Database Support for M-Commerce

INTRODUCTION M-commerce applications have evolved out of e-commerce applications, riding on the rapid advancement in mobile communication technologies in the past decade. The diffusion of applications on the Internet into the mobile computing environment has taken an accelerating pace ever since. Virtually all e-commerce and m-commerce applications rely on the provision of information retrieval and processing capability. In this regard, database systems serve as the information source and repository for these applications, backed by efficient indexing mechanism. Bean (2003) gave a good report on supporting Web-based e-commerce with XML, which could be easily extended to m-commerce. An m-commerce framework, based on JINI/XML and a workflow engine, was also defined by Shih and Shim (2002). Customers can receive m-commerce services through the use of mobile devices, such as pocket PCs, PDAs, or even smart phones. These mobile devices together with their users are often mod-eled as mobile clients. Central to supporting m-commerce applications are three types of entities: mobile device, mobile communication, and database. In particular, we are more interested in providing efficient access mechanisms to mobile-client-enabled database servers, which are often called mobile databases. Mobile databases contain the core information to support the underlying m-commerce applications, while the use of mobile devices serves for the hardware platform, with mobile communication providing the necessary connection between mobile databases and mobile devices for interfacing with real users or customers. The two major types of data access requirements for a mobile database are data dissemination and dedicated data access. In a mobile environment, data dissemination is preferred, since it can serve a large client population in utilizing the high-bandwidth downlink channel to broadcast information of common interest, such as stock quotations , traffic conditions, special events, or the number of available seats at a performance. On the other hand, dedicated data access is conveyed through uplink channels with limited bandwidth. To disseminate database items effectively, the selected set of hot database items can be scheduled as a broadcast disk (Acharya, Alonso, Franklin & Zdonik, 1995) or the " air storage " (Leong & Si, 1997). The sequence of items to be broadcast is referred to as a broadcast program (Acharya et al., 1995). Proper indexes can be built to facilitate access to database items in the broadcast (Imielinski & Badrinath, 1994). Redundancy can be included to combat the unreliability of wireless communication (Tan & Ooi, 1998). For dedicated data access, queries and updates …