Basic Concepts of Hierarchical and Network Data Model.

 


Basic Concepts of Hierarchical and Network Data Model


Network data model


In the network data model, data model data are represented by collections of records. Relationships among data are represented by links. In this data model, graph data structure is used. It permits a record to have more than one parent.


Network data model


                                    Figure - Network Data model



This is an extension of the Hierarchical model. In this model data is organized more like a graph, and are allowed to have more than one parent node.

In this database model data is more related as more relationships are established in this database model. Also, as the data is more related, hence accessing the data is also easier and fast. This database model was used to map many-to-many data relationships.



Advantages of Network data model

  • The Network data model is also conceptually simple and easy to design.
  • In the network data model relationships like one-to-one and many-to-many are exist.
  • In the network data model without the owner, no member exists.
  • In the network database terminology, a relationship is a set. Each set comprises two types of record an owner record and a member record.


Hierarchical data model



In the hierarchical data, model data are represented by collections of records. Relationships among data are represented by links. In this model, tree data structure is used. There are two concepts associated with the hierarchical model segments types and parent-child relationships.


Hierarchical data model


                                Figure - Hierarchical Data model



This database model organizes data into a tree-like-structure, with a single root, to which all the other data is linked. The hierarchy starts from the Root data, and expands like a tree, adding child nodes to the parent nodes.


In this model, a child node will only have a single parent node.

This model efficiently describes many real-world relationships like index of a book, recipes etc.

In hierarchical model, data is organized into tree-like structure with one one-to-many relationship between two different types of data, for example, one department can have many courses, many professors and of-course many students.



Advantages of Hierarchical data model

  • Since the database is based on the hierarchical structure the relationships between the various layers are logically simple.
  • The hierarchical data model was the first database that offered the data security that is provided by DBMS.
  • The Hierarchical database model is based on the parent-child relationships.
  • It is very efficient one when the database contains a large number of one-to-many relationships.

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