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Mobile Computing has witnessed significant growth in the past two decades, since its initial conceptualization. While the focus of attention has often been the mobile laptop user with roaming WIFI connections (Satyanarayanan, 1996; Bellavista et al., 2001; Pittoura & Samaras, 2001), lately there has been significant focus on developing applications for constrained mobile devices such as smart-phones and Personal Digital Assistants (PDAs) (Sohn et al., 2006; Tomek & Shakshuki, 2009; Sugumaran et al., 2009; Rawassizadeh, 2009).
Application development has always been a challenging task that becomes even more difficult for applications targeting mobile devices where porting issues often prevail. The inability to write once, run everywhere can be attributed to two main reasons:
- 1.
Hardware diversity, i.e., differences in hardware characteristics among mobile devices, like screen size, color depth, memory size, support for peripheral devices like cameras, Bluetooth connectivity, etc.
- 2.
Software diversity, which refers to
- a.
Differences in the underlying operating system (Symbian, PalmOS, etc.)
- b.
Differences in the supported standards, i.e., supported versions of the Connected (Limited) Device Configuration (“Connected Limited Device Configuration (CLDC)”, 2009) and Mobile Information Device Profile (“Mobile Information Device Profile (MIDP),” 2009; Ortiz & Giguere, 2001) of the Java 2 Mobile Edition (“Java ME – The Most Ubiquitous Platform for Mobile Devices”, 2009)
- c.
Differences in the implementation, i.e., vendor specific implementations of MIDP or CLDC APIs, or even vendor/device/series specific libraries and APIs extending or complementing those specified in the standard CLDC and MIDP, for example codecs, graphics support APIs, etc.
It turns out that this diversity is rather difficult to mask off from application developers. Contrary to the desktop and server world, where Java Virtual Machine are almost universally based on SUN’s Java SDK (j2sdk) regardless of Operating System and computer architecture of the machine running the JVM, the Java Kilobyte Virtual Machines (KVM) installed in the mobile phones of today are the manufacturer’s implementation of the KVM specification. This practically means that each mobile device runs a different implementation of the same specification than any other mobile device of another manufacturer. Implementation bugs, combined with the fact that the specification does not always specify completely what a functionality or Application Programming Interface (API) is supposed to do, have lead to an application development and maintenance nightmare for third-part developers of mobile applications. It is an unfortunate fact therefore, that the promise of Java (Gosling, Joy, Steele, & Bracha, 2000) as a “write once, run everywhere” language proved to be overly optimistic in the mobile phone market-place. This is by no means a criticism on the language itself, as Java is probably the best-suited language for writing applications for mobile phones and mobile information devices in general, but rather a realization that the extreme variation in those devices’ characteristics necessitated different versions of the language specifically tailored to these devices. Undoubtedly, the area with the most variations in the offered APIs is the Graphical User Interface, but as different devices support different features and offer the corresponding APIs for developers to take advantage of, there is a wide range of capabilities of different devices and, correspondingly, of the APIs supporting them.