1. Introduction

The environment of mobile computing is in many respects very different from the environment of the traditional distributed systems of today. Bandwidth, latency, delay, error rate, interference, interoperability, computing power, quality of display, and other non-functional parameters may change dramatically when a nomadic end-user moves from one location to another, or from one computing environment to another - for example from a wired LAN via a wireless LAN [4] (WLAN) to a GPRS [20] or UMTS [33] network. The variety of mobile workstations, handheld devices, and smart phones, which nomadic users use to access Internet services, increases at a growing rate. The CPU power, the quality of display, the amount of memory, software (e.g. operating system, applications), hardware configuration (e.g. printers, CDs), among other things ranges from a very low performance equipment (e.g. hand held organizer, PDA) up to very high performance laptop PCs. All these cause new demands for adaptability of data services. For example, palmtop PCs cannot properly display high quality images designed to be looked at on high resolution displays, and as nomadic users will be charged based on the amount of data transmitted over the GPRS network, they will have to pay for bits that are totally useless for them.

Software agent technology has gained a lot of interest in the recent years. It is widely regarded as a promising tool that may solve many current problems met in mobile distributed...