Convergence (logic)

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In mathematics, computer science and logic, convergence is the idea that different sequences of transformations come to a conclusion in a finite amount of time (the transformations are terminating), and that the conclusion reached is independent of the path taken to get to it (they are confluent).

More formally, a preordered set of term rewriting transformations are said to be convergent if they are confluent and terminating. [1]

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Confluence (abstract rewriting)

In computer science, confluence is a property of rewriting systems, describing which terms in such a system can be rewritten in more than one way, to yield the same result. This article describes the properties in the most abstract setting of an abstract rewriting system.

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Orthogonality as a property of term rewriting systems describes where the reduction rules of the system are all left-linear, that is each variable occurs only once on the left hand side of each reduction rule, and there is no overlap between them.

In mathematics, in the theory of rewriting systems, Newman's lemma, also commonly called the diamond lemma, states that a terminating abstract rewriting system (ARS), that is, one in which there are no infinite reduction sequences, is confluent if it is locally confluent. In fact a terminating ARS is confluent precisely when it is locally confluent.

In computer science, termination analysis is program analysis which attempts to determine whether the evaluation of a given program halts for each input. This means to determine whether the input program computes a total function.

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In computer science, a computation is said to diverge if it does not terminate or terminates in an exceptional state. Otherwise it is said to converge. In domains where computations are expected to be infinite, such as process calculi, a computation is said to diverge if it fails to be productive.

In mathematical logic and theoretical computer science, an abstract rewriting system is a formalism that captures the quintessential notion and properties of rewriting systems. In its simplest form, an ARS is simply a set together with a binary relation, traditionally denoted with ; this definition can be further refined if we index (label) subsets of the binary relation. Despite its simplicity, an ARS is sufficient to describe important properties of rewriting systems like normal forms, termination, and various notions of confluence.

Critical pair (logic)

In mathematical logic, a critical pair arises in term rewriting systems where rewrite rules overlap to yield two different terms. In more detail, is a critical pair if there is a term t for which two different applications of a rewrite rule yield the terms t1 and t2.

References

  1. Franz Baader; Tobias Nipkow (1998). Term Rewriting and All That. Cambridge University Press. ISBN   0-521-77920-0.