On the Feasibility of Informative Answers
In this chapter, we investigate the situation where a user’s request for data cannot be answered in the desired way because the data base does not contain the data requested. We argue that in such a situation it is not sufficient to report to the user the fact that the query failed, without providing the deeper reasons for the failure; an informative answer to a failing query, however, will adjust the user’s wrong assumptions about the contents of the data base and often will free him/her from the need of asking additional queries. We describe a formal method by means of which the reasons for the failure of a user’s query expressed in a relational calculus based language may be inferred and reported to the user as answer; special attention is paid to the amount of computation required for this answer generation procedure. We then show that a wide class of integrity constraints of a data base may be used to further improve the inference process and that any abuse of informative answers for the deduction of confidential information may be prevented easily.
KeywordsIntegrity Constraint Confidential Information Original Query Closed World Assumption Qualification Expression
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- 3.Codd, E. F. [1971a] “Relational Completeness of Data Base Sublanguages.” In Courant Computer Science Symposia, Vol 6, Data Base Systems (R. Rustin, Ed.) Prentice Hall, Englewood Cliffs, New Jersey, 1972.Google Scholar
- 5.Date, C. J.  An Introduction to Database Systems, Addison-Wesley Publishing Co., Reading Mass., 1975.Google Scholar
- 7.Demolombe, R. [1979b] “Assigning Meaning to Ill-defined Queries Expressed in Predicate Calculus Language.” In Preprints of the Workshop on Formal Bases for Data Bases. Toulouse, 1979, 21.1–21.26.Google Scholar
- 9.Janas, J. M. [1979a] “How to not Say Nil — Improving Answers to Failing Queries in Data Base Systems.” In Proc. 6th Int. Joint Conf. on Artificial Intelligence. Tokyo, 1979, 429–434.Google Scholar
- 11.Kaplan, S. J.  “Cooperative Responses from a Portable Natural Language Data Base Query System.” Ph.D. Thesis, Dept. of Computer and Information Sciences, University of Pennsylvania, 1979.Google Scholar
- 12.Lee, R. M. [1978a] “Conversational Aspects of Database Interactions.” In Proc. 4th Int. Conf. on Very Large Data Bases. Berlin, 1978, 392–399.Google Scholar
- 13.Lee R. M. [1978b] “Algorithmic Analysis for Informative Failure in the Relational Calculus.” Working Paper 78–10–08, Dept. of Decision Sciences, University of Pennsylvania, 1978.Google Scholar
- 14.McSkimin, J. R. and J. Minker  “The Use of a Semantic Network in a Deduction Question Answering System.” In Proc. 5th Int. Joint Conf. on Artificial Intelligence. Cambridge, MA, 1977, 50–58.Google Scholar
- 15.Reiter, R.  “On Closed World Data Bases.” In Logic and Data Bases (H. Gallaire and J. Minker, Eds.) Plenum Press, New York, 1978, 55–76.Google Scholar
- 16.Reiter, R.  “On the Integrity of Typed First Order Data Bases.” In Advances in Data Base Theory — Volume 1, (H. Gallaire, J. Minker and J. M. Nicolas, Eds.), Plenum Press, New York, 1981, 137–157.Google Scholar