There are 4 data models in DBMS
Relational Data Model
- Edgar F.Codd described the model in 1969.
- Data are designed using rows and column within a table. So data and in between relationships are represented using these models.
- In this model tables are called as relations.
- It is a widely used models for commercial data processing applications.
Entity-Relationship Data Model
- Data in this model is logically represented asobjects and relationships among them.
- Objects in this models are known as entities and relationship among these entities.
- Peter Chen designed this relationship model. This relationship model is used in database desigining.
- Set of attributes describe entities and set of same type of entities is known as Entity Set and set of the same type of relationship is known as relationship set.
Object-based Data Model
- Object based model is an extension of ER model with the notions of functions, encapsulations and object identity.
- Structure and collection types are supported in this model.
- Database systems following the object oriented approach were developed during 1980.
- In this model objects are nothing but data carrying its properties.
Semistructured Data Model
- This model is different from other 3 models.
- Data specification is allowed in this model where the individual data items of the same type have different attribute sets.
- Semi Structured data is widely used and represented by XML(Extensible Markup Language).
- When XML was developed for desiging the mark up information to the text document, it gains importance because of its applcation in the exchange of data.