Concepts inIntegrating XML data sources using approximate joins
Join (SQL)
A SQL join clause combines records from two or more tables in a database. It creates a set that can be saved as a table or used as is. A is a means for combining fields from two tables by using values common to each. ANSI standard SQL specifies four types ofÂ :,,, and . As a special case, a table (base table, view, or joined table) can to itself in a self-join. A programmer writes a predicate to identify the records for joining.
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Data element
In metadata, the term data element is an atomic unit of data that has precise meaning or precise semantics.
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XML database
An XML database is a data persistence software system that allows data to be stored in XML format. This data can then be queried, exported and serialized into the desired format. XML databases are usually associated with document-oriented databases. Two major classes of XML database exist: XML-enabled: these map all XML to a traditional database (such as a relational database), accepting XML as input and rendering XML as output.
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Distance
Distance is a numerical description of how far apart objects are. In physics or everyday discussion, distance may refer to a physical length, or an estimation based on other criteria (e.g. "two counties over"). In mathematics, a distance function or metric is a generalization of the concept of physical distance.
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R-tree
R-trees are tree data structures used for spatial access methods, i.e. , for indexing multi-dimensional information such as geographical coordinates, rectangles or polygons. The R-tree was proposed by Antonin Guttman in 1984 and has found significant use in both research and real-world applications.
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Metric (mathematics)
In mathematics, a metric or distance function is a function which defines a distance between elements of a set. A set with a metric is called a metric space. A metric induces a topology on a set but not all topologies can be generated by a metric. A topological space whose topology can be described by a metric is called metrizable.
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Data
Data are values of qualitative or quantitative variables, belonging to a set of items. Data in computing are often represented by a combination of items organized in rows and multiple variables organized in columns. Data are typically the results of measurements and can be visualised using graphs or images. Data as an abstract concept can be viewed as the lowest level of abstraction from which information and then knowledge are derived. Raw data, i.e.
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Set (mathematics)
A set is a collection of well defined and distinct objects, considered as an object in its own right. Sets are one of the most fundamental concepts in mathematics. Developed at the end of the 19th century, set theory is now a ubiquitous part of mathematics, and can be used as a foundation from which nearly all of mathematics can be derived.
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