High-Level Goals

High-Level Goals

The general goal of the J2ME standardization efforts discussed in this book is to define a highly portable, secure, small-footprint application development environment for resource-constrained, connected devices. We emphasize the term application development environment. The CLDC and MIDP standards are not intended to replace existing system software stacks or to serve as a complete operating system for small devices. Rather, the goal of these efforts is to define an environment that can be added flexibly on top of an existing system software stack to support third-party application development and secure, dynamic downloading of applications.

The CLDC and MIDP standardization efforts have slightly different but complementary goals. Connected, Limited Device Configuration is intended to serve as a generic, "lowest common denominator" platform that targets all kinds of small, connected devices—independent of any specific device category. Mobile Information Device Profile builds on top of CLDC and focuses on a specific category of devices: wireless, mobile, two-way communication devices such as cellular telephones and two-way pagers.

1 Dynamic Delivery of Java Applications and Content

One of the greatest benefits of Java technology in the small device space is the dynamic, secure delivery of interactive services and applications over different kinds of networks. Unlike in the past, when small devices such as cell phones and pagers came from the manufacturer with a hard-coded feature set, device manufacturers are increasingly looking for solutions that allow them to build extensible, customizable devices that support rich, dynamic, interactive content from third-party content providers and developers. With the recent introduction of Internet-enabled cell phones, communicators, and pagers, this transition is already under way. Several wireless device manufacturers are already offering cell phones that allow users to download new applications such as interactive games, screen savers, banking and ticketing applications, wireless collaboration tools, and so on (Figure).

Note that such customizability is not necessarily limited to communication devices such as cell phones or two-way pagers. For instance, it is quite possible to envision automobile engines that obtain new service programs and updates as they become available, washing machines that download new washing programs dynamically, electronic toys that automatically download updated game programs, and so on. The range of possible applications is virtually endless.

One of the main goals of both the Connected, Limited Device Configuration and Mobile Information Device Profile is to take this transition several steps further by allowing the use of the Java programming language as the standard platform for the secure delivery of dynamic content for these extensible next-generation devices.

2 Third-Party Application Development

The focus on dynamically delivered applications means that CLDC and MIDP are intended not only for hardware manufacturers and their system programmers but also for third-party application developers. In fact, we assume that once Java Powered™ small devices become commonplace, the vast majority of application developers for these devices will be third-party developers rather than device manufacturers.

This focus on third-party application development has some important implications for the features and libraries included in the CLDC and MIDP standards. First, the CLDC and MIDP specifications include only high-level libraries that provide sufficient programming power for the third-party application developer. For instance, the networking APIs included in MIDP provide the programmer with meaningful high-level abstractions, such as the ability to transfer entire files or web pages at once, rather than require the programmer to know about the details of specific network transmission protocols. Second, we emphasize the importance of generality, portability, and interoperability. The CLDC and MIDP specifications are intended to support a wide range of devices and do not focus on any specific single type or brand of devices.

3 Independence of Network Technology Standards

The wireless communications industry has never suffered from the lack of technology standards. There is a plethora of wireless technologies in use all over the world, with varying levels of sophistication, compatibility, and interoperability. The second-generation (2G) digital wireless network technologies include standards such as GSM, TDMA, CDMA, and PDC. Third-generation (3G) wireless network technology standards include WCDMA, CDMA2000, and TD-SCDMA. In addition, there are several second-and-a-half-generation (2.5G) standards such as GPRS, CDPD, and EDGE.

One of the key goals for J2ME standardization efforts is to define solutions that can work effectively with all these network technologies and standards. Any APIs or features that would focus only on one specific type of network technology are generally avoided. An additional goal in the CLDC and MIDP standardization work was to ensure that the solutions can be used both in today's relatively low-speed wireless networks and in tomorrow's high-speed broadband wireless networks.

To reach the goals just mentioned, the CLDC standard defines a special Generic Connection framework for supporting networking in a coherent, extensible fashion. This is discussed in detail in Section 5.3.2, "The Generic Connection Framework." The MIDP standard utilizes the Generic Connection framework and defines a number of concrete network protocols that are guaranteed to be available in all devices supporting MIDP.

3.1.4 Compatibility with Other Wireless Application Standards

A key goal for the standards defined in this book is to provide interoperability with existing and forthcoming wireless application development standards and technology stacks such as Open Mobile Architecture^[1] (OMA) and i-Mode. This means that the application development environments defined by CLDC and MIDP can complement existing technologies rather than compete with them. For instance, today's wireless devices already commonly provide a simple microbrowser for finding services on the Internet. This microbrowser can be extended to locate and launch Java applications as well. A microbrowser augmented with Java application execution capabilities will provide better user interaction and graphics capabilities, support offline use of applications, and make the development of compelling applications generally much easier.

^[1] Defined by Open Mobile Alliance (http://www.openmobilealliance.org/).