Topic 2

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چکیده

The first data model was developed by Rockwell and IBM in the 1970s. It is known as the hierarchical model. The hierarchical database is a collection of records that is logically organized to conform to the upside-down tree (hierarchical) structure. Within the hierarchy, the top layer (the root) is perceived as the parent of the segment directly beneath it. While this model represents 1:M relationships well, it does not represent M:N relationships.

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تاریخ انتشار 2009