Mobile map - Technology for Application

The application can then be classified as distributed or local. Distributed applications typically involve both a client component and a server component of the application,whereas a local application resides on a single device.

Application development is always constrained by the target platform's capabilities.This is especially true for the "ultralight" J2ME platform,because developers face many difficulties related to the platform's physical limitations.These difficulties include :

  1. The physical screen size (96*128 to 176*208) pixel,this covers a display area (12288 to 36608) pixels.
  2. Limited Input/Output capabilities.
  3. Limited memory.
  4. Limited processing power.
  5. Intermittent network connections.
These characteristics are defined in J2ME configurations(CLDC) which provide specifications for all java–enabled mobile devices.

System Application Mode
There are three mode of mobile map applications based on the connectivity.These categories are:

  1. Offline mode (standalone), the application and data stored locally on the compact flash card.
  2. Server connected mode,only application (not always) has been installed locally,but all data comes from centralaized database stored in the server.
  3. Hybrid mode,some data has been installed locally and frequently business data will be fetched from server.
Each mode has its own advantage and disadvantage.Offline mode can work independently(anytime and anywhere).In this mode, All data must to be installed in advance and therfore it will not provide dynamic information.On the other hand,the connected mode might be expensive to access the application and wireless connections can occasionaly drop off due to low signal strength.

Overview of the Java 2 Micro Edition Platform
J2ME is aimed squarely at consumer devices with limited resources(memory-display size and processing power). Many such devices have no option to download and install software beyond what was manufacturing process.With the introduction of J2ME, devices no longer need to be "static" in nature.

Like its enterprise(J2EE),desktop(J2SE) and smart card (Java Card) counterparts,the J2ME platform is a set of standard Java APIs defined through the Java Community Process (JCP) program.

The J2ME Architecture
The J2ME architecture defines configurations, profiles and optional packages as elements for building complete Java runtime environments that meet the requirements for a broad range of devices.

Configurations,are composed of a virtual machine (VM) and a minimal set of class libraries.They provide the base functionality for a particular range of devices that share similar characteristics,such as network connectivity and memory footprint.Currently there are two J2ME configurations:the Connected Limited Device Configuration (CLDC) and the Connected Device Configuration (CDC).CLDC is designed for devices with intermittent network connections,slow processors and limited memory-devices such as mobile phones, two way pagers and PDAs.

Profiles,In order to provide a complete runtime environment targeted at specific device categories,configurations must be combined with a set of higher level APIs,or profiles ,that further define the application life cycle,the user interface,and access to device specific properties.

The Mobile Information Device Profile (MIDP) offers the core application functionality required by mobile applications,including the user interface,network connectivity,local data storage, and application management.Combined with CLDC,MIDP provides a complete Java runtime environment that leverages the capabilities of handheld devices and minimizes both memory and power consumption.

Optional Packages,The J2ME platform can be further extended by combining various optional packages with CLDC and their corresponding profiles.Created to address very specific requirements,optional packages offer standard APIs for using both existing and emerging technologies such as Bluetooth, web services,wireless messaging and database connectivity.

In addition to J2ME's configurations,profiles and optional packages Figure (2) shows that applications may draw on vendor-specific interfaces when needed.These are not parts of standars J2ME,but extend or provide functionality that is specific to a given device.We can think of vendor-specific APIs as extensions to configurations and profiles.


Figure (2): The organization of J2ME



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