What is Semantic Data models in Dbms , Advantages

What is Semantic Data models ?

The Semantic Data Model (SDM), like other data models, is a way of organizing data to represent it in a logical way.
SDM differs from other data models, however, in that it focuses on providing more meaning of the data itself, rather than primarily on the relationships and attributes of the data.
This model provides a high-level understanding of the data by abstracting it further away from the physical aspects of data storage.

In semantic data model, an entity represents some aspect or item in the real world, such as an EMPLOYEE. These entities in SDM focus on types, which are more general, instead o sets of data. For instance, a semantic data model entity type might be PERSON, which provides an elementary category that can be easily understood. In a relational model, however, you might end up with a number of different tables including- person, spouse, children, house, ana Each of these things represents part of what makes up the person, but with SDM, the cPSON is the whole entity, rather than breaking it down into parts.

In this way, an entity in SDM is very similar to a domain. Therefore, inside this domain of PERSON, PERSON there would be a list of names of people that are to be represented by the data. objects in this domain would then point to specific instances of a person that are The objects in this represented by eacn person entity. For example, the domain PERSON contains name Rahul, repre Sunny, Jimmy, and John. Each of these names points to a specific object instance of PERSON, so that Rahul points to a record giving detail about Rahul, such as name, gender, or marital status, and so on for each of the entities listed under PERSON.

What is Entity-Relationship Model (E-R MODEL) ?

Entity-Relationship Model (E-R Model) is a high-level conceptual data model developed by Peter Chen in 1976 to facilitate database design. Conceptual Modeling is an important phase in designing a successful database. A conceptual data model is a set of concepts that describe the structure of a database and associated retrieval and updation transactions on the database. The E-R model is the generalization of the earlier available commercial models ike the Hierarchical and the Network Model. So to sum up, the Entity-Relationship (E-R) Model is based on a view of a real world that consists of set of objects called entities and relationships among entity sets which are basically a group of similar objects. The relationships between entity sets is represented bya named E-R relationship and is of 1:1, 1: N or M: N type which tells the mapping from one entity set to another.

A basic component of the E-R model is the Entity-Relationship diagram which is used to visually represent data objects and the relationships between them.

Features of the E-R Model :-

The E-R diagram used for representing E-R Model can be easily converted into relations (tables) in relational model.
The E-R Model is used for the purpose of good database design by the database developer so to use that data model in various DBMS.
It is helpful as a problem decomposition tool as it shows the entities and the relationship between those entities.

Entities and Attribute :-

The basic object that the ER model represents is an entity, which is a "thing" in he real world with an independent existence. An entity may be an object with a physical existence- a particular person, car, house etc. or it may be an object witha conceptual existence- a company, a job, or a university course.
Each entity has attributes- the particular properties or characteristics that describe it. For example, an EMPLOYEE entity may be described by its attributes- rname, age, address, salary, and job. A particular entity will have a value for each of its attr+butes. The attribute values that describe each entity become a major part of the data stored in the database.