Escrow techniques for mobile sales and inventory applications

Abstract

We address the design of architectures and protocols for providing mobile users with integrated Personal Information Services and Applications (PISA), such as personalized news and financial information, and mobile database access. We present a system architecture for delivery of PISA based on replicated distributed servers connected to users via a personal communications services (PCS) network. The PISA architecture partitions the geographical coverage area into service areas, analogous to PCS registration areas, each of which is served by a single local server. When a user moves from one service area to another, the service is provided by the new local server. This is accomplished by a service handoff, analogous to a PCS call handoff, which entails some context information transfer from the old to the new server. We focus on the mobile sales and inventory application as an example of a PISA with a well‐defined market segment. We design a database management protocol for supporting both mobile and stationary salespersons. Our design uses the site‐transaction escrow method, thus allowing faster responses to mobile clients, minimizing the amount of context information which must be transferred during a service handoff, and allowing mobile clients to operate in disconnected mode by escrowing items on their local disks. We develop a formal model for reasoning about site‐transaction escrow, and develop a scheme for performing dynamic resource reconfiguration which avoids the need for time‐consuming and costly database synchronization operations (i.e., a two‐phase commit) when the mobile sales transaction completes. A further refinement to the scheme avoids an n‐way two‐phase commit during resource reconfiguration operations, replacing it with several simpler two‐phase commits.