Model Networks - Model Networks Outline Introduction Basic...

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Model Networks
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Outline Introduction Basic Concepts Data-Structure Diagrams General Relationships Mapping of Networks to Files Modified Ring Structures Two Data-Structure Diagrams The OSL Model Seven layers of the OSI model
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Model Networks The network model's original inventor was Charles Bachman. Developed into a standard specification published in 1969 by the CODASY Consortium. Database model conceived as a flexible way of representing objects and their relationships. Distinguishing feature is that the schema, viewed as a graph in which object types are nodes and relationship types are arcs, is not restricted to being a hierarchy.
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Basic Concepts Data are represented by collections of records . similar to an entity in the E-R model Records and their fields are represented as record type type customer = record type account = record customer-name: string; account-number: integer; customer-street: string; balance: integer; customer-city: string; end end Relationships among data are represented by links similar to a restricted (binary) form of an E-R relationship restrictions on links depend on whether the relationship is many- many, many-to-one, or one-to-one.
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Data-Structure Diagrams Schema representing the design of a network database. A data-structure diagram consists of two basic components:
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Model Networks - Model Networks Outline Introduction Basic...

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