symbian Expo 2004.

• www.wayfinder.com
• Get Wayfinder Mobile Navigator from Sony Ericsson Application Shop>>
• Sony Ericsson technical developer support>> 
• Sony Ericsson and partners at Symbian Expo 2004>>