PalmDAML Implementation Details

Architecture

1. daml2pdb.java runs under Windows or Unix, reads DAML content using RDF API, and generates a .pdb file suitable for loading into the Palm.
2. PalmDAML.prc is an application that runs on the Palm itself

A single Java program providing similar desired functionality on Windows and Unix platforms is DAML Viewer.

Development Resources and Tools

• Interactive Development Environment (IDE), similar to Microsoft Visual C++
• Constructor for Palm OS, which allows the creation of GUI forms and other resources
• Palm Emulator
• documentation. Suggested reading order:
  • PalmOS Tutorial
  • PalmOS Programmer's Companion
  • PalmOS Reference

As the use of CodeWarrior suggests, PalmOS is quite like the Macintosh OS.

I initially created an empty Starter application in Code Warrior, copied the files, and started editing.

My normal edit/compile/debug cycle is

• emacs
  • edit and save PalmDAML.cpp or other files
• CodeWarrier IDE
  • use the "Synchronize Modification Dates" and "Build" buttons within the PalmDAML.mcp window to build PalmDAML.prc
• Palm Emulator
  • Use "Install Application/Database" to load the updated PalmDAML.prc file.
  • Use "Install Application/Database" to load the .pdb file (if it hasn't been loaded already).
  • Click Home.
  • Click PalmDAML to launch the application.

Compared to an actual Palm device, Palm Emulator provides better debugging support and a better display, and doesn't run down batteries or risk stored data. I used Palm Emulator 3.0a7, downloaded separately, with palmos35-en-ezdbg.rom (you have to join the Solution Provider Program to download ROM images).

Source code is stored in CVS, in the palm module under CVSROOT :pserver:@www.daml.org:/home/mdean/daml_cvs_root. This (unfortunately) includes some binary files such as PalmDAML/Rsc/Resource.frk/PalmDAML.rsrc.

Issues

• the small screen (160 x 160 monochrome pixels)
• the small dynamic heap (32K - 128K, see here for this and other details -- most of the 1M - 8M memory is used for database storage).

Less constraining issues are

• the limited CPU (16-20 MHz Motorola 68000 series Dragonball)
• the limited bandwidth of the serial and IR interfaces

Current Design

daml2pdb.java now creates the graph structure and stores a database record for each node (Resource, Statement, or Literal). The exact database strucuture is described in comments at the head of daml2pdb.java.

PalmDAML starts with a NodesView (note plural) listing the URIs of all Resource nodes found in its single database. When the user selects one of these URIs, he gets a NodeView (note singular) showing all of the statements involving that node.

We have officially registered the Creator ID "DAML" for use with PalmDAML.

Future Plans

1. investigate the use of a Table rather than a List for displaying statements on the Node screen
2. modifications to the Node screen
   • ensure that the full URIs and content can be viewed on the Node screen. This screen might be split into a top pane listing statements and a bottom pane showing the full information for 1 selected statement.
   • ensure that the user can navigate to any of the predicate, object, or reifications for a given statement.
3. implement the Back button (and maybe a Forward button)
4. modify the GUI to be compatible with the User Interface Guidelines in Companion.pdf
5. investigate modifying the NodesView List to dynamically fetch choices directly from the database entries based on the current scroll bar settings rather than requiring that a static list of choices be computed initially
6. link the scroll bars to the Palm scroll keys
7. supply About ... information for the application, e.g. "PalmDAML 1.1 (or 2000-11-21) developed by Mike Dean and Jack Margerison of BBN Technologies"
8. support use of the standard Palm Find interface to search DAML records
9. consider replacing daml2pdb with a Conduit that allows incremental transfer of new DAML statements.
10. investigate wireless and/or IR transfer of statements (Windows NT doesn't generally support IR devices, but Windows 2000 does)
11. ...