Many to many relationship is network structure - Database

Discussion

• Nirja Shah   -Posted on 30 Oct 15
  - The popularity of the network data model coincided with the popularity of the hierarchical data model.
  
  - Some data were more naturally modeled with more than one parent per child.
  
  - The network model permitted the modeling of many-to-many relationships in data.
  
  - In the year 1971, the Conference on Data Systems Languages (CODASYL) formally defined the network model.
  
  - The set construct is the basic data modeling construct in the network model.
  
  - An owner record type, a set name, and a member record type together creates a set.
  
  - The multiparent concept is supported by a member record type can have that role in more than one set.
  
  - An owner record type can also be a member or owner in another set.
  
  - The data model is a simple network, and link and intersection record types (called junction records by IDMS) may exist, as well as sets between them .
  
  - Thus, the complete network of relationships is represented by several pairwise sets; in each set some (one) record type is owner (at the tail of the network arrow) and one or more record types are members (at the head of the relationship arrow).
  
  - A set defines a 1:M relationship, although 1:1 is permitted.
  
  - The CODASYL network model is based on mathematical set theory.

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