Updates and view maintenance in soft real-time database systems

ABSTRACT

A database system contains base data items which record and model a physical, real world environment. For better decision support, base data items are summarized and correlated to derive views. These base data and views are accessed by application transactions to generate the ultimate actions taken by the system. As the environment changes, updates are applied to the base data, which subsequently trigger view recomputations. There are thus three types of activities: base data update, view recomputation, and transaction execution. In a real-time system, two timing constrains need to be enforced. We require transactions meet their deadlines (transaction timeliness) and read fresh data (data timeliness). In this paper we define the concept of absolute and relative temporal consistency from the perspective of transactions. We address the important issue of transaction scheduling among the three types of activities such that the two timing requirements can be met. We also discuss how a real-time database system should be designed to enforce different levels of temporal consistency.

REFERENCES

• 1: Robert K. Abbott , Hector Garcia-Molina, Scheduling Real-time Transactions: a Performance Evaluation, Proceedings of the 14th International Conference on Very Large Data Bases, p.1-12, August 29-September 01, 1988
• 2: B. Adelberg , H. Garcia-Molina , B. Kao, Applying update streams in a soft real-time database system, Proceedings of the 1995 ACM SIGMOD international conference on Management of data, p.245-256, May 22-25, 1995, San Jose, California, United States
• 3: Brad Adelberg , Ben Kao , Hector Garcia-Molina, Database Support for Efficiently Maintaining Derived Data, Proceedings of the 5th International Conference on Extending Database Technology: Advances in Database Technology, p.223-240, March 25-29, 1996
• 4: Munir Cochinwala , John Bradley, A Multidatabase System for Tracking and Retrieval of Financial Data, Proceedings of the 20th International Conference on Very Large Data Bases, p.714-721, September 12-15, 1994
• 5: B. Kao et. al. Updates and view maintenance in soft real-time database systems. Technical Report TR-99-06, University of Hong Kong, 1999. URL: http: } / www. csis.hku .hk / publications.
• 6: Bhaskar Purimetla , Rajendran M. Sivasankaran , Krithi Ramamritham , John A. Stankovic, Real-time databases: issues and applications, Advances in real-time systems, Prentice-Hall, Inc., Upper Saddle River, NJ, 1995
• 7: Young-Kuk Kim , Sang H. Son, Predictability and consistency in real-time database systems, Advances in real-time systems, Prentice-Hall, Inc., Upper Saddle River, NJ, 1995
• 8: T. W. Kuo and A. K. Mok. SSP: A semanticsbased protocol for real-time data access. In IEEE Real-Time Systems Symposium, pages 76-86, 1993.
• 9: Mesquite Software, Inc. C$IM 18 User Guide. URL: http://www.mesquite.com.
• 10: Gultekin Ozsoyoglu , Richard Thomas Snodgrass, Temporal and Real-Time Databases: A Survey, IEEE Transactions on Knowledge and Data Engineering, v.7 n.4, p.513-532, August 1995 [doi>10.1109/69.404027]
• 11: Krithi Ramamritham, Real-time databases, Distributed and Parallel Databases, v.1 n.2, p.199-226, April 1993 [doi>10.1007/BF01264051]
• 12: Xiaohui (Carol) Song , Jane W. S. Liu, Maintaining Temporal Consistency: Pessimistic vs. Optimistic Concurrency Control, IEEE Transactions on Knowledge and Data Engineering, v.7 n.5, p.786-796, October 1995 [doi>10.1109/69.469820]
• 13: Ming Xiong , R. Sivasankaran , J. A. Stankovic , K. Ramamritham , D. Towsley, Scheduling transactions with temporal constraints: exploiting data semantics, Proceedings of the 17th IEEE Real-Time Systems Symposium (RTSS '96), p.240, December 04-06, 1996
• 14: P.S. Yu, K.L. Wu, K.J. Lin, and S.H. Son. On realtime databases: Concurrency control and scheduling. Proceedings of the iEEE, 82(1):140-157, 1994.

INDEX TERMS

Primary Classification:
  H. Information Systems
  H.2 DATABASE MANAGEMENT

Additional Classification:
  H. Information Systems
  H.3 INFORMATION STORAGE AND RETRIEVAL
      H.3.4 Systems and Software
          Subjects: Performance evaluation (efficiency and effectiveness)

General Terms:
Design, Management, Measurement, Performance, Reliability, Theory

Keywords:
real-time database, temporal consistency, transaction scheduling, updates, view maintenance