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The logical data structure of a DBMS, whether hierarchical, network, or relational, cannot totally satisfy the requirements for a conceptual definition of data because it is limited in scope and biased toward the implementation strategy employed by the DBMS. That is unless the semantic data model is implemented in the database on purpose, a choice which may slightly impact performance but generally vastly improves productivity.
[[File:A2 4 Semantic Data Models.jpg|thumb|320px|Semantic data models.<ref name="FIPS184"/>]]
Therefore, the need to define data from a conceptual view has led to the development of [[semantic data model]]ing techniques. That is, techniques to define the meaning of data within the context of its interrelationships with other data. As illustrated in the figure the real world, in terms of resources, ideas, events, etc.,
The purpose of semantic data modeling is to create a structural model of a piece of the real world, called "universe of discourse". For this, three fundamental structural relations are considered:
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