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Reference.org
Tuple-generating dependency
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<p>In relational <a href="/facts/Database_theory/unyQa3cK">database theory</a>, a tuple-generating dependency (TGD) is a certain kind of constraint on a <a href="/facts/Relational_database/pEKGmJLy">relational database</a>. It is a subclass of the class of <a href="/facts/Embedded_dependency/rC8nWfXW">embedded dependencies</a> (EDs). </p><p>An algorithm known as <a href="/facts/Chase_(algorithm)/JfTgn5nt">the chase</a> takes as input an instance that may or may not satisfy a set of TGDs (or more generally EDs) and, if it terminates (which is a priori undecidable), outputs an instance that does satisfy the TGDs. </p>