A many-sorted calculus based on resolution and paramodulation

The first-order calculus whose well formed formulas are clauses and whose sole inference rules are factorization, resolution and paramodulation is extended to a many-sorted calculus. As a basis for Automated Theorem Proving, this many-sorted calculus leads to a remarkable reduction of the search space and also to simpler proofs. Soundness and completeness of the new calculus and the Sort-Theorem, which relates the many-sorted calculus to its one-sorted counterpart, are shown. In addition results about term rewriting and unification in a many-sorted calculus are obtained. The practical consequences for an implementation of an automated theorem prover based on the many-sorted calculus are described

Recasting Cohn\u27s many sorted logic into a constrained logic

The use of a many sorted logic for theorem proving carries many advantages over a traditional unsorted logic. By placing restrictions on the search space, a many sorted logic can significantly reduce the amount steps in the resolution process. However, as a logic becomes more efficient, it increases in complexity. One of these efficient log ics is Cohn\u27s Many Sorted Logic, LLAMA. It uses complex data structures such as the sort lattice and sort arrays to maintain information about the sorts. Recasting LLAMA into Bürckert\u27s constrained logic will keep the functionality of LLAMA while using a format that reduces the complexity and maintains a more traditional resolution rule

A Many-Sorted Calculus with Polymorphic Functions Based On Resolution And Paramodulation

A many-sorted first order calculus, called ΣRP, whose well formed formulas are sorted (typed) clauses and whose inference rules are factorization, resolution, paramodulation and weakening is extended to a many sorted calculus ΣRP* with polymorphic functions (overloading). It is assumed that the sort structure is a finite partially ordered set with a greatest element. It is shown, that this extended calculus is sound and complete, provided the functional reflexivity axioms are present. It is also shown, that unification of terms containing polymorphic functions is in general finitary, i.e. the set of most general unifiers may contain more than one element, but at most finitely many. We give a natural condition for the signature (the sort structure), such that the set of most general unifiers is always at most a singleton provided this condition holds

Ein mehrsortiger Resolutionskalkül mit Paramodulation

Der Resolutionskalkül mit Paramodulationsregel wird zu einem mehrsortigen Kalkül erweitert. Als Grundlage für das automatische Beweisen erhält man mit diesem Kalkül einen stark reduzierten Suchraum und einfachere Beweise. Die Vollständigkeit, die Korrektheit und der Sortensatz, der den neuen Kalkül mit seinem einsortigen Gegenstück in Beziehung setzt, werden bewiesen. Ergebnisse über Grundtermersetzungen und Unifikation in einem mehrsortigen Kalkül werden vorgestellt. Die Implementierung eines automatischen Beweisers für den neuen Kalkül wird beschrieben. Die Vorteile der Methode werden anhand ausgewählter Beispiele belegt.The resolution calculus with paramodulationrule is extended to a many-sorted calculus. As a basis for Automated Theorem Proving, this many-sorted calculus leads to a remarkable reduction of the search space and also to simpler proofs. Soundness and completeness of the new calculus and the Sort-Theorem, which relates the many-sorted calculus to its one-sorted counterpart, are shown. In addition results about groundterm rewriting and unification in a many-sorted calculus are obtained. The practical consequences for an implementation of an automated theorem prover based on the many-sorted calculus are described. The advantages of the proposed method is verified by certain examples

A resolution principle for clauses with constraints

We introduce a general scheme for handling clauses whose variables are constrained by an underlying constraint theory. In general, constraints can be seen as quantifier restrictions as they filter out the values that can be assigned to the variables of a clause (or an arbitrary formulae with restricted universal or existential quantifier) in any of the models of the constraint theory. We present a resolution principle for clauses with constraints, where unification is replaced by testing constraints for satisfiability over the constraint theory. We show that this constrained resolution is sound and complete in that a set of clauses with constraints is unsatisfiable over the constraint theory if we can deduce a constrained empty clause for each model of the constraint theory, such that the empty clauses constraint is satisfiable in that model. We show also that we cannot require a better result in general, but we discuss certain tractable cases, where we need at most finitely many such empty clauses or even better only one of them as it is known in classical resolution, sorted resolution or resolution with theory unification

Hierarchic Superposition Revisited

Many applications of automated deduction require reasoning in first-order logic modulo background theories, in particular some form of integer arithmetic. A major unsolved research challenge is to design theorem provers that are "reasonably complete" even in the presence of free function symbols ranging into a background theory sort. The hierarchic superposition calculus of Bachmair, Ganzinger, and Waldmann already supports such symbols, but, as we demonstrate, not optimally. This paper aims to rectify the situation by introducing a novel form of clause abstraction, a core component in the hierarchic superposition calculus for transforming clauses into a form needed for internal operation. We argue for the benefits of the resulting calculus and provide two new completeness results: one for the fragment where all background-sorted terms are ground and another one for a special case of linear (integer or rational) arithmetic as a background theory

Clastic Polygonal Networks Around Lyot Crater, Mars: Possible Formation Mechanisms From Morphometric Analysis

Polygonal networks of patterned ground are a common feature in cold-climate environments. They can form through the thermal contraction of ice-cemented sediment (i.e. formed from fractures), or the freezing and thawing of ground ice (i.e. formed by patterns of clasts, or ground deformation). The characteristics of these landforms provide information about environmental conditions. Analogous polygonal forms have been observed on Mars leading to inferences about environmental conditions. We have identified clastic polygonal features located around Lyot crater, Mars (50°N, 30°E). These polygons are unusually large (> 100 m diameter) compared to terrestrial clastic polygons, and contain very large clasts, some of which are up to 15 metres in diameter. The polygons are distributed in a wide arc around the eastern side of Lyot crater, at a consistent distance from the crater rim. Using high-resolution imaging data, we digitised these features to extract morphological information. These data are compared to existing terrestrial and Martian polygon data to look for similarities and differences and to inform hypotheses concerning possible formation mechanisms. Our results show the clastic polygons do not have any morphometric features that indicate they are similar to terrestrial sorted, clastic polygons formed by freeze-thaw processes. They are too large, do not show the expected variation in form with slope, and have clasts that do not scale in size with polygon diameter. However, the clastic networks are similar in network morphology to thermal contraction cracks, and there is a potential direct Martian analogue in a sub-type of thermal contraction polygons located in Utopia Planitia. Based upon our observations, we reject the hypothesis that polygons located around Lyot formed as freeze-thaw polygons and instead an alternative mechanism is put forward: they result from the infilling of earlier thermal contraction cracks by wind-blown material, which then became compressed and/or cemented resulting in a resistant fill. Erosion then leads to preservation of these polygons in positive relief, while later weathering results in the fracturing of the fill material to form angular clasts. These results suggest that there was an extensive area of ice-rich terrain, the extent of which is linked to ejecta from Lyot crater