Flat Model:
A flat file can contain a plain text or mixed text and binary file which usually contains one record perline the single fields separtaed by delimiter's e.g comma's

Hierarchical Model:
Database resembles a tree like structure.
Implies a single upward link in each record to describe the nesting, and a sort field to keep the records in a particular order in each same-level list.
To create links between the records, the hierarchical model uses Parent Child Relationships.
This structure allows one 1:N relationship between two types of data.
One limitation of the hierarchical model is its inability to efficiently represent redundancy in data.
E.g. : Used in IBM’s IMS DBMS


Network Model:
The network model permitted the modeling of many-to-many relationships in data
The network model organizes data using two fundamental constructs, called records and sets.
Records contain fields . Sets define one-to-many relationships between records: one owner, many members. A record may be an owner in any number of sets, and a member in any number of sets.
The network model is able to represent redundancy in data more efficiently than in the hierarchical model.
E.g. : Used in IDS and IDMS


Relational Model:
The basic data structure of the relational model is the table, where information about a particular entity (say, an employee) is represented in columns and rows (also called tuples).

E.g. : IBM’s DB2, Informix, Oracle, Sybase, Microsoft’s Access, FoxBase, Paradox, Tandem ..


Object Oriented Model
Recent development, Stores data and methods to act on the data
E.g. : Objectstore and Versant

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