Journal ArticleDOI
Imprecision and incompleteness in relational databases: survey
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The article surveys and compares the basic approaches that address issues of imprecision and incompleteness in relational databases.Abstract:
Most database systems are designed under assumptions of precision and completeness of both the data they store and the requests to retrieve data, even though in reality these assumptions are often false. In recent years, considerable attention has been given to issues of imprecision and incompleteness in databases. The article surveys and compares the basic approaches that address these issues in relational databases.read more
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Journal ArticleDOI
Supporting valid-time indeterminacy
TL;DR: This paper extends the SQL data model and query language to support valid-time indeterminacy, and represents the occurrence time of an event with a set of possible instants, delimiting when the event might have occurred, and a probability distribution over that set.
Ontology-based Information Retrieval
TL;DR: This thesis presents methods for introducing ontologies in information retrieval, and appears that the fuzzy set model comprises the flexibility needed when generalizing to an ontology-based retrieval model and, with the introduction of a hierarchical fuzzy aggregation principle, compound concepts can be handled in a straightforward and natural manner.
Proceedings ArticleDOI
Imprecise and uncertain information in databases: an evidential approach
TL;DR: A novel approach for representing imprecise and uncertain data and evaluating queries in the framework of an extended relational database model based on the Dempster-Shafer theory of evidence is proposed.
Proceedings ArticleDOI
Valid-time indeterminacy
TL;DR: In valid-time indeterminacy, it is known that an event stored in a temporal database did in fact occur, but it is not known exactly when the event occurred.
Book ChapterDOI
A Bibliography on Uncertainty Management in Information Systems
TL;DR: This is an evolving bibliography of documents on uncertainty and imprecision in information systems, focusing almost exclusively on database and knowledge-base systems, with few references on other kinds of information systems.
References
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Journal ArticleDOI
A relational model of data for large shared data banks
TL;DR: In this article, a model based on n-ary relations, a normal form for data base relations, and the concept of a universal data sublanguage are introduced, and certain operations on relations are discussed and applied to the problems of redundancy and consistency in the user's model.
Journal Article
A relational model of data for large shared data banks. 1970
TL;DR: A model based on n-ary relations, a normal form for data base relations, and the concept of a universal data sublanguage are introduced and certain operations on relations are discussed and applied to the problems of redundancy and consistency in the user's model.
Book
Theory of Relational Databases
TL;DR: The method of operating a water-cooled neutronic reactor having a graphite moderator which comprises flowing a gaseous mixture of carbon dioxide and helium, in which the helium comprises 40-60 volume percent of the mixture, in contact with thegraphite moderator.
Journal ArticleDOI
Extending the database relational model to capture more meaning
TL;DR: In this paper, the relational model is extended to support atomic and molecular semantics, which is a synthesis of many ideas from the published work in semantic modeling plus the introduction of new rules for insertion, update, and deletion.
Book
The theory of relational databases
TL;DR: In this article, the graphite moderator is replaced by a gaseous mixture of carbon dioxide and helium, in which the helium comprises 40-60 volume percent of the mixture.