Abstract As science communities and commercial organisations increasingly exploit XML as a means ... more Abstract As science communities and commercial organisations increasingly exploit XML as a means of exchanging and disseminating information, the selective exposure of information in XML has become an important issue. In this paper, we present a novel XML security framework developed to enforce a generic, flexible access-control mechanism for XML data management, which supports efficient and secure query access, without revealing sensitive information to unauthorized users.
Abstract Data quality is one of the most important problems in data management. A database system... more Abstract Data quality is one of the most important problems in data management. A database system typically aims to support the creation, maintenance, and use of large amount of data, focusing on the quantity of data. However, real-life data are often dirty: inconsistent, duplicated, inaccurate, incomplete, or stale. Dirty data in a database routinely generate misleading or biased analytical results and decisions, and lead to loss of revenues, credibility and customers.
Methods and apparatus are provided for detecting data inconsistencies. Methods are disclosed for ... more Methods and apparatus are provided for detecting data inconsistencies. Methods are disclosed for determining whether a set of conditional functional dependencies are consistent; determining a minimal cover of a set of conditional functional dependencies and detecting a violation of one or more conditional functional dependencies in a set of conditional functional dependencies.
Abstract. We demonstrate iMONDRIAN, a component of the MONDRIAN annotation management system. Dis... more Abstract. We demonstrate iMONDRIAN, a component of the MONDRIAN annotation management system. Distinguishing features of MONDRIAN are (i) the ability to annotate sets of values (ii) the annotation-aware query algebra. On top of that, iMONDRIAN offers an intuitive visual interface to annotate and query scientific databases.
Abstract This article investigates the question of whether a partially closed database has comple... more Abstract This article investigates the question of whether a partially closed database has complete information to answer a query. In practice an enterprise often maintains master data D m, a closed-world database. We say that a database D is partially closed if it satisfies a set V of containment constraints of the form q (D) &subse; p (D m), where q is a query in a language LC and p is a projection query. The part of D not constrained by (D m, V) is open, from which some tuples may be missing.
We show that there is a query expressible in first-order logic over the reals that returns, on an... more We show that there is a query expressible in first-order logic over the reals that returns, on any given semi-algebraic set A, for every point, a radius around which A is conical in every small enough box. We obtain this result by combining results from differential topology and real algebraic geometry, with recent algorithmic results by Rannou.
Abstract We present Semandaq, a prototype system for improving the quality of relational data. Ba... more Abstract We present Semandaq, a prototype system for improving the quality of relational data. Based on the recently proposed conditional functional dependencies (CFDs), it detects and repairs errors and inconsistencies that emerge as violations of these constraints.
Abstract We study the satisfiability problem associated with XPath in the presence of DTDs. This ... more Abstract We study the satisfiability problem associated with XPath in the presence of DTDs. This is the problem of determining, given a query p in an XPath fragment and a DTD D, whether or not there exists an XML document T such that T conforms to D and the answer of p on T is nonempty. We consider a variety of XPath fragments widely used in practice, and investigate the impact of different XPath operators on the satisfiability analysis.
Abstract We propose a class of constraints, referred to as conditional functional dependencies (C... more Abstract We propose a class of constraints, referred to as conditional functional dependencies (CFDs), and study their applications in data cleaning. In contrast to traditional functional dependencies (FDs) that were developed mainly for schema design, CFDs aim at capturing the consistency of data by incorporating bindings of semantic ally related values. For CFDs we provide an inference system analogous to Armstrong's axioms for FDs, as well as consistency analysis.
When transforming data one often wants certain information in the data source to be preserved, ie... more When transforming data one often wants certain information in the data source to be preserved, ie, we identify parts of the source data and require these parts to be transformed without loss of information. We characterize the preservation of selected information in terms of the notions of invertibility and query preservation, in a setting when transformations are specified as a view V (a set of queries), and source information is selected by a query Q.
Abstract This paper investigates three problems identified in [1] for annotation propagation, nam... more Abstract This paper investigates three problems identified in [1] for annotation propagation, namely, the view side-effect, source side-effect, and annotation placement problems. Given annotations entered for a tuple or an attribute in a view, these problems ask what tuples or attributes in the source have to be annotated to produce the view annotations. As observed in [1], these problems are fundamental not only for data provenance but also for the management of view updates.
Abstract We address a fundamental question concerning spatio-temporal database systems:“What are ... more Abstract We address a fundamental question concerning spatio-temporal database systems:“What are exactly spatio-temporal queries?” We define spatio-temporal queries to be computable mappings that are also generic, meaning that the result of a query may only depend to a limited extent on the actual internal representation of the spatio-temporal data.
Abstract Databases in real life are often neither entirely closed-world nor entirely open-world. ... more Abstract Databases in real life are often neither entirely closed-world nor entirely open-world. Indeed, databases in an enterprise are typically partially closed, in which a part of the data is constrained by master data that contains complete information about the enterprise in certain aspects [21]. It has been shown that despite missing tuples, such a database may turn out to have complete information for answering a query [9].
Abstract We consider spatial databases in the plane that can be defined by polynomial constraint ... more Abstract We consider spatial databases in the plane that can be defined by polynomial constraint formulas. Motivated by applications in geographic information systems, we investigate linear approximations of spatial databases and study in which language they can be expressed effectively.
We consider n-dimensional semi-algebraic spatial databases. We compute in first-order logic exten... more We consider n-dimensional semi-algebraic spatial databases. We compute in first-order logic extended with a transitive closure operator, a linear spatial database which characterizes the semi-algebraic spatial database up to a homeomorphism. In this way, we generalize our earlier results to semi-algebraic spatial databases in arbitrary dimensions, our earlier results being true for only two dimensions.
This paper addresses the question whether one can determine the connectivity of a semi-algebraic ... more This paper addresses the question whether one can determine the connectivity of a semi-algebraic set in three dimensions by looking only at two-dimensional “samples” of the set, where these samples are defined by first-order queries. The question is answered negatively for two classes of first-order queries: cartesian-product-free, and positive one-pass.
The formalism of constraint databases, in which possibly infinite data sets are described by Bool... more The formalism of constraint databases, in which possibly infinite data sets are described by Boolean combinations of polynomial inequality and equality constraints, has its main application area in spatial databases. The standard query language for polynomial constraint databases is first-order logic over the reals. Because of the limited expressive power of this logic with respect to queries that are important in spatial data base applications, various extensions have been introduced.
First of all, I would like to thank Jan Van den Bussche for his support during the last four year... more First of all, I would like to thank Jan Van den Bussche for his support during the last four years. His never ending enthusiasm and advice made this dissertation possible. His intensive use of red ballpoints, learned me, hopefully, how to write scientific texts. Further, I am grateful to Bart Kuijpers. His geometrical insights were of great help. I am also grateful to Peter Revesz. The Renumbering Algorithm in Chapter 6 is the result of our joint work. I am also grateful to Bart Goethals.
Abstract As science communities and commercial organisations increasingly exploit XML as a means ... more Abstract As science communities and commercial organisations increasingly exploit XML as a means of exchanging and disseminating information, the selective exposure of information in XML has become an important issue. In this paper, we present a novel XML security framework developed to enforce a generic, flexible access-control mechanism for XML data management, which supports efficient and secure query access, without revealing sensitive information to unauthorized users.
Abstract Data quality is one of the most important problems in data management. A database system... more Abstract Data quality is one of the most important problems in data management. A database system typically aims to support the creation, maintenance, and use of large amount of data, focusing on the quantity of data. However, real-life data are often dirty: inconsistent, duplicated, inaccurate, incomplete, or stale. Dirty data in a database routinely generate misleading or biased analytical results and decisions, and lead to loss of revenues, credibility and customers.
Methods and apparatus are provided for detecting data inconsistencies. Methods are disclosed for ... more Methods and apparatus are provided for detecting data inconsistencies. Methods are disclosed for determining whether a set of conditional functional dependencies are consistent; determining a minimal cover of a set of conditional functional dependencies and detecting a violation of one or more conditional functional dependencies in a set of conditional functional dependencies.
Abstract. We demonstrate iMONDRIAN, a component of the MONDRIAN annotation management system. Dis... more Abstract. We demonstrate iMONDRIAN, a component of the MONDRIAN annotation management system. Distinguishing features of MONDRIAN are (i) the ability to annotate sets of values (ii) the annotation-aware query algebra. On top of that, iMONDRIAN offers an intuitive visual interface to annotate and query scientific databases.
Abstract This article investigates the question of whether a partially closed database has comple... more Abstract This article investigates the question of whether a partially closed database has complete information to answer a query. In practice an enterprise often maintains master data D m, a closed-world database. We say that a database D is partially closed if it satisfies a set V of containment constraints of the form q (D) &subse; p (D m), where q is a query in a language LC and p is a projection query. The part of D not constrained by (D m, V) is open, from which some tuples may be missing.
We show that there is a query expressible in first-order logic over the reals that returns, on an... more We show that there is a query expressible in first-order logic over the reals that returns, on any given semi-algebraic set A, for every point, a radius around which A is conical in every small enough box. We obtain this result by combining results from differential topology and real algebraic geometry, with recent algorithmic results by Rannou.
Abstract We present Semandaq, a prototype system for improving the quality of relational data. Ba... more Abstract We present Semandaq, a prototype system for improving the quality of relational data. Based on the recently proposed conditional functional dependencies (CFDs), it detects and repairs errors and inconsistencies that emerge as violations of these constraints.
Abstract We study the satisfiability problem associated with XPath in the presence of DTDs. This ... more Abstract We study the satisfiability problem associated with XPath in the presence of DTDs. This is the problem of determining, given a query p in an XPath fragment and a DTD D, whether or not there exists an XML document T such that T conforms to D and the answer of p on T is nonempty. We consider a variety of XPath fragments widely used in practice, and investigate the impact of different XPath operators on the satisfiability analysis.
Abstract We propose a class of constraints, referred to as conditional functional dependencies (C... more Abstract We propose a class of constraints, referred to as conditional functional dependencies (CFDs), and study their applications in data cleaning. In contrast to traditional functional dependencies (FDs) that were developed mainly for schema design, CFDs aim at capturing the consistency of data by incorporating bindings of semantic ally related values. For CFDs we provide an inference system analogous to Armstrong's axioms for FDs, as well as consistency analysis.
When transforming data one often wants certain information in the data source to be preserved, ie... more When transforming data one often wants certain information in the data source to be preserved, ie, we identify parts of the source data and require these parts to be transformed without loss of information. We characterize the preservation of selected information in terms of the notions of invertibility and query preservation, in a setting when transformations are specified as a view V (a set of queries), and source information is selected by a query Q.
Abstract This paper investigates three problems identified in [1] for annotation propagation, nam... more Abstract This paper investigates three problems identified in [1] for annotation propagation, namely, the view side-effect, source side-effect, and annotation placement problems. Given annotations entered for a tuple or an attribute in a view, these problems ask what tuples or attributes in the source have to be annotated to produce the view annotations. As observed in [1], these problems are fundamental not only for data provenance but also for the management of view updates.
Abstract We address a fundamental question concerning spatio-temporal database systems:“What are ... more Abstract We address a fundamental question concerning spatio-temporal database systems:“What are exactly spatio-temporal queries?” We define spatio-temporal queries to be computable mappings that are also generic, meaning that the result of a query may only depend to a limited extent on the actual internal representation of the spatio-temporal data.
Abstract Databases in real life are often neither entirely closed-world nor entirely open-world. ... more Abstract Databases in real life are often neither entirely closed-world nor entirely open-world. Indeed, databases in an enterprise are typically partially closed, in which a part of the data is constrained by master data that contains complete information about the enterprise in certain aspects [21]. It has been shown that despite missing tuples, such a database may turn out to have complete information for answering a query [9].
Abstract We consider spatial databases in the plane that can be defined by polynomial constraint ... more Abstract We consider spatial databases in the plane that can be defined by polynomial constraint formulas. Motivated by applications in geographic information systems, we investigate linear approximations of spatial databases and study in which language they can be expressed effectively.
We consider n-dimensional semi-algebraic spatial databases. We compute in first-order logic exten... more We consider n-dimensional semi-algebraic spatial databases. We compute in first-order logic extended with a transitive closure operator, a linear spatial database which characterizes the semi-algebraic spatial database up to a homeomorphism. In this way, we generalize our earlier results to semi-algebraic spatial databases in arbitrary dimensions, our earlier results being true for only two dimensions.
This paper addresses the question whether one can determine the connectivity of a semi-algebraic ... more This paper addresses the question whether one can determine the connectivity of a semi-algebraic set in three dimensions by looking only at two-dimensional “samples” of the set, where these samples are defined by first-order queries. The question is answered negatively for two classes of first-order queries: cartesian-product-free, and positive one-pass.
The formalism of constraint databases, in which possibly infinite data sets are described by Bool... more The formalism of constraint databases, in which possibly infinite data sets are described by Boolean combinations of polynomial inequality and equality constraints, has its main application area in spatial databases. The standard query language for polynomial constraint databases is first-order logic over the reals. Because of the limited expressive power of this logic with respect to queries that are important in spatial data base applications, various extensions have been introduced.
First of all, I would like to thank Jan Van den Bussche for his support during the last four year... more First of all, I would like to thank Jan Van den Bussche for his support during the last four years. His never ending enthusiasm and advice made this dissertation possible. His intensive use of red ballpoints, learned me, hopefully, how to write scientific texts. Further, I am grateful to Bart Kuijpers. His geometrical insights were of great help. I am also grateful to Peter Revesz. The Renumbering Algorithm in Chapter 6 is the result of our joint work. I am also grateful to Bart Goethals.
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