Learning elementary formal systems with queries

  • Authors:
  • Hiroshi Sakamoto;Kouichi Hirata;Hiroki Arimura

  • Affiliations:
  • Department of Informatics, Kyushu University, Hakozaki 6-10-1, Fukuoka 812-8581, Japan;Department of Artificial Intelligence, Kyushu Institute of Technology, Kawazu 680-4, Iizuka 820-8502, Japan;Department of Informatics, Kyushu University, Hakozaki 6-10-1, Fukuoka 812-8581, Japan and PRESTO, Japan Science and Technology Co., Japan

  • Venue:
  • Theoretical Computer Science - Selected papers in honour of Setsuo Arikawa
  • Year:
  • 2003

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Abstract

The elementary formal system (EFS) is a kind of logic programs which directly manipulates strings, and the learnability of the subclass called hereditary EFSs (HEFSs) has been investigated in the frameworks of the PAC-learning, query-learning, and inductive inference models. The hierarchy of HEFS is expressed by HEFS(m,k,t,r), where m, k, t and r denote the number of clauses, the occurrences of variables in the head, the number of atoms in the body, and the arity of predicate symbols. The present paper deals with the learnability of HEFS in the query learning model using equivalence queries and additional queries such as membership, predicate membership, entailment membership, and dependency queries. We show that the class HEFS(*, k, t, r) is polynomial-time learnable with the equivalence and predicate membership queries and the class HEFS(*,k,*,r) with termination property is polynomial-time learnable with the equivalence, entailment membership, and dependency queries for the unbounded parameter *. A lowerbound on the number of queries is presented. We also show that the class HEFS(*,k,t,r) is hard to learn with the equivalence and membership queries under the cryptographic assumptions. Furthermore, the learnability of the class of unions of regular pattern languages, which is a subclass of HEFSs, is investigated. The bounded unions of regular pattern languages are polynomial-time predictable with membership query. However, all unbounded unions of regular pattern languages are not polynomial-time predictable with membership queries if neither are the DNF formulas.