Wednesday, December 1, 1999

Developing a Palm VII PQA that reads data from a Domino database

BUILDING WIRELESS APPLICATIONS

By Bruce Elgort

When I first purchased my Palm VII back in July, I thought the applications that ran on the organizer would require me to learn yet another development framework. I had heard that developing Palm OS applications wasn't a trivial task. Much to my surprise, however, I learned that developing a Palm Query Application (PQA) to read data from a Lotus Domino database was a relatively simple process.

Don't get me wrong -- as the complexity of an application increases, so does the development of the PQA and the back-end Web clipping and processing of files and scripts. But it's not as bad as it sounds.

There are two parts to a Palm Query Application that you need to develop:

  • The Palm Query Application itself, which will reside on the Palm VII organizer.
  • A Common Gateway Interface (CGI) script, or, in the case of Lotus Domino, a LotusScript or Java Agent that generates Web clippings using data from a Domino database. The Web clippings are sent back to the Palm VII as HTML.

"You only clip the information you need, instead of all the articles and photos on the page."

What is a Web clipping?

The term "Web clipping" is based on the analogy of clipping an article out of a newspaper -- you only cut out or "clip" the information you need and not all the articles and photos on the page. Since the display of the Palm VII is limited in size, trying to display Web pages designed for an 800 by 600 dpi screen is impossible. So when you, as a developer, are writing a PQA or an agent to generate a Web clipping, keep the user in mind and give them only what they asked for. Don't give them any flaming logos!

The Palm Query Application

The Palm Query Application is made up of one or more text files and graphics that are authored in a subset of HTML version 3.2. You can use WordPad or any text editor or HTML authoring tool to develop these files. The files are compiled into a PQA using the Query Application Builder tool available from the 3Com Palm.Net Web site. You can then use the HotSync utility supplied with the Palm VII and install the PQA on your organizer.

When developing PQAs, it's important to remember that you aren't developing Web pages for a fast Pentium PC with a 19" monitor and a 56kb modem. You're developing them for a monochrome device with a screen resolution of 160 by 160 pixels that communicates at an effective transmission speed of between 8 kilobytes per second to 19.2KB/second. You need to use the screen real estate effectively. PQAs are based on a simple query and response metaphor in which the user enters and/or selects choices from the PQA and a discrete set of information is returned as a Web clipping to the user.