A data model is used to define a system's physical, logical, and view levels. In the database management system, we are familiar with a variety of data models (DBMS). In DBMS, data models are categorized into four types.
• Relational Model: The relational model represents data and the relationships between data by using a set of tables. Each table foundation includes numerous columns, each with its own name. Tables are sometimes referred to as relations. A record-based model is an example of the relational model. Record-based models get their name from the fact that the database is organized in fried format records of various sorts. Each table includes just one sort of record. Each record type has a set amount of fields or attributes. The table's columns match the record type's characteristics. The relational data model is the most extensively used data model, and it is the foundation of the great majority of modern database systems.
• Entity-Relationship Model: The entity-relationship (E-R) data model employs a collection of fundamental objects known as entities, as well as relationships between these entities. In the actual world, an entity is a "thing" or "object" that can be distinguished from other objects. In database architecture, the entity-relationship model is extensively employed.
• Object-Based Data Model: Object-oriented programming (particularly in Java or C++) has overtaken traditional software development methodologies. This resulted in the creation of an object-oriented data model, which may be seen as an extension of the E-R model with features of encapsulation, methods (functions), and object identity. The object-relational data model combines aspects of the object-oriented and relational data models.
• Semi-structured Data Model: The semi-structured data model allows for data definition in which individual data items of the same kind may have varying sets of characteristics. This is in contrast to the above-discussed data models, in which every data item of a specific kind must have the same set of properties. To express semi-structured data, the Extensible Markup Language (XML) is frequently used.
Historically, the network and hierarchical data models came before the relational data model. These models were inextricably linked to the underlying technology, complicating the process of modeling data.