# On finding the optimal access path to resolve a relational data base query

## Abstract

The paper presents a formal model to specify a data base, a query and the access path which must be followed to obtain the ansewer. The model is based on the problem reduction hypergraphs, for which an admissible and optimal search algorithm is known. An effective method is given to map the data base and the query into a problem reduction hypergraph, which the known search algorithm can be applied to. The optimal solution to the problem reduction hypergraph provides an optimal (and possibly parallel) program to obtain the answer to the given query. Since the model allows to determine the correct answer, if any, without modifications of the data base nor requiring further information, it is an improvement over the models presented in the literature.

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## References

- /CK/.Carlson, C.R., and Kaplan, R.S. A generalized access path model and its application to a relational data base system. Proc. ACM-SIGMOD Int. Conf. on Management of Data 1976, Washington, D.C., USA, pp. 143–154.Google Scholar
- /TL/.Tsichritzis, D.C., and Lochovski, F.H. Data Base Management Systems. Academic Press, New York (1977).Google Scholar
- /LS1/.Levi, G., and Sirovich, F. A problem reduction model for non independent subproblems. Proc. 4th Int. Joint Conf. on Artif. Intel. 1975, Tbilisi, GSSR, USSR, pp. 340–344.Google Scholar
- /LS2/.Levi, G., and Sirovich, F. Generalized And/Or graphs. Artificial Intelligence, 7 (1976), pp. 243–259.Google Scholar
- /BE/.Berge, C. Graphes et Hypergraphes. Dunod, Paris (1970).Google Scholar
- /CB/.Chamberlin, D.D., and Boyce, R.F. SEQUEL: A structured English query language, Proc. ACM-SIGMOD Workshop on Data Description, Access and Control 1974, pp. 249–264.Google Scholar
- /HA/.Hanani, M.Z. An optimal evaluation of boolean expressions in an online query system, CACM 20, 5 (1977), pp. 344–347.Google Scholar
- /ES/.Eisner, M.J., and Severance, D.G. Mathematical techniques for efficient record segmentation in large shared data bases, J. ACM 23, 4 (1976), pp. 619–635.Google Scholar
- /KL/.Klar, P. Conditional answer in question-answering systems, 6th Proc. Int. Conf. on Artif. Intel. (1979). Tokyo.Google Scholar