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Conceptual Modeling Foundations for a Web of Knowledge
"... The semantic web purports to be a web of knowledge that can answer our questions, help us reason about everyday problems as well as scientific endeavors, and service many of our wants and needs. Researchers and others expound various views about exactly what this means. Here we propose an answer w ..."
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Cited by 11 (9 self)
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The semantic web purports to be a web of knowledge that can answer our questions, help us reason about everyday problems as well as scientific endeavors, and service many of our wants and needs. Researchers and others expound various views about exactly what this means. Here we propose an answer with conceptual modeling as its foundation. We define a web of knowledge as a collection of interconnected knowledge bundles superimposed over a web of documents. Knowledge bundles are conceptual model instances augmented with facilities that provide for both extensional and intensional facts, for linking between knowledge bundles yielding a web of data, and for linking to an underlying document collection providing a means of authentication. We formally define both the component parts of these augmented conceptual models and their synergistic interconnections. As for practicalities, we discuss problems regarding the potentially high cost of constructing a web of knowledge and explain how they may be mitigated. We also discuss usage issues and show how untrained users can interact with and gain benefit from
Queries with Guarded Negation
, 2012
"... A wellestablished and fundamental insight in database theory is that negation (also known as complementation) tends to make queries difficult to process and difficult to reason about. Many basic problems are decidable and admit practical algorithms in the case of unions of conjunctive queries, but ..."
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Cited by 9 (2 self)
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A wellestablished and fundamental insight in database theory is that negation (also known as complementation) tends to make queries difficult to process and difficult to reason about. Many basic problems are decidable and admit practical algorithms in the case of unions of conjunctive queries, but become difficult or even undecidable when queries are allowed to contain negation. Inspired by recent results in finite model theory, we consider a restricted form of negation, guarded negation. We introduce a fragment of SQL, called GNSQL, as well as a fragment of Datalog with stratified negation, called GNDatalog, that allow only guarded negation, and we show that these query languages are computationally well behaved, in terms of testing query containment, query evaluation, openworld query answering, and boundedness. GNSQL and GNDatalog subsume a number of well known query languages and constraint languages, such as unions of conjunctive queries, monadic Datalog, and frontierguarded tgds. In addition, an analysis of standard benchmark workloads shows that many uses of negation in SQL in practice are guarded.
E.: Probabilistic Datalog+/ under the Distribution
 Semantics, International Workshop on Description Logics
"... Abstract. We apply the distribution semantics for probabilistic ontologies (named DISPONTE) to the Datalog+/ language. In DISPONTE the formulas of a probabilistic ontology can be annotated with an epistemic or a statistical probability. The epistemic probability represents a degree of confidence in ..."
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Cited by 6 (4 self)
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Abstract. We apply the distribution semantics for probabilistic ontologies (named DISPONTE) to the Datalog+/ language. In DISPONTE the formulas of a probabilistic ontology can be annotated with an epistemic or a statistical probability. The epistemic probability represents a degree of confidence in the formula, while the statistical probability considers the populations to which the formula is applied. The probability of a query is defined in terms of finite set of finite explanations for the query, where an explanation is a set of possibly instantiated formulas that is sufficient for entailing the query. The probability of a query is computed from the set of explanations by making them mutually exclusive. We also compare the DISPONTE approach for Datalog+/ ontologies with that of Probabilistic Datalog+/, where an ontology is composed of a Datalog+/ theory whose formulas are associated to an assignment of values for the random variables of a companion Markov Logic Network. 1
Probabilistic Ontologies in Datalog+/
"... Abstract. In logic programming the distribution semantics is one of the most popular approaches for dealing with uncertain information. In this paper we apply the distribution semantics to the Datalog+/ language that is grounded in logic programming and allows tractable ontology querying. In the re ..."
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Cited by 2 (2 self)
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Abstract. In logic programming the distribution semantics is one of the most popular approaches for dealing with uncertain information. In this paper we apply the distribution semantics to the Datalog+/ language that is grounded in logic programming and allows tractable ontology querying. In the resulting semantics, called DISPONTE, formulas of a probabilistic ontology can be annotated with an epistemic or a statistical probability. The epistemic probability represents a degree of confidence in the formula, while the statistical probability considers the populations to which the formula is applied. The probability of a query is defined in terms of finite set of finite explanations for the query. We also compare the DISPONTE approach for Datalog+/ ontologies with that of Probabilistic Datalog+/ where an ontology is composed of a Datalog+/theory whose formulas are associated to an assignment of values for the random variables of a companion Markov Logic Network. 1
Queries with Guarded Negation (full version)∗
"... A wellestablished and fundamental insight in database theory is that negation (also known as complementation) tends to make queries difficult to process and difficult to reason about. Many basic problems are decidable and admit practical algorithms in the case of unions of conjunctive queries, bu ..."
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Cited by 1 (0 self)
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A wellestablished and fundamental insight in database theory is that negation (also known as complementation) tends to make queries difficult to process and difficult to reason about. Many basic problems are decidable and admit practical algorithms in the case of unions of conjunctive queries, but become difficult or even undecidable when queries are allowed to contain negation. Inspired by recent results in finite model theory, we consider a restricted form of negation, guarded negation. We introduce a fragment of SQL, called GNSQL, as well as a fragment of Datalog with stratified negation, called GNDatalog, that allow only guarded negation, and we show that these query languages are computationally well behaved, in terms of testing query containment, query evaluation, openworld query answering, and boundedness. GNSQL and GNDatalog subsume a number of well known query languages and constraint languages, such as unions of conjunctive queries, monadic Datalog, and frontierguarded tgds. In addition, an analysis of standard benchmark workloads shows that most usage of negation in SQL in practice is guarded negation. 1.