We prove that the problem of determining the minimum propositional proof length is NP- hard to approximate within a factor of 2 log1 - o (1)n. These results are very robust in that they hold for ...

A propositional system of modal logic is second-order if it contains quantifiers ∀p and ∃p, which, in the standard interpretation, are construed as ranging over sets of possible worlds (propositions).

In propositional logic, an atomic sentence is simple in the sense that it is not the result of composition from simpler sentences using the propositional connectives.

Description: Intelligent industrial systems. Expert-system and knowledge-based decision and control examples. Propositional logic, resolution principle for deduction, Horn-clause systems of logic, ...