Overview
Any given database consists of relation variables (rekvars for short)
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The value of any given relvar at any given time is a relation value (relation for short)
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Every relvar represents a certain predicate
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Within any given relvar, every tuple represents a certain proposition.
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In accordance with the the Closed World Assumption, relvar R at time T contains all and only those tuples that represent instantiations of the predicate corresponding to relvar R that evaluate to TRUE at time T.
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…relations have two parts, a heading and a body. Basically the heading is a set of attributes, and the body is a set of tuple that conform to that heading.
Both RELVARs and RELATIONs have headings.
The heading of a RELVAR represents a predicate which in the intended meaning.
…a predicate isn’t really a statement as such, rather, it’s the assetion made by that statement.
Propositions can be true or false.