Abstract not found

We introduce a class of restrictions for the ordered paramodulation and superposition calculi (inspired by the basic strategy for narrowing), in which paramodulation inferences are forbidden at terms introduced by substitutions from previous inference steps. In addition we introduce restrictions based on term selection rules and redex orderings, which are general criteria for delimiting the terms which are available for inferences. These refinements are compatible with standard ordering restrictions and are complete without paramodulation into variables or using functional reflexivity axioms. We prove refutational completeness in the context of deletion rules, such as simplification by rewriting (demodulation) and subsumption, and of techniques for eliminating redundant inferences.

this paper is to show how to solve the constraints that are involved in the deduction mechanism of the first part. This may be interesting in its own since this provides with a unification algorithm for an order-sorted logic with context variables and can be read independently of the first part. This can also be compared with unification of term schemes of various kind (Chen & Hsiang, 1991; Salzer, 1992; Comon, 1995; R. Galbav'y and M. Hermann, 1992). Indeed,

Conditional rewriting has been studied both from the point of view of algebraic data type specifications and as a computational paradigm combining logic and functional programming. An important issue, in either case, is determining whether a rewrite system has the Church-Rosser, or confluence, property. In this paper, we settle negatively the question whether "joinabihty of critical pairs" is, in general, sufficient for confluence of terminating conditional systems. We review known sufficient conditions for confluence, and also prove two new positive results for systems having critical pairs and arbitrarily big terms in conditions.

Abstract not found

Recently well-quasi orders in general, and homeomorphic embedding in particular, have gained popularity to ensure the termination of program analysis, specialisation and transformation techniques. In this paper,

Type systems for operations on extensible records form a foundation for statically typed languages addressing some aspects of object oriented programming and database applications. A number of primitive operations have been proposed: extending a record with a new field, overwriting an existing field, removing a field, and various kinds of concatenation. We show here that a record calculus based on a symmetric concatenation operator, where two records may be concatenated only if they have no overlapping fields, also captures the types of many other useful primitive record operations. "Mergeability constraints" are expressed directly using explicit annotations on type variables and constrained second-order type quantification instead of a rule of subsumption; we argue that the resulting system is more straightforward than subsumption-based alternatives. This research was supported in part by the Office of Naval Research and in part by the Defense Advanced Research Projects Agency (DOD), ...

In this paper we introduce and study a new lambda-calculus with explicit substitution, lambda-xgc, which has two distinguishing features: first, it retains the use of traditional variable names, specifying terms modulo renaming; this simplifies the reduction system. Second, it includes reduction rules for explicit garbage collection; this simplifies several proofs. We show that lambda-xgc is a conservative extension which preserves strong normalisation (PSN) of the untyped lambda-calculus. The result is obtained in a modular way by first proving it for garbage-free reduction and then extending to `reductions in garbage'. This provides insight into the counterexample to PSN for lambda-sigma of Melliès (1995); we exploit the abstract nature of lambda-xgc to show how PSN is in conflict with any reasonable substitution composition rule (except for trivial composition rules of which we mention one). Key words: lambda calculus, explicit substitution, strong normalisation, garbage collection.

Abstract not found

This paper gives methods for statically analyzing sets of active database rules to determine if the rules are (1) guaranteed to terminate, (2) guaranteed to produce a unique final database state, and (3) guaranteed to produce a unique stream of observable actions. If the analysis determines that one of these properties is not guaranteed, it isolates the rules responsible for the problem and determines criteria that, if satisfied, guarantee the property. The analysis methods are presented in the context of the Starburst Rule System. 1 Introduction Rules in active database systems allow specification of data manipulation operations that are executed automatically whenever certain events occur or conditions are met [DHW94,DW92,HW93]. Active database rules provide a general and powerful mechanism for many database features, including integrity constraint enforcement, derived data maintenance, triggers, alerters, authorization checking, and versioning. In addition, active database sy...