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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Equality-generating dependency ： ウィキペディア英語版 Equality-generating dependency In relational database theory, an equality-generating dependency (EGD) is a certain kind of constraint on data. It is a subclass of the class of embedded dependencies (ED). An ED is a sentence in first-order logic of the form: ∀x1 ... xn, P(x1, ..., xn) → ∃z1, ..., zk, Q(y1, ..., ym) where = \ , and P is a possibly empty and Q is a non-empty conjunction of equality atoms. A n equality atom has the form wi = wj where each of the w, ..., wh, wi, wj, are variables or constants. An algorithm known as the chase takes as input an instance that may or may not satisfy a set of EGDs (or more generally a set of EDs), and, if it terminates (which is a priori undecidable), output an instance that does satisfy the EGDs. == References == 〔 * Serge Abiteboul, Richard B. Hull, Victor Vianu: Foundations of Databases. Addison-Wesley, 1995. * Alin Deutsch, FOL Modeling of Integrity Constraints, http://db.ucsd.edu/pubsFileFolder/305.pdf 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Equality-generating dependency」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.