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Generalized Sufficient Conditions for Modular Termination of Rewriting
 IN ENGINEERING, COMMUNICATION AND COMPUTING
, 1992
"... Modular properties of term rewriting systems, i.e. properties which are preserved under disjoint unions, have attracted an increasing attention within the last few years. Whereas confluence is modular this does not hold true in general for termination. By means of a careful analysis of potential cou ..."
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Cited by 49 (7 self)
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Modular properties of term rewriting systems, i.e. properties which are preserved under disjoint unions, have attracted an increasing attention within the last few years. Whereas confluence is modular this does not hold true in general for termination. By means of a careful analysis of potential counterexamples we prove the following abstract result. Whenever the disjoint union R1 \Phi R2 of two (finitely branching) terminating term rewriting systems R1 , R2 is nonterminating, then one of the systems, say R1 , enjoys an interesting (undecidable) property, namely it is not termination preserving under nondeterministic collapses, i.e. R1 \Phi fG(x; y) ! x; G(x; y) ! yg is nonterminating, and the other system R2 is collapsing, i.e. contains a rule with a variable right hand side. This result generalizes known sufficient criteria for modular termination of rewriting and provides the basis for a couple of derived modularity results. Furthermore, we prove that the minimal rank of pote...
Completeness of Combinations of Constructor Systems
 Journal of Symbolic Computation
, 1993
"... this paper we show that it is sufficient to impose the constructor discipline for obtaining the modularity of completeness. This result is a simple consequence of a quite powerful divide and conquer technique for establishing completeness of such constructor systems. Our approach is not limited to s ..."
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Cited by 31 (2 self)
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this paper we show that it is sufficient to impose the constructor discipline for obtaining the modularity of completeness. This result is a simple consequence of a quite powerful divide and conquer technique for establishing completeness of such constructor systems. Our approach is not limited to systems which are composed of disjoint parts. The importance of our method is that we may decompose a given constructor system into parts which possibly share function symbols and rewrite rules in order to infer completeness. We obtain a similar technique for semicompleteness, i.e. the combination of confluence and weak normalisation. 1. Introduction
Sufficient Conditions for Modular Termination of Conditional Term Rewriting Systems
 In Proceedings of the 3rd International Workshop on Conditional Term Rewriting Systems
, 1993
"... . Recently we have shown the following abstract result for unconditional term rewriting systems (TRSs). Whenever the disjoint union R1 \Phi R2 of two (finite) terminating TRSs R1 , R2 is nonterminating, then one of the systems, say R1 , enjoys an interesting property, namely it is not termination ..."
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Cited by 13 (4 self)
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. Recently we have shown the following abstract result for unconditional term rewriting systems (TRSs). Whenever the disjoint union R1 \Phi R2 of two (finite) terminating TRSs R1 , R2 is nonterminating, then one of the systems, say R1 , enjoys an interesting property, namely it is not termination preserving under nondeterministic collapses, i.e. R1 \Phi fG(x; y) ! x; G(x; y) ! yg is nonterminating, and the other system R2 is collapsing, i.e. contains a rule with a variable right hand side. This result generalizes known sufficient syntactical criteria for modular termination of rewriting. Here we extend this result and derived sufficient criteria for modularity of termination to the case of conditional term rewriting systems (CTRSs). Moreover we relate various definitions of notions related to termination of CTRSs to each other and discuss some subtleties and problems concerning extra variables in the rules. 1 Introduction From a theoretical point of view and also for efficiency ...
A structural analysis of modular termination of term rewriting systems
, 1991
"... Modular properties of term rewriting systems, i.e. properties which are preserved under disjoint unions, have attracted an increasing attention within the last few years. Whereas confluence is modular this does not hold true in general for termination. By result. Whenever the disjoint union R 1 \Phi ..."
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Cited by 9 (4 self)
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Modular properties of term rewriting systems, i.e. properties which are preserved under disjoint unions, have attracted an increasing attention within the last few years. Whereas confluence is modular this does not hold true in general for termination. By result. Whenever the disjoint union R 1 \Phi R 2 of two (finite) terminating term rewriting systems R 1, R 2 is nonterminating, then one of the systems, say R 1, enjoys an interesting (undecidable) property, namely it is not termination preserving under nondeterministic collapses, i.e. R 1 \Phi fG(x; y) ! x; G(x; y) ! yg is nonterminating, and the other system R 2 is collapsing, i.e. contains a rule with a variable right hand side. This result generalizes known sufficient syntactical criteria for modular termination of rewriting. Then we develop a specialized version of the `increasing interpretation method' for proving termination of combinations of term rewriting systems. This method is applied to establish modularity of termination for certain classes of term rewriting systems. In particular, termination turns out to be modular for the class of
Combinations of Simplifying Conditional Term Rewriting Systems
 In Proceedings of the 3rd International Workshop on Conditional Term Rewriting Systems
, 1992
"... . A conditional term rewriting system (CTRS) is called simplifying if there exists a simplification ordering ? on terms such that the lefthand side of any rewrite rule is greater than the righthand side and the terms occurring in the conditions of that rule. If a simplifying join CTRS consists of ..."
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Cited by 4 (2 self)
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. A conditional term rewriting system (CTRS) is called simplifying if there exists a simplification ordering ? on terms such that the lefthand side of any rewrite rule is greater than the righthand side and the terms occurring in the conditions of that rule. If a simplifying join CTRS consists of finitely many rules, it is terminating and the applicability of a rewrite rule is decidable by recursively reducing the terms in the conditions. Consider two finite CTRSs R1 and R2 which may share constructors (symbols that do not occur at the root position of the lefthand side of any rewrite rule) but no other function symbols. It will be shown that the combined CTRS R = R1[R2 is simplifying if and only if R1 and R2 are simplifying. Moreover, confluence is a modular property of finite simplifying join CTRSs. 1 Introduction During the past decade, term rewriting has gained an enormous importance in fields of computer science concerned with symbolic manipulation. Among others, it may be vie...