Yannis E. Ioannidis

Research Interests

My research primarily focuses on two areas of database systems: optimization of complex queries and database support for scientific data.

Future database applications pose several new challenges to query optimization. The complexity of queries asked will be significantly higher than in traditional systems. The number of alternative evaluation algorithms will be much higher as well, especially with the use of parallelism or with attempts to optimize for several values of run-time parameters (parametric query optimization). Thus, the number of alternative access plan for processing a query will be extremely large, so that the currently used algorithms for finding the optimum among them will be inadequate. My research investigates the use of randomized optimization algorithms as a viable solution to this problem. I am primarily interested in simulated annealing and genetic algorithms, as well as other alternatives that take advantage of special properties of query optimization. I am also looking into complex query scheduling problems, especially those that arise in parallel and multimedia environments. Error propagation of size and cost estimates in complex queries are also part of my studies, where I am trying to identify the appropriate information that must be maintained by a database system to limit the propagation of error. To that end, I'm primarily focusing on identifying the properties of optimal histograms that approximate the distribution of values in relation attributes.

The computational mode of investigation is expected to be part of many experiments in various scientific disciplines in the future. The databases to be generated need specialized support on many aspects that current technology is not ready to provide. I am involved in the development of the ZOO Desktop Experiment Management Environment that will help scientists throughout the life cycle of their experimental studies. A primary component of that system will be a database system. Two major issues that my work addresses are visual user interfaces and semantic heterogeneity. In the former, I'm concentrating on identifying what the right metaphors are for representing complex database schemas, queries, and objects to scientists so that they are natural to them, and also on investigating the power of dynamic visual queries. In the latter, I'm concentrating on developing visual tools that will facilitate translation and integration of different data formats or schemas. Although these issues are generic and arise in all experimental scientific disciplines, my efforts are guided by the needs of specific projects with which I am associated, in particular, simulation-based performance studies of computer systems, simulation-based modeling of plant growth, NMR spectroscopy, DNA sequencing, and microscopic imaging.

Recent Publications

• Y. Ioannidis, "Query Optimization", ACM Computing Surveys, symposium issue on the 50th Anniversary of ACM, Vol. 28, No. 1, March 1996, pp. 121-123.
• M. Garofalakis and Y. Ioannidis, "Scheduling Issues in Multimedia Query Optimization", ACM Computing Surveys, symposium issue on Multimedia Systems, Vol. 27, No. 4, December 1995, pp. 590-592.
• Y. Ioannidis and R. Ramakrishnan, "Containment of Conjunctive Queries: Beyond Relations As Sets", ACM Transactions on Database Systems (TODS), Vol. 20, No. 3, September 1995, pp. 288-324.
• E. Haber, Y. Ioannidis, and M. Livny, "Foundations of Visual Metaphors for Schema Display", Journal of Intelligent Information Systems, Vol. 3, No. 3/4, July 1994, pp. 263-298. (Special issue on Visual Information Systems.)
• Y. Ioannidis and M. Tsangaris, "The Design, Implementation, and Performance Evaluation of BERMUDA", IEEE Transactions on Knowledge and Data Engineering (TKDE), Vol. 6, No. 1, February 1994, pp. 38-56.
• R. Miller, Y. Ioannidis, and R. Ramakrishnan, "Translation and Integration of Heterogeneous Schemas: Bridging the Gap between Theory and Practice", Information Systems, Vol. 19, No. 1, January 1994, pp. 3-31.
• Y. Ioannidis and S. Christodoulakis, "Optimal Histograms for Limiting Worst-Case Error Propagation in the Size of Join Results", ACM Transactions on Database Systems (TODS), Vol. 18, No. 4, December 1993, pp. 709-748.
• Y. Ioannidis, R. Ramakrishnan, and L. Winger, "Transitive Closure Algorithms Based on Graph Traversal", ACM Transactions on Database Systems (TODS), Vol. 18, No. 3, September 1993, pp. 512-576.
• Y. Ioannidis, "Dynamic Information Visualization", ACM Sigmod Record, Vol. 24, No. 4, December 1996.
• Y. Ioannidis and V. Poosala, "Histogram-Based Solutions to Diverse Database Estimation Problems", IEEE Data Engineering, Vol. 18, No. 3, September 1995, pp. 10-18.
• Y. Ioannidis, M. Livny, S. Gupta, and N. Ponnekanti, "ZOO: A Desktop Experiment Management Environment", Proc. 22nd International VLDB Conference, Bombay, India, September 1996, pp. 274-285.
• V. Poosala and Y. Ioannidis, "Estimation of Query-Result Distribution and its Application in Parallel-Join Load Balancing", Proc. 22nd International VLDB Conference, Bombay, India, September 1996, pp. 448-459.
• V. Anjur, Y. Ioannidis, and M. Livny, "Frog and Turtle: Visual Bridges Between Files and Object-Oriented Data", Proc. 8th International Conference on Scientific and Statistical Database Management, Stockholm, Sweden, June 1996, pp. 76-85.
• M. Garofalakis and Y. Ioannidis, "Multi-Dimensional Resource Scheduling for Parallel Queries", Proc. 1996 International ACM SIGMOD Conference, Montreal, Canada, May 1996, pp. 365-376.
• V. Poosala, Y. Ioannidis, P. Haas, and E. Shekita, "Improved Histograms for Selectivity Estimation of Range Predicates", Proc. 1996 International ACM SIGMOD Conference, Montreal, Canada, May 1996, pp. 294-305.
• Y. Ioannidis, M. Livny, J. Bao, and E. Haber, "User-Oriented Visual Layout at Multiple Granularities", Proc. 3nd International Workshop on Advanced Visual Interfaces, Gubbio, Italy, May 1996, pp. 184-193.
• E. Haber, Y. Ioannidis, and M. Livny, "OPOSSUM: Desk-Top Schema Management through Customizable Visualization", Proc. 21st International VLDB Conference, Zurich, Switzerland, September 1995, pp. 527-538.
• Y. Ioannidis and V. Poosala, "Balancing Histogram Optimality and Practicality for Query Result Size Estimation", Proc. 1995 International ACM SIGMOD Conference\fP, San Jose, CA, May 1995, pp. 233-244.
• O. Tsatalos, M. Solomon, and Y. Ioannidis, "The GMAP: A Versatile Tool for Physical Data Independence", Proc. 20th International VLDB Conference, Santiago, Chile, September 1994.
• O. Tsatalos and Y. Ioannidis, "A Unified Framework for Indexing in Database Systems", Proc. 4th International DEXA Conference, Athens, Greece, September 1994.
• Y. Ioannidis and M. Lashkari, "Incomplete Path Expressions and their Disambiguation", Proc. 1994 International ACM SIGMOD Conference, Minneapolis, MN, May 1994, pp. 138-149.
• E. Haber, Y. Ioannidis, and M. Livny, "OPOSSUM: A Flexible Schema Visualization and Editing Tool", Proc. 1994 ACM CHI Conference, Boston, MA, April 1994.
• R. Miller, Y. Ioannidis, and R. Ramakrishnan, "Translation and Integration of Heterogeneous Schemas: Bridging the Gap between Theory and Practice", Proc. 4th International EDBT Conference, Cambridge, England, March 1994, pp. 73-80.
• Y. Ioannidis, "Universality of Serial Histograms", Proc. 19th International VLDB Conference, Dublin, Ireland, August 1993, pp. 256-267.
• R. Miller, Y. Ioannidis, and R. Ramakrishnan, "The Use of Information Capacity in Schema Integration and Translation", Proc. 19th International VLDB Conference, Dublin, Ireland, August 1993, pp. 120-133.
• J. Wiener and Y. Ioannidis, "A Moose and a Fox Can Aid Scientists with Data Management Problems", Proc. 4th International Workshop on Database Programming Languages, New York, NY, August 1993.