View Propagation and Inconsistency Detection for Cooperative Mobile Agents

Abstract

Mobile agents are autonomous programs that migrate from one machine to another within a network on behalf of a client, thus, they are ideal for mobile computing environments since tasks can be delegated to mobile agents when a mobile client is disconnected. This paper extends the traditional functionality of a mobile service agent with capabilities that facilitate asynchronous cooperation among mobile database clients. In the context of mobile client-server database applications, data cached to support disconnected operations can take the form of a materialized view. We design mobile agents to reduce computation and wireless communication costs, and use view versioning to cope with disconnected operations by allowing application sessions to access current data without invalidating work previously done. A data validation or results propagation process detects inconsistencies with newer versions of data upon reconnection. Essentially, these mobile agents will compute the period of time or consistency window, measured in versions, for which the results of a mobile client's application are consistent. We supply rules that govern the creation and sharing of results and show how inconsistencies can be detected to offer a higher availability of data while organizing and gracefully degrading the amount of consistency achieved between the mobile clients and the data sources.