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Data structure diagram (DSD) is a diagram of the conceptual data model which documents the entities and their relationships, as well as the constraints that connect to them. The basic graphic notation elements of DSDs are boxes which represent entities.The arrow symbol represents relationships. Data structure diagrams are most useful for documenting complex data entities. ==Overview== Data Structure Diagram is a diagram type that is used to depict the structure of data elements in the data dictionary. The data structure diagram is a graphical alternative to the composition specifications within such data dictionary entries.〔(Data Integration Glossary ), U.S. Department of Transportation, August 2001.〕 The data structure diagrams is a predecessor of the entity-relationship model (E-R model). In DSDs, attributes are specified inside the entity boxes rather than outside of them, while relationships are drawn as boxes composed of attributes which specify the constraints that bind entities together. DSDs differ from the E-R model in that the E-R model focuses on the relationships between different entities, whereas DSDs focus on the relationships of the elements within an entity. There are several styles for representing data structure diagrams, with the notable difference in the manner of defining cardinality. The choices are between arrow heads, inverted arrow heads (crow's feet), or numerical representation of the cardinality. 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「Data structure diagram」の詳細全文を読む スポンサード リンク
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