A Three-Valued Semantics for Deductive Databases and Logic Programs

@article{You1994ATS,
  title={A Three-Valued Semantics for Deductive Databases and Logic Programs},
  author={Jia-Huai You and Li-Yan Yuan},
  journal={J. Comput. Syst. Sci.},
  year={1994},
  volume={49},
  pages={334-361}
}
This paper proposes two principles, justifiability and minimal undefinedness, for a threevalued model-theoretic approach to semantics of logic programs and deductive databases (also called disjunctive logic programs). The former is intimately related to the concept of labeling-based justification in Doyle's truth maintenance system while the latter requires the use of the truth value undefined only when it is necessary. We examine the question why and in what circumstances the undefined is… CONTINUE READING