We describe ongoing work on the use of subsumption to remove redundant inferences from propositional resolution refutation proofs of the style generated by conflict driven clause learning SAT solvers. This is used for faster LCF-style proof replay in interactive theorem provers. There may also be an application in the extraction of small unsatisfiable cores.

Negation is known to correlate with changes of word order, agreement, or case marking in the clause. I present data from Skou, a language of north-central New Guinea, which show obliques and adjuncts appearing postverbally in the SOV positive clause and preverbally in negative clauses. Moreover, in addition to these changes in the order of constituents, the grammatical functions assigned in the...

The development of clause learning has had a tremendous effect on the overall performance of SAT-Solvers. Clause learning has allowed SAT-Solvers to tackle industrial sized problems that formerly would have required impractical time scales. The development of techniques for efficient clause management and storage have also proved important in reducing some of the memory usage problems inherent ...

In this paper, we analyze the various philosophies to define a query language for geographical database. The differences among the three possibilities of extending the SQL language rely on the definition of the clause Select: (1) the clause Select does not accept a spatial operator and the Where clause accepts one (or several) predicate defined between attributes; (2) the clause Select accepts ...

This paper discusses the topic of the minimum width of a regular resolution refutation of a set of clauses. The main result shows that there are examples having small regular resolution refutations, for which any regular refutation must contain a large clause. This forms a contrast with corresponding results for general resolution refutations.

In this paper I propose a new analysis of the English cleft in which the cleft clause is a restrictive relative clause adjoined to the clefted XP. I provide evidence showing that both ‘matching’ and ‘raising’ derivations are possible, that the initial it of clefts is not an expletive, and that the cleft clause undergoes obligatory extraposition to VP. Taken together, this evidence favours the p...

This paper presents an efficient algorithm for computing sub-Herbrand universes for arguments of functions and predicates in a given clause set. Unlike the previous algorithm, which processes all clauses in the given clause set once for computing each sub-Herbrand universe, the proposed algorithm computes all sub-Herbrand universes in the clause set by processing each clause in the clause set o...