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Efficient algorithms for processing XPath queries
TLDR
Our experimental analysis of several popular XPath processors reveals a striking fact: Query evaluation in each of the systems requires time exponential in the size of queries in the worst case. Expand
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Efficient Algorithms for Processing XPath Queries
TLDR
We present the first XPath query evaluation algorithm that runs in polynomial time with respect to the size of both the data and of the query. Expand
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The complexity of XPath query evaluation
TLDR
We show that both the data complexity and query complexity of XPath 1.0 fall into lower (highly parallelizable) complexity classes, but that the combined complexity is PTIME-hard. Expand
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Static analysis and optimization of semantic web queries
TLDR
We propose a tree representation for SPARQL queries, called pattern trees, which captures the class of well-designed graph patterns and which can be considered as a query execution plan. Expand
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Tractable Counting of the Answers to Conjunctive Queries
TLDR
A systematic search for tractable fragments of the counting problem of CQs, i.e., the problem of counting the answers to a CQ. Expand
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Bounded treewidth as a key to tractability of knowledge representation and reasoning
TLDR
We show that virtually all relevant decision problems in the area of abduction, closed world reasoning, circumscription, and disjunctive logic programming become tractable if the treewidth of the graphs is bounded by a fixed constant. Expand
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Capturing Relational Schemas and Functional Dependencies in RDFS
TLDR
We introduce expressive identification constraints to capture functional dependencies and define an RDF Normal Form, which precisely captures the classical Boyce-Codd Normal Form of relational schemas. Expand
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The complexity of evaluating tuple generating dependencies
TLDR
We study the query complexity and combined complexity of tuple generating dependencies (tgds) which enforce the presence of certain tuples in a database instance if certain other tuples are already present. Expand
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Counting Complexity of Propositional Abduction
TLDR
We concentrate on propositional abduction, where the background knowledge is given by a propositional formula. Expand
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Monadic datalog over finite structures with bounded treewidth
TLDR
We propose monadic datalog (i.e., data log where all intentional predicate symbols are unary) as an alternative method to tackle this class of fixed-parameter tractable problems. Expand
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