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The DEDALE System for Complex Spatial Queries
, 1998
"... This paper presents dedale, a spatial database system intended to overcome some limitations of current systems by providing an abstract and nonspecialized data model and query language for the representation and manipulation of spatial objects. dedale relies on a logical model based on linear const ..."
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Cited by 94 (9 self)
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This paper presents dedale, a spatial database system intended to overcome some limitations of current systems by providing an abstract and nonspecialized data model and query language for the representation and manipulation of spatial objects. dedale relies on a logical model based on linear constraints, which generalizes the constraint database model of [KKR90]. While in the classical constraint model, spatial data is always decomposed into its convex components, in dedale holes are allowed to fit the need of practical applications. The logical representation of spatial data although slightly more costly in memory, has the advantage of simplifying the algorithms. dedale relies on nested relations, in which all sorts of data (thematic, spatial, etc.) are stored in a uniform fashion. This new data model supports declarative query languages, which allow an intuitive and efficient manipulation of spatial objects. Their formal foundation constitutes a basis for practical query optimizati...
Efficient Computation of Spatial Joins
, 1993
"... Spatial joins are join operations that involve spatial data types and operators. Due to some basic properties of spatial data, many conventional join processing strategies suffer serious performance penalties or are not applicable at all in this case. In this paper we explore which of the join strat ..."
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Cited by 94 (4 self)
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Spatial joins are join operations that involve spatial data types and operators. Due to some basic properties of spatial data, many conventional join processing strategies suffer serious performance penalties or are not applicable at all in this case. In this paper we explore which of the join strategies known from conventional databases can be applied to spatial joins as well, and how some of these techniques can be modified to be more efficient in the context of spatial data. Furthermore, we describe a class of tree structures, called generalization trees, that can be applied efficiently to compute spatial joins in a hierarchical manner. Finally, we model the performance of the most promising strategies analytically and conduct a comparative study. Parts of this work have been carried out while the author was visiting the International Computer Science Institute and the University of California at Berkeley. 1 1 Introduction Spatial databases have become a very active research top...
Queries and query processing in objectoriented database systems
 ACM TRANSACTIONS ON INFORMATION SYSTEMS
, 1990
"... One of the basic functionalities of database management systems (DBMSs) is to be able to process declarative user queries. The first generation of objectoriented DBMSs did not provide declarative query capabilities. However, the last decade has seen significant research in defining query models (in ..."
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Cited by 80 (8 self)
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One of the basic functionalities of database management systems (DBMSs) is to be able to process declarative user queries. The first generation of objectoriented DBMSs did not provide declarative query capabilities. However, the last decade has seen significant research in defining query models (including calculi, algebra and user languages) and in techniques for processing and optimizing them. Many of the current commercial systems provide at least rudimentary query capabilities. In this chapter we discuss the techniques that have been developed for processing objectoriented queries. Our particular emphasis is on extensible query processing architectures and techniques. The other chapters in this book on query languages and optimization techniques complement this chapter.
SimilarityBased Queries
, 1995
"... We develop a domainindependent framework for defining queries in terms of similarity of objects. Our framework has three components: a pattern language, a transformation rule language, and a query language. The pattern language specifies classes of objects, the transformation rule language defines ..."
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Cited by 74 (8 self)
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We develop a domainindependent framework for defining queries in terms of similarity of objects. Our framework has three components: a pattern language, a transformation rule language, and a query language. The pattern language specifies classes of objects, the transformation rule language defines similarity by specifying the similaritypreserving transformations, and the whole package is wrapped in a general query language. The framework can be "tuned" to the needs of a specific application domain, such as time sequences, molecules, text strings or images, by the choice of these languages. We demonstrate the framework by presenting a specific instance on a specific domain  the domain of sequences. We start with sequences over a finite alphabet, and then consider sequences over infinite ordered domains. The basic pattern language we use is regular expressions, and the query language is calculusbased. We show that even when the pattern/query languages chosen are not too powerful, t...
Monotonic Aggregation in Deductive Databases
 Journal of Computer and System Sciences
, 1992
"... We propose a semantics for aggregates in deductive databases based on a notion of minimality. Unlike some previous approaches, we form a minimal model of a program component including aggregate operators, rather than insisting that the aggregate apply to atoms that have been fully determined, or tha ..."
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Cited by 67 (3 self)
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We propose a semantics for aggregates in deductive databases based on a notion of minimality. Unlike some previous approaches, we form a minimal model of a program component including aggregate operators, rather than insisting that the aggregate apply to atoms that have been fully determined, or that aggregate functions are rewritten in terms of negation. In order to guarantee the existence of such a minimal model we need to insist that the domains over which we are aggregating are complete lattices, and that the program is in a sense monotonic. Our approach generalizes previous approaches based on the wellfounded semantics and various forms of stratification. We are also able to handle a large variety of monotonic (or pseudomonotonic) aggregate functions. 1 Introduction Deductive databases allow views to be defined using programs consisting of logical rules. Recently, a number of researchers have considered adding aggregation to the rule language. If the aggregation is applied in a...
Towards Tractable Algebras for Bags
, 1993
"... Bags, i.e. sets with duplicates, are often used to implement relations in database systems. In this paper, we study the expressive power of algebras for manipulating bags. The algebra we present is a simple extension of the nested relation algebra. Our aim is to investigate how the use of bags in ..."
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Cited by 62 (5 self)
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Bags, i.e. sets with duplicates, are often used to implement relations in database systems. In this paper, we study the expressive power of algebras for manipulating bags. The algebra we present is a simple extension of the nested relation algebra. Our aim is to investigate how the use of bags in the language extends its expressive power, and increases its complexity. We consider two main issues, namely (i) the impact of the depth of bag nesting on the expressive power, and (ii) the complexity and the expressive power induced by the algebraic operations. We show that the bag algebra is more expressive than the nested relation algebra (at all levels of nesting), and that the difference may be subtle. We establish a hierarchy based on the structure of algebra expressions. This hierarchy is shown to be highly related to the properties of the powerset operator. Invited to a special issue of the Journal of Computer and System Sciences selected from ACM Princ. of Database Systems,...
MultiRelational Data Mining: An Introduction
"... Data mining algorithms look for patterns in data. While most existing data mining approaches look for patterns in a single data table, multirelational data mining (MRDM) approaches look for patterns that involve multiple tables ..."
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Cited by 61 (0 self)
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Data mining algorithms look for patterns in data. While most existing data mining approaches look for patterns in a single data table, multirelational data mining (MRDM) approaches look for patterns that involve multiple tables
On Verifying Consistency of XML Specifications
"... XML specifications often consist of a type definition (typically, a DTD) and a set of integrity constraints. It has been shown previously that such specifications can be inconsistent, and thus it is often desirable to check consistency at compiletime. It is known that for general keys and foreign k ..."
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Cited by 53 (10 self)
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XML specifications often consist of a type definition (typically, a DTD) and a set of integrity constraints. It has been shown previously that such specifications can be inconsistent, and thus it is often desirable to check consistency at compiletime. It is known that for general keys and foreign keys, and DTDs, the consistency problem is undecidable; however, it becomes NPcomplete when all keys are oneattribute (unary), and tractable, if no foreign keys are used.
Evaluation of Relational Algebras Incorporating the Time Dimension in Databases
 ACM Computing Surveys
, 1991
"... The relational algebra is a procedural query language for relational databases. In this paper we survey extensions of the relational algebra that can query databases recording timevarying data. Such an algebra is a critical part of a temporal DBMS. We identify 26 criteria that provide an objective ..."
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Cited by 53 (9 self)
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The relational algebra is a procedural query language for relational databases. In this paper we survey extensions of the relational algebra that can query databases recording timevarying data. Such an algebra is a critical part of a temporal DBMS. We identify 26 criteria that provide an objective basis for evaluating temporal algebras, Seven of the criteria are shown to be mutually unsatisfiable, implying there can be no perfect temporal algebra, Choices made as to which of the incompatible criteria are satisfied characterize existing algebras Twelve timeoriented algebras are summarized and then evaluated against the criteria. We demonstrate that the design space has in some sense been explored in that all combinations of basic design decisions have at least one representative algebra. Coverage of the remaining criteria provides one measure of the quality of each algebra We argue that all of the criteria are independent and that the criteria identified as compatible are indeed so, Finally, we list plausible properties proposed by others that are either subsumed by other criteria, are not well defined, or have no objective basis for being evaluated. The algebras realize many different approaches to what appears initially to be a straightforward design task.