# Solving Query-answering Problems with If-and-Only-If Formulas

### Kiyoshi Akama, Ekawit Nantajeewarawat

#### Abstract

A query-answering problem (QA problem) is concerned with finding all ground instances of a query atomic formula that are logical consequences of a given logical formula describing the background knowledge of the problem. A method for solving QA problems on full first-order logic has been invented based on the equivalent transformation (ET) principle, where a given QA problem on first-order logic is converted into a QA problem on extended clauses and is then further transformed repeatedly and equivalently into simpler forms until its answer set can be readily obtained. In this paper, such a clause-based solution is extended by proposing a new method for effectively utilizing a universally quantified if-and-only-if statement defining a predicate, which is called an iff-formula. The background knowledge of a given QA problem is separated into two parts: (i) a conjunction of iff-formulas and (ii) other types of knowledge. Special ET rules for manipulating iffformulas are introduced. The new solution method deals with both iff-knowledge in first-order logic and a set of extended clauses. Application of this solution method is illustrated.

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#### Paper Citation

#### in Harvard Style

Akama K. and Nantajeewarawat E. (2014). **Solving Query-answering Problems with If-and-Only-If Formulas** . In *Proceedings of the International Conference on Knowledge Engineering and Ontology Development - Volume 1: KEOD, (IC3K 2014)* ISBN 978-989-758-049-9, pages 333-344. DOI: 10.5220/0005097903330344

#### in Bibtex Style

@conference{keod14,

author={Kiyoshi Akama and Ekawit Nantajeewarawat},

title={Solving Query-answering Problems with If-and-Only-If Formulas},

booktitle={Proceedings of the International Conference on Knowledge Engineering and Ontology Development - Volume 1: KEOD, (IC3K 2014)},

year={2014},

pages={333-344},

publisher={SciTePress},

organization={INSTICC},

doi={10.5220/0005097903330344},

isbn={978-989-758-049-9},

}

#### in EndNote Style

TY - CONF

JO - Proceedings of the International Conference on Knowledge Engineering and Ontology Development - Volume 1: KEOD, (IC3K 2014)

TI - Solving Query-answering Problems with If-and-Only-If Formulas

SN - 978-989-758-049-9

AU - Akama K.

AU - Nantajeewarawat E.

PY - 2014

SP - 333

EP - 344

DO - 10.5220/0005097903330344