Modal definability of first-order formulas with free variables and query answering
We present an algorithmically efficient criterion of modal definability for first-order existential conjunctive formulas with several free variables. Then we apply it to establish modal definability of some family of first-order for all there exists-formulas. Finally, we use our definability results to show that, in any expressive description logic, the problem of answering modally definable conjunctive queries is polynomially reducible to the problem of knowledge base consistency. (C) 2013 Elsevier B.V. All rights reserved.
modal definability description logic conjunctive query knowledge base modal logic correspondence theory