PC-to-Mobile Communication API

Comparison of the Ewe VM with a PersonalJava VM.. 1

Portable and Synchronizable Database Implementation. 5

Comparison of the Ewe VM with a PersonalJava VM

The Ewe VM is targeted at devices at the PDA level and higher. That is to say, a 32-bit OS with at least a 160x160 touch screen, and at least 2 MB of available program memory. The standard Java specification that also targets such devices is Sun's PersonalJava. (The Java Micro Edition spec. is targeted at devices with much smaller memory footprints, smaller displays and very limited I/O capabilities - Ewe does not attempt to fit into such devices).

The most well known PersonalJava VM available is the Jeode EVM – and it appears to be the only PersonalJava VM that comes standard with any PDA platform; specifically the Sharp Zaurus line of PDAs. Although versions of this VM are available for different platforms (e.g. PocketPC) none of them are available for free.

The table below compares some of the essential features of the Ewe VM and the Jeode EVM. The comparison was made on the same Sharp Zaurus 5500 device.

	Ewe VM	Jeode PersonalJava EVM
Static Storage Space	2.0 MB	2.7 MB
Runtime Memory (Min.) ¹	550K	1600K
Start-up Time ¹	< 1 second	2.5-3 seconds
GUI Feature Set	Advanced	Simple AWT
Zip File Utilities	Yes	Yes
Image Display and Writing	Yes	Display only
Socket API	Yes	Yes
Serial Port API	Yes	Yes
Infra-Red API	Yes	No
Desktop to Mobile Communication	Yes	No
Portable Database Implementation	Yes	No
Automatic Synchronization of Databases	Yes	No
Registry Access	Yes	No
Native Method API	Yes	Yes

1. Runtime memory and Start-up Time were measured by each VM running a simple application that displays a "Hello World" dialog box.

Availability

Ewe is available, free of charge, for the most number of mobile and platforms to date. This includes:

All PalmPC platforms.
All PocketPC platforms.
All HandHeld Pro platforms.
The Casio BE-300 PDA.
The Sharp Zaurus PDA.
Windows Desktop.
Linux Desktop.

And coming soon for:

PalmOS 5 PDAs
The Simputer Linux PDA.

Additionally, Ewe applications will run on any system with a Java 1.1 virtual machine or better.

Performance and Storage Requirements

The Ewe VM and its class library were designed from the ground up to be targeted at Mobile Platforms. The PersonalJava specification is in reality, simply a stripped down version of the Java 1.1 specification – originally designed for desktops. Unfortunately the design principles that were applied for the development of Java 1.1 simply do not translate well to the mobile device.

The Jeode PersonalJava VM uses standard Jar files to store its class files. While this may reduce the storage space required by the VM it does not help at all reducing the dynamic space required when running, since the classes must be uncompressed, and then translated into internal data structures. Further, uncompressing, these class files takes up considerable time at program start up. Users may be prepared to wait 3 seconds for an application to start on a desktop, but this is generally not acceptable on a mobile platform – especially when the other applications start virtually instantaneously.

The Ewe VM uses a proprietary storage format for its system classes that allows the class library to be memory mapped and used directly, instead of needing to be decoded and restructured in memory. The result is a dramatic difference in the runtime memory usage and start up time.

On average, the Ewe VM starts 3 times faster and uses 3 times less memory than the PersonalJava VM.

This is no minor detail. The Casio BE-300 device is a medium powered device that has about half the memory of the Zaurus and runs at about half the clock speed. Yet the Ewe VM on the Casio BE-300 starts faster and uses far less memory than the EVM on the Zaurus. In fact, you can run several Ewe applications on the BE-300 or Zaurus simultaneously (up to six running at the same time have been tested) with no memory or performance problems at all.

Advanced GUI Features

The Ewe GUI library provides advanced GUI features not available in the Java AWT environment. These features are comparable to the Swing GUI features available for Java 1.2, but in a size that can actually fit on a Mobile device. Here are some features that are available in the Ewe library, but not on the PersonalJava platform:

Adjustable Split-Panels – User adjustable split-panels.

Tabbed Panels – With tabs placed on top or below, depending on the running platform or programmer choice.

Table Controls – Fully customisable and user resizable. Table controls can actually contain other controls within their cells.

Tree Controls – Fully customisable. Tree controls can also contain other controls within their nodes.

Date Chooser Control – Lets users select dates from an easy calendar like display.

Mosaic Panels – These allow any number of animated images to be displayed and allow the user to interact with them. This includes dragging them around, dropping them on other images, etc.

Drag and Drop – Drag and drop data within and between controls.

Tool Tips – Full tool tips with images and text for all controls.

Ewe also features a FileChooser dialog box that is far more advanced than the standard Java file chooser box, yet adjusts itself and works equally well on a desktop or mobile platform.

Here is the FileChooser in two different forms on the Zaurus:

The second screen shot shows Tree controls, Table controls (the file list), and Tabbed controls. Note that the Tabbed control displays full icon and text for the selected tab, but only the icon for the unselected tabs. This is a very useful technique for saving space on mobile devices. Note also that it is possible to embed other controls on either side of the tabs in a Tabbed control. Again, this is very useful for saving space on mobile devices.

Compare this with the Jeode PersonalJava EVM FileDialog box:

As you can see it only covers half the screen and provides virtually none of the richness and usability of the Ewe FileChooser, not to mention taking about three times longer to be initially displayed.

Ewe provides a number of advanced GUI data transfer as part of its standard library. These features allow you to transfer data between a Java object and an on screen user interface with virtually no programming.

Look at the example code below. It shows how a Java object can be automatically transferred and edited on-screen by the user with no extra programming. The Editor object has the capability to extract the public fields within the class and determine the best user interface and prompt to use for each field.

//##################################################################

public class Contact{

//##################################################################

public String lastName = "Simpson";

public String firstNames = "Homer Jay";

public String phoneNumber = "868-321-3325";

public ewe.sys.Date birthday = new ewe.sys.Date(1,5,1950);

public boolean business = true;

//===================================================================

public String toString(){return firstNames+" "+lastName+"\n"+birthday;}

//===================================================================

public static void main(String args[])

//===================================================================

{

ewe.sys.Vm.startEwe(args);

Contact c = new Contact();

ewe.ui.Editor ed = new ewe.ui.Editor();

ed.setFields(c);

ed.title = "Contact Info";

ewe.ui.Gui.setOKCancel(ed);

if (ed.execute() == ed.IDOK)

new ewe.ui.MessageBox("Entered","You entered: \n"+c.toString(),ewe.ui.MessageBox.MBOK)

.execute();

ewe.sys.Vm.exit(0);

}

//##################################################################

}

//##################################################################

When executed, this code produces the following form:

Even more advanced data transfer features are available in Ewe that greatly reduce the amount of coding required to go from object data to user interface.

Communication Capabilities

Ewe provides the standard TCP/IP capabilities of Java, including Socket and ServerSocket classes. Additionally Ewe provides, on mobile devices, the ability to set up a ServerSocket to listen to incoming Socket connections on an Infra-Red port. This is as easy as using the host name "infra-red" when creating a ServerSocket or Socket. This allows Ewe applications to communicate across the Infra-Red link even between different mobile devices. Infra-red communication between the Zaurus and PocketPC have been fully successful using this API.

Ewe also provides a SerialPort class for communicating on the serial port of devices or desktop PCs.

Mobile to Desktop Communication

Ewe provides, on all platforms, an API and implementation for Ewe applications on the desktop to run and communicate with Ewe applications on the mobile device. A EweSync service provides this communication across ActiveSync (for WinCE devices) and across the Zaurus USB link. This service not only provides a uniform communication service across the different platforms, but also allows for the automatic execution of Ewe applications once this link is made. This allows for fully automatic synchronization of Ewe applications once a device is connected to the PC. No other mobile Java platform provides this kind of cross-platform API.

Portable and Synchronizable Database Implementation

Ewe provides a full implementation of a searchable, sortable platform-independent database. Fields within the database can be set directly from the fields of a Java class and that same class can be used as a data interface between your application and records within the database.

The implementation even allows the database to be set up to facilitate synchronization with a database on the desktop, through the Mobile to Desktop link.