A subschema capable of representing bi-directional 1:N "sets" (relationships) and the data management language are two of the key components that make this database model unique. The schema used for this model is conceptual organization of the entire database as the database administrator intends. The subschema defines the database portion as seen by the application programs that produce the information from the raw data that is contained in the given database. The network database model uses a data management language that defines data characteristics and the data structure in order to manipulate the data. The database management language uses a schema and subschema data definition language. The schema data definition language enables database administrators to define schema components. The subschema data definition language allows the application programs to define database components that will be used. There are a few advantages and disadvantages of using the network database model. Some advantages include conceptual simplicity, data access flexibility, conformance to standards, handle more relationship types, promote database integrity, and allows for data independence. The disadvantages of the network database model are the structure is difficult to change, this type of system is very complex, and there is a lack of structural independence. In summary the network database model is similar but different then the hierarchal database model. The network database model should be used when it is necessary to have a flexible way of representing objects and their relationships.

Additional Information...

The Network Database Model was invented by Charles Bachman in 1969 to enhance the existing hierarchical database model. He created this model to increase the flexibility and make it less difficult to understand. To make this change Bachman developed the Network Database Model to allow multiple records to be linked to the same owner file creating a many-to-many relationship rather than a one-to-many. These many-to-many relationships were formed because one owner can linked to many member files and vice versa. To make the process faster Bachman also created these relationships to provide a relation between records using direct pointers, which is the fastest method of traversing (travel across) a network database.

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