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| In [[descriptive complexity]], a '''query''' is a mapping from structures of one [[signature (logic)|signature]] to structures of another vocabulary. [[Neil Immerman]], in his book "Descriptive Complexity", "use[s] the concept of query as the fundamental paradigm of computation" (p. 17).
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| Given signatures <math>\sigma</math> and <math>\tau</math>, we define the set of [[structure (mathematical logic)|structure]]s on each language, <math>\mbox{STRUC}[\sigma]</math> and <math>\mbox{STRUC}[\tau]</math>. A query is then any mapping
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| <blockquote>
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| <math>I : \mbox{STRUC}[\sigma] \to \mbox{STRUC}[\tau]</math>
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| </blockquote>
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| [[Computational complexity theory]] can then be phrased in terms of the power of the mathematical logic necessary to express a given query.
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| ==Order-independent queries==
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| A query is '''order-independent''' if the ordering of objects in the structure does not affect the results of the query. In databases, these queries correspond to [[generic query|generic queries]] (Immerman 1999, p. 18).<!-- This isn't a great reference for this information, since it's in the "background" section. A reference that goes into more detail would be great. --> A query is order-independent iff <math> I(\mathfrak{A}) \equiv I(\mathfrak{B})</math> for any isomorphic structures <math>\mathfrak{A}</math> and <math>\mathfrak{B}</math>.
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| ==References==
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| *{{cite book | last = Immerman | first = Neil | authorlink = Neil Immerman | title = Descriptive Complexity | year = 1999 | publisher = Springer-Verlag | location = New York | isbn = 0-387-98600-6}}
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| {{comp-sci-theory-stub}}
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| [[Category:Descriptive complexity]]
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Latest revision as of 02:18, 10 December 2014
The author is known as Araceli Gulledge. Interviewing is what I do for a residing but I strategy on changing it. To maintain birds is one of the things he enjoys most. For many years she's been living in Kansas.
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