Partial Grounded Fixpoints

Approximation fixpoint theory (AFT) is an algebraical study of fixpoints of lattice operators. Recently, AFT was extended with the notion of a grounded fixpoint. This type of fixpoint formalises common intuitions from various application domains of AFT, including logic programming, default logic, autoepistemic logic and abstract argumentation frameworks. The study of groundedness was limited to exact lattice points; in this paper, we extend it to the bilattice: for an approximator A of O, we define A-groundedness. We show that all partial Astable fixpoints are A-grounded and that the Awell-founded fixpoint is uniquely characterised as the least precise A-grounded fixpoint. We apply our theory to logic programming and study complexity.

Authors

• Bart Bogaerts KU Leuven, Belgium Vrije Universiteit Brussel, Belgium
• Joost Vennekens
• Marc Denecker KU Leuven

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