Malicious Omissions and Errors in Answers to Membership Queries

  • Authors:
  • Dana Angluin;Mārtiņš Kriķis;Robert H. Sloan;György Turán

  • Affiliations:
  • Department of Computer Science, Yale University, P.O. Box 208285, New Haven, CT 06520. E-mail: angluin@cs.yale.edu, krikis@cs.yale.edu;Department of Computer Science, Yale University, P.O. Box 208285, New Haven, CT 06520. E-mail: angluin@cs.yale.edu, krikis@cs.yale.edu;Dept. of Electrical Eng. and Computer Science, 851 S. Morgan St. Rm 1120, University of Illinois at Chicago, Chicago, IL 60607. E-mail: sloan@eecs.uic.edu;Dept. of Math., Stat., and Comp. Sci., 851 S. Morgan St. Rm 322, University of Illinois at Chicago, Chicago, IL 60607, Automata Theory Research Group Hungarian Academy of Sciences, Szeged. E-mail: ...

  • Venue:
  • Machine Learning
  • Year:
  • 1997

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Abstract

We consider two issues in polynomial-time exact learning of conceptsusing membership and equivalence queries: (1) errors or omissions inanswers to membership queries, and (2) learning finite variants ofconcepts drawn from a learnable class.To study (1), we introduce two new kinds of membership queries:limited membership queries and malicious membership queries. Each isallowed to give incorrect responses on a maliciously chosen set ofstrings in the domain. Instead of answering correctly about astring, a limited membership query may give a special “I don‘tknow” answer, while a malicious membership query may give the wronganswer. A new parameter L is used to bound the length of anencoding of the set of strings that receive such incorrect answers.Equivalence queries are answered correctly, and learning algorithmsare allowed time polynomial in the usual parameters and L. Anyclass of concepts learnable in polynomial time using equivalence andmalicious membership queries is learnable in polynomial time usingequivalence and limited membership queries; the converse is an openproblem. For the classes of monotone monomials and monotone k-term DNF formulas, we present polynomial-time learning algorithms usinglimited membership queries alone. We present polynomial-timelearning algorithms for the class of monotone DNF formulas usingequivalence and limited membership queries, and using equivalence andmalicious membership queries.To study (2), we consider classes of concepts that are polynomiallyclosed under finite exceptions and a natural operation to addexception tables to a class of concepts. Applying this operation, weobtain the class of monotone DNF formulas with finite exceptions. Wegive a polynomial-time algorithm to learn the class of monotone DNFformulas with finite exceptions using equivalence and membershipqueries. We also give a general transformation showing that anyclass of concepts that is polynomially closed under finite exceptionsand is learnable in polynomial time using standard membership andequivalence queries is also polynomial-time learnable using maliciousmembership and equivalence queries. Corollaries include thepolynomial-time learnability of the following classes using maliciousmembership and equivalence queries: deterministic finite acceptors,boolean decision trees, and monotone DNF formulas with finiteexceptions.