A data model proposed in 1970 by IBM's Edgar F. Codd (1923-2003) that represents data in a two-dimensional tabular format called relations. The columns (fields) of a table are called attributes, and the rows (records) are called tuples. Databases based on the relational model are called relational databases, and are widely used. Theoretically, the relational model is based on mathematical set theory, and a relational table consisting of n attributes can be thought of as the realization of a mathematical n- ary relationship. Relational algebra, which handles tables, defines set operations such as union, intersection, and difference, as well as relational operations such as join, projection, and selection. [Reference] Source: Dictionary of Library and Information Science, 4th Edition Dictionary of Library and Information Science, 5th Edition About Information |
1970年にIBM社のコッド(Edgar F. Codd 1923-2003)が提唱した,データを関係と呼ばれる二次元の表形式で表現するデータモデル.表の列(フィールド)を属性(アトリビュート),行(レコード)を組(タプル)という.関係モデルに基づくデータベースは関係データベース(またはリレーショナルデータベース)と呼ばれ,広く普及している.関係モデルは理論的には数学の集合論を基盤としており,n個の属性からなる関係表は,数学的なn項関係の実現値として捉えることができる.表を扱う関係代数として,和,積,差などの集合演算,結合,射影,選択などの関係演算が定義されている.[参照項目] 出典 図書館情報学用語辞典 第4版図書館情報学用語辞典 第5版について 情報 |
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