CAREER: Developing Pragmatic Mobile Data Management Systems

Panos K. Chrysanthis

Contact Information

Panos K. Chrysanthis
Department of Computer Science
University of Pittsburgh
Pittsburgh, PA 15260
Phone: (412) 624-8924
Fax : (412) 624-8854
Email: panos@cs.pitt.edu
URL: http://www.cs.pitt.edu/~panos

WWW Page

http://www.cs.pitt.edu/admt/projects/mobile.html

List of Supported Students

Graduate Student Researchers: Stavros Papastavrou, and Susan Weissman-Lauzac
REUs: Robert Mclaughlin, Gloria A. Santin, and Scott Wood

Project Award Information

• Award Number: IRI-9502091
• Duration: 7/1/1995 - 8/31/2000
• Title: CAREER: Developing Pragmatic Mobile Data Management Systems

Keywords

Mobile Computing, Transaction Processing, Disconnected Operations, Data Replication and Caching, Materialized Views.

Project Summary

The objective of this research is to develop innovative techniques that would make access to shared data by mobile computer users possible, anywhere and at anytime. In order to overcome the inherent limitations of mobile environment, we have developed PRO-MOTION, a flexible and adaptive infrastructure to support disconnected transaction processing in a mobile, client-server operating environment. By means of negotiated agreements, PRO-MOTION supports data caching and dynamic data replication on mobile clients and realizes both traditional as well as application specific data and transaction correctness criteria. We have also developed a prototype of a query processing facility that supports the exploration and query of databases from a mobile computer. A user can be involved in the formulation of queries while the mobile computer is disconnected from the network. Complete queries are formulated on metadata stored on the mobile computer in an incremental manner and without involving access to the actual data in the remote database to materialize intermediate steps. In the same context, we explored the idea of maintaining cache data on a mobile client as versions of materialized views and proposed an extension to SQL that allows a mobile computer to program these versions. Further, we developed optimizations for read-only transactions by combining data and control information in broadcasts to the mobile clients. In the course of our investigation, several commit protocols applicable in distributed database systems in general were also developed.

Goals, Objectives, and Targeted Activities

This year our goals and objectives are:

• Continue the collaboration initiated in IDM99 with S. Mazumdar at NMIT in applying the notion of localization of global constraints in PRO-MOTION to ensure integrity constraints despite disconnections.
• Continue our investigation on the development of a dynamic and customizable view maintenance mechanism for mobile access. Further, empirically evaluate Java-based approaches including mobile Java agents to support view materialization and Web database access.

Indication of Success

The project has already met most of its initially stated goals and went even beyond them. Further, it has already had an influence on research work by others. The initial focus on data management in mobile environments had been on supporting efficient data retrieval and attempting to minimize energy consumption by the mobile computer. This project raised the issue of local updates on shared data on a mobile computer and proposed the first mobile transaction model. The first indication of its success is its impact on most of the subsequently developed mobile transaction models.

PRO-MOTION is one of the three different infrastructures proposed for mobile transaction processing and, in conjunction with our work on customizable views mechanism, is expected to contribute to the better understanding of (1) disconnected and autonomous mobile database operations, (2) data caching and dynamic data replication, and (3) the mechanism needed to support them. The fundamental building blocks of PRO-MOTION are compacts, which are the realization of our proposed notion of agreements and function as the basic unit of caching and control. Compacts encapsulate access methods, state information, consistency constraints (including temporal ones), restrictions, obligations, and privileges along with the shared data. Interestingly, the first impact of compacts went beyond the area of mobile computing as it can been seen in the work of J. Waesch, T. Tesch and W. Klas, researchers at GMD at Darmstadt, in semantics-based transaction management for cooperative applications.

Project Impact

• Eight MS/Ph.D. students have been involved in and partially funded by this project which ends this year. One of them completed his Ph.D. dissertation in May 1997 and is currently an Assistant Professor abroad. One is working on her dissertation. Four more students completed their MS degree and each joined Oracle, the Chemistry Department at the University of Pittsburgh, Carnegie Institute and B-Right Company.
• As with our prior NSF project, this project too involved undergraduate student interns and REUs (Research Experience for Undergraduates). Currently the project involves 1 REU. Out of the four graduated REUs, three continued graduate school with scholarships in our department, at Princeton, and at the University of Virginia.
• We offered a Ph.D. seminar on "Mobile Computing and Data Management'' in which traditional database techniques were reevaluated and emerging approaches were examined. Based on this and previous Ph.D. seminars as well as on our own research work, we co-authored a book on advanced transaction processing published by IEEE Press, for which we received excellent reviews and feedback on its usefulness from both experienced researchers and graduate students alike.
• We organized the first ACM international Workshop on Data Engineering for Mobile and Wireless Access, 1999, and the 1999 and 2000 DEXA Workshop on Mobility in Distributed and Database Systems.
• We established a distributed database laboratory and wireless Ethernet network in our department providing network access in classrooms. These enabled us to participate in Oracle's and IBM-DB2 educational programs and use their servers in our course lectures and projects, significantly enhancing our undergraduate database curriculum.
• This award triggered collaboration with B-Right Tracking Company, a major common and contract carrier based in Ohio, which provided us with both additional funding as well as real mobile database applications.

GPRA Outcome Goals

The goals of this project are in agreement with the long-term vision of universal access, providing data access, anywhere and at anytime, while taking into account the individual user's specific needs. Every attempt is being made to develop theoretical frameworks and then transfer them into pragmatic environments and so their impact is far-reaching in the commercial sector. The project thus far has attracted a diverse body of students, including women, who are particularly under-represented in this research community.

Project References

· P. K. Chrysanthis. Transaction Processing in a Mobile Computing Environment. IEEE Workshop on Advances in Parallel and Distributed Systems, pp. 77-82, Oct. 1993.

· Panos Chrysanthis and Krithi Ramamritham. Synthesis of Extended Transaction Models Using ACTA. ACM Transactions on Database Systems, 19(3):450-491, Sept. 1994.

· G. Walborn and P. K. Chrysanthis. Supporting Semantics-Based Transaction Processing in Mobile Database Applications. The 14th Symposium on Reliable Distributed Systems, pp. 31-40, Sept. 1995.

· Massari, S. Weissman, and P. K. Chrysanthis. Supporting Mobile Database Access through Query by Icons. Distributed and Parallel Databases Journal, Vol 4., No. 3, pp. 249-270, July 1996.

· Y. J. Al-Houmaily, P.K. Chrysanthis and S. Levitan. An Argument in Favor of Presumed Commit Protocol. The 13th IEEE International Conference on Data Engineering, pp. 255-265, April 1997.

· G. D. Walborn and P. K. Chrysanthis. PRO-MOTION: Support for Mobile Database Access. Personal Technologies, Vol. 1, No. 3, pp. 171-181, Sept. 1997.

· P. K. Chrysanthis, G. Samaras and Y. J. Al-Houmaily. Recovery and Performance of Atomic Commit Protocols in Distributed Database Systems. Recovery in Database Management Systems, V. Kumar and M. Hsu, eds., Prentice Hall, 1998

· S. Weissman-Lauzac and P. K. Chrysanthis. Programming Views for Mobile Database Clients. The 9th DEXA Workshop on Mobility in Databases and Distributed Systems, pp. 408-413, Aug. 1998.

· E. Pitoura and P. K. Chrysanthis. Scalable Processing of Read-Only Transactions in Broadcast Push. IEEE Conference on Distributed Computing and Systems, pp. 432-439, June 1999.

· S. Mazumdar and P. K. Chrysanthis. Achieving Consistency in Mobile Databases through Localization in PRO-MOTION. The 10th DEXA Workshop on Mobility in Databases and Distributed Systems, pp. 92-89, Aug. 1999.

Area Background

Several exciting advances in mobile computers and wireless technology have made database access by mobile computer users possible anywhere and at anytime. This, in turn, is enabling the development of an unprecedented number of new database applications that are not only affecting the way that we compute but, more significantly, they are changing the way we do business. Mobile and wireless computing facilitates more collaborative activities as well as opens enormous possibilities for information and data sharing.

However, the network and system assumptions underlying the traditional approach to distributed data management are no longer applicable in these new mobile database applications. For example, greater mobility implies a higher rate of spurious disconnection, and portability suggests more accidental disruptions. In contrast to traditional assumptions, disconnections in mobile environments do not necessarily imply failure of the disconnected mobile computer. The part of a computation executing on a mobile computer should be able to continue while the mobile computer is moving and not connected to the network. In these new mobile, distributed environments, therefore, it is important to study the issues of data consistency and sharing, and develop innovative methods that satisfy their requirements while overcoming the inherent limitations of mobile and wireless computing (e.g., frequent disconnection, limited battery life, restricted storage capacity, and low-bandwidth wireless network links).

Area References

· T. Imielinski and B. R. Badrinath. Mobile Wireless Computing: Challenges in Data Management. Communications of ACM, 37(10):18-28, Oct. 1994.

· T. Imielinski and H. Korth, Editors. Mobile Computing, Kluwer Academic Publishers, 1996. .

· K. Ramamritham and P. K. Chrysanthis. Advances in Concurrency Control and Transaction Processing, IEEE Computer Society Press, 1997.

· E. Pitoura and G. Samaras. Mobile Data Management, Kluwer Academic Publishers, 1998.

Potential Related Projects

Crafting Recovery for Advanced Transaction Models and Applications: Mobile transactions are instances of advanced transaction models.

Transaction Management in Multidatabase Systems: One can view mobile data management system as a special case of a multidatabase system. For example, the notion of local autonomy in mobile environments is manifested in the ability of mobile computers to continue to operate in an independent fashion when disconnected.

Distributed Constraint Maintenance: Efficient maintenance of integrity constraints that will require little, if any, coordination between mobile computers and database servers, will both facilitate disconnected operations as well as reduce the cost of communication during periods of adequate network connection.

Mobile computers and wireless networks are becoming an integral part of distributed computing environments which means that there is great potential for collaboration with projects focusing on wide-area database systems and heterogeneous and semi-structured data management.