HIERARCHICAL DATA MODEL
Was developed in the 1960s. The Hierarchical model was essentially born from the first mainframe database management system. It uses an upside-down tree to structure data. The top of the tree is the parent and the branches are children. Each child can only have one parent but a parent can have many children.
NETWORK DATA MODEL
In 1965 C.W. Bachman developed the first network data model to present complex data relationships more effectively than the hierarchical model. He tried to impose a database standard with his model and also wanted to improve database performance.
In 1971 the Conference on Data System Languages (CODASYL) officially defined the Network model. The network databases arrange its data as a directed graph and have a standard navigational language.
RELATIONAL DATA MODEL
The relational data model was introduced in 1970 by Edgar F. Codd. He worked for IBM. All data is represented as simple tabular data structures which the user can access through a high-level non-procedural language. In 1974 IBM proposed a new high-level non-procedural language - SEQUEL (renamed into SQL in 1990).
ENTITY RELATIONSHIP DATA MODEL
Dr. Peter Pin-Shan Chen introduced the entity relationship data model in 1976. It is a graphical representation of entities that became popular very quickly because it complemented the relational database model concepts.
BIOGRAPHY
Rob, P., Coronel, C. & Crockett, K. 2008. Database systems: design, implementation & management - international edition. UK: Gaynor Redvers-Mutton. pp37-51.
Danielsen, A. The evolution of data models and approaches to persistence in database systems. 1998. Available at: http://www.fing.edu.uy/inco/grupos/csi/esp/Cursos/cursos_act/2000/DAP_DisAvDB/documentacion/OO/Evol_DataModels.html. Accessed February 15, 2010.
Geekinterview.com. The Hierarchical Model. 2008. Available at: http://www.learn.geekinterview.com/it/data-modeling/the-hierarchical-model.html. Accessed February 15, 2010.
Geekinterview.com. Network Model. 2008. Available at: http://www.learn.geekinterview.com/it/data-modeling/network-model.html. Accessed February 15, 2010.
Geekinterview.com. Relational Model. 2008. Available at: http://www.learn.geekinterview.com/it/data-modeling/relational-model.html. Accessed February 15, 2010.
Geekinterview.com. A Look at the Entity-Relationship. 2008. Available at: http://www.learn.geekinterview.com/it/data-modeling/a-look-at-the-entity-relationship.html. Accessed February 15, 2010.
