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From Datalog rules to efficient programs with time and space guarantees
 In PPDP ’03: Proceedings of the 5th ACM SIGPLAN International Conference on Principles and Practice of Declarative Programming
, 2003
"... This paper describes a method for transforming any given set of Datalog rules into an efficient specialized implementation with guaranteed worstcase time and space complexities, and for computing the complexities from the rules. The running time is optimal in the sense that only useful combinations ..."
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Cited by 33 (12 self)
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This paper describes a method for transforming any given set of Datalog rules into an efficient specialized implementation with guaranteed worstcase time and space complexities, and for computing the complexities from the rules. The running time is optimal in the sense that only useful combinations of facts that lead to all hypotheses of a rule being simultaneously true are considered, and each such combination is considered exactly once. The associated space usage is optimal in that it is the minimum space needed for such consideration modulo scheduling optimizations that may eliminate some summands in the space usage formula. The transformation is based on a general method for algorithm design that exploits fixedpoint computation, incremental maintenance of invariants, and combinations of indexed and linked data structures. We apply the method to a number of analysis problems, some with improved algorithm complexities and all with greatly improved algorithm understanding and greatly simplified complexity analysis.
Parametric regular path queries
 In PLDI ’04: Proceedings of the ACM SIGPLAN 2004 conference on Programming Language Design and Implementation
, 2004
"... Regular path queries are a way of declaratively expressing queries on graphs as regularexpressionlike patterns that are matched against paths in the graph. There are two kinds of queries: existential queries, which specify properties about individual paths, and universal queries, which specify pro ..."
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Cited by 28 (4 self)
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Regular path queries are a way of declaratively expressing queries on graphs as regularexpressionlike patterns that are matched against paths in the graph. There are two kinds of queries: existential queries, which specify properties about individual paths, and universal queries, which specify properties about all paths. They provide a simple and convenient framework for expressing program analyses as queries on graph representations of programs, for expressing verification (modelchecking) problems as queries on transition systems, for querying semistructured data, etc. Parametric regular path queries extend the patterns with variables, called parameters, which significantly increase the expressiveness by allowing additional information along single or multiple paths to be captured and related. This paper shows how a variety of program analysis and modelchecking problems can be expressed easily and succinctly using parametric regular path queries. The paper describes the specification, design, analysis, and implementation of algorithms and data structures for efficiently solving existential and universal parametric regular path queries. Major contributions include the first complete algorithms and data structures for directly and efficiently solving existential and universal parametric regular path queries, detailed complexity analysis of the algorithms, detailed analytical and experimental performance comparison of variations of the algorithms and data structures, and investigation of efficiency tradeoffs between different formulations of queries. Categories and Subject Descriptors D.2.4 [Software Engineering]: Software/Program verification—model
Transforming the .NET Intermediate Language Using Path Logic Programming
, 2002
"... Path logic programming is a modest extension of Prolog for the specification of program transformations. We give an informal introduction to this extension, and we show how it can be used in coding standard compiler optimisations, and also a number of obfuscating transformations. The object language ..."
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Cited by 21 (5 self)
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Path logic programming is a modest extension of Prolog for the specification of program transformations. We give an informal introduction to this extension, and we show how it can be used in coding standard compiler optimisations, and also a number of obfuscating transformations. The object language is the Microsoft .NET intermediate language (IL).
Querying Complex Graphs
 Proceedings of the Eighth Intl Symposium on Practical Aspects of Declarative Languages (PADL
, 2006
"... Abstract. This paper presents a powerful language for querying complex graphs and a method for generating efficient implementations that can answer queries with complexity guarantees. The graphs may have edge labels that may have parameters, and easily and naturally capture complex interrelated obje ..."
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Cited by 11 (2 self)
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Abstract. This paper presents a powerful language for querying complex graphs and a method for generating efficient implementations that can answer queries with complexity guarantees. The graphs may have edge labels that may have parameters, and easily and naturally capture complex interrelated objects in objectoriented systems and XML data. The language is built on extended regular path expressions with variables and scoping, and can express queries more easily and clearly than previous query languages. The method for implementation first transforms queries into Datalog with limited extensions. It then extends a previous method to generate specialized algorithms and complexity formulas from Datalog with these extensions. 1
From Datalog Rules to Optimal Algorithms with Time and Space Guarantees
, 2003
"... This paper describes a method for transforming any given set of Datalog rules into an ecient implementation with guaranteed worstcase time and space complexities, and for computing the complexities from the rules. The running time is optimal in the sense that only useful combinations of facts that ..."
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This paper describes a method for transforming any given set of Datalog rules into an ecient implementation with guaranteed worstcase time and space complexities, and for computing the complexities from the rules. The running time is optimal in the sense that only useful combinations of facts that lead to all hypotheses of a rule being simultaneously true are considered, and each such combination is considered exactly once. The associated space usage is optimal in that it is the minimum space needed for such consideration modulo scheduling optimizations that may eliminate some summands in the space usage formula. The transformation is based on a general method for algorithm design that exploits fixedpoint computation, incremental maintenance of invariants, and combinations of indexed and linked data structures. We apply the method to a number of analysis problems, some with improved algorithm complexities and all with greatly improved algorithm understanding and greatly simplified complexity analysis.
AThe Complexity of Regular Expressions and Property Paths in
"... The World Wide Web Consortium (W3C) recently introduced property paths in SPARQL 1.1, a query language for RDF data. Property paths allow SPARQL queries to evaluate regular expressions over graphstructured data. However, they differ from standard regular expressions in several notable aspects. For ..."
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The World Wide Web Consortium (W3C) recently introduced property paths in SPARQL 1.1, a query language for RDF data. Property paths allow SPARQL queries to evaluate regular expressions over graphstructured data. However, they differ from standard regular expressions in several notable aspects. For example, they have a limited form of negation, they have numerical occurrence indicators as syntactic sugar, and their semantics on graphs is defined in a nonstandard manner. We formalize the W3C semantics of property paths and investigate various query evaluation problems on graphs. More specifically, let x and y be two nodes in an edgelabeled graph and r be an expression. We study the complexities of (1) deciding whether there exists a path from x to y that matches r and (2) counting how many paths from x to y match r. Our main results show that, compared to an alternative semantics of regular expressions on graphs, the complexity of (1) and (2) under W3C semantics is significantly higher. Whereas the alternative semantics remains in polynomial time for large fragments of expressions, the W3C semantics makes problems (1) and (2) intractable almost immediately. As a sideresult, we prove that the membership problem for regular expressions with numerical occurrence indicators and negation is in polynomial time.