Frequently Asked Questions (FAQ)

  1. Q:What is being demonstrated by this package?

    A: This demo is intended to show off the powerful potential capability of MoDAL-TSpaces approach for Pervasive Computing. It demonstrates a partial but operational behavior of MoDAL language and translation system (Engine) which together make a powerful tool for TSpaces mobile clients. TSpaces can be found at . For more information on MoDAL and how to run it, please visit the MoDAL Web Page at

  2. Q: What has been included in this package?

    A: The package ( file) is the demo package for MoDAL version 1.0. The package includes a set of programs and example files to demonstrate the basic functionality of MoDAL. It consists of the MoDAL Engine Version 1.0, Java Proxy, and sample MoDAL programs. As MoDAL requires TCP/IP, you have the following options:

    1. Emulator: Palm OS Emulator (POSE) 2.1d26 or above. You can download the latest POSE from .
    2. Real device using wireless modem: Use a real Palm or Workpad with a wireless modem, such as the Novatel Minstrel.
    3. Real device using cradle: Use a real Palm or Workpad in the cradle. We use NT or Linux (it seems like Windows 9x should work, but we havenít been successful). When using NT, you must enable RAS (Remote Access Services) - see connection with NT page for details.

    More specifically, this package consists of the following files:

  3. Q: What else is required to run the demo?

    A: You need the following programs in addition to the files included in this package:

    TSpaces is available at IBM's Alphaworks site at POSE and Palm ROM are available at

  4. Q: What makes MoDAL different from existing standards (such as HTML)?

    A: MoDAL has been specifically designed to negotiate for and use resources provided by both TSpaces and the handheld devices. This will make it possible for a MoDAL-enabled palm device to maintain MoDAL applications and user preferences locally, yet still making use of powerful TSpaces services when connected to a network.

    The MoDAL interpreter is also designed to be a two-way client. That is it can be interrupted (or woken up) by the server (though this was not implemented in version 1.0). Currently, web browsers can only ask for information, they cannot accept unsolicited data from servers.

  5. Q: After loading my MoDAL application eight times, the MoDAL engine crashes.

    A: We are aware of a memory leak affecting the number of times a MoDAL program can be run. Because of the current (im)maturity of the development environments for palm devices, memory leaks can be especially difficult to track down. This problem is expected to be resolved in future releases.

  6. Q: How do I recover from such a crash?

    A: If this crash should occur, a soft-reset should restore the system without requiring any additional cleanup.

  7. Q: How do I make my MoDAL application use several forms?

    A: You may define several forms in a MoDAL application. You must have a form named "main" - the MoDAL interpreter will always start this form first.

  8. Q: Why do I need the proxy (ProxyPC)?

    A: The proxy serves the purpose of converting the Java object version of tuples into non-java versions of tuples. This conversion was necessary because at the time the MoDAL development commenced, there were no JVMís available for palm-sized devices. It is also worth noting that even though limited versions of Java are available on palm-sized devices, we cannot be certain that all potential MoDAL hosts will be compatible with Java.

  9. Q: What kinds of data can I transmit and receive from TSpaces using MoDAL?

    A: MoDAL currently supports tuples of any size containing String fields. We are planning to provide support for additional data-types including sub-tuples - look for this in future releases.

  10. Q: When I start the MoDAL application, I see a screen containing fields for user-id, password, and host. What do I do here?

    A: Just press the "ok" button and you should be registered with the proxy (assuming the proxy is running on your local machine). If you are running the proxy on a different machine, you may change the value in the "host" field. The other (default) values should always work.

  11. Q: Once Iíve logged into the Proxy using MoDAL, how do I run a MoDAL application?

    A: Select "remote" from the pull-down menu on the top right corner of the MoDAL manager screen. A list of the available MoDAL applications should appear after a moment. If not, check to be certain the proxy is running and the MoDAL applications directory (.../MoDAL) is not empty.

  12. Q: What devices will MoDAL run on?

    A: This initial implementation of the MoDAL engine runs on IBM WorkPads and other Palm-III and Palm-V based devices. As MoDAL development continues, we hope to extend support to Windows CE devices, pagers, and mobile phones - potentially a comprehensive set of mobile devices.

  13. Q: Iíve created a new MoDAL application. How do I run it?

    A: New MoDAL applications may be run by putting the .xml file in the same directory as the sample MoDAL applications. The next time you list the available MoDAL applications from the MoDAL manager, your new file will appear.