Difference constraints of the form x - y ≤ d are well studied, with efficient algorithms for satisfaction and implication, because of their connection to shortest paths. Finite domain propagation algorithms however do not make use of these algorithms, and typically treat each difference constraint as a separate propagator. Propagation does guarantee completeness of solving but can be needlessly slow. In this paper we describe how to build a (bounds consistent) global propagator for difference constraints that treats them all simultaneously. SAT modulo theory solvers have included theory solvers for difference constraints for some time. While a theory solver for difference constraints gives the basis of a global difference constraint propagator, we show how the requirements on the propagator are quite different. We give experiments showing that treating difference constraints globally can substantially improve on the standard propagation approach
{"title":"Global difference constraint propagation for finite domain solvers","authors":"Thibaut Feydy, A. Schutt, Peter James Stuckey","doi":"10.1145/1389449.1389478","DOIUrl":"https://doi.org/10.1145/1389449.1389478","url":null,"abstract":"Difference constraints of the form x - y ≤ d are well studied, with efficient algorithms for satisfaction and implication, because of their connection to shortest paths. Finite domain propagation algorithms however do not make use of these algorithms, and typically treat each difference constraint as a separate propagator. Propagation does guarantee completeness of solving but can be needlessly slow. In this paper we describe how to build a (bounds consistent) global propagator for difference constraints that treats them all simultaneously. SAT modulo theory solvers have included theory solvers for difference constraints for some time. While a theory solver for difference constraints gives the basis of a global difference constraint propagator, we show how the requirements on the propagator are quite different. We give experiments showing that treating difference constraints globally can substantially improve on the standard propagation approach","PeriodicalId":248980,"journal":{"name":"Proceedings of the 10th international ACM SIGPLAN conference on Principles and practice of declarative programming","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114006473","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Véronique Benzaken, Giuseppe Castagna, Dario Colazzo, C. Miachon
We present Pattern-by-Example (PBE), a graphical language that allows users with little or no knowledge of pattern-matching and functional programming to define complex and optimized queries on XML documents. We demonstrate the key features of PBE by commenting an interactive session and then we present its semantics by formally defining a translation from PBE graphical queries into CQL ones. The advantages of the approach are twofold. First, it generates queries that are provably correct with respect to types: the type of the result is displayed to the user and this constitutes a first and immediate visual check of the semantic correctness of the resulting query. The second advantage is that a semantics formally-thus, unambiguously-defined is an important advancement over some current approaches in which standard usage and learning methods are based on "trial and error" techniques
{"title":"Pattern by example: type-driven visual programming of XML queries","authors":"Véronique Benzaken, Giuseppe Castagna, Dario Colazzo, C. Miachon","doi":"10.1145/1389449.1389466","DOIUrl":"https://doi.org/10.1145/1389449.1389466","url":null,"abstract":"We present Pattern-by-Example (PBE), a graphical language that allows users with little or no knowledge of pattern-matching and functional programming to define complex and optimized queries on XML documents. We demonstrate the key features of PBE by commenting an interactive session and then we present its semantics by formally defining a translation from PBE graphical queries into CQL ones. The advantages of the approach are twofold. First, it generates queries that are provably correct with respect to types: the type of the result is displayed to the user and this constitutes a first and immediate visual check of the semantic correctness of the resulting query. The second advantage is that a semantics formally-thus, unambiguously-defined is an important advancement over some current approaches in which standard usage and learning methods are based on \"trial and error\" techniques","PeriodicalId":248980,"journal":{"name":"Proceedings of the 10th international ACM SIGPLAN conference on Principles and practice of declarative programming","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130755889","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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