Components of Data Modeling

• Components of Data Modeling

Data modeling is the process of identifying various data objects and
relationships between them.
The objects that are used to represent data items in a data model are called components of data modeling. There are three important components of data modeling. These are entities, attributes, and relationships. Following is a brief description of these components.

• Entities

An entity is a person, place, object, event, or concept about which data is collected and maintained. It is the real world thing about which data is collected and stored in a database) Some examples of entities include:

PERSON PLACE

OBJECT

EVENT

CONCEPT :

student, customer, employee, patient department, city, province, country automobile, machine, building sale, registration, renewal
accounting, course

• Attributes

An attribute is a property (or characteristic) of an entity. An entity may have many attributes. However, only those attributes are used which are of interest to database users.

For example, in an EMPLOYEE entity, the attributes of interest to an organization may be Name, Date of Birth, Hiring Date, ID Card Number, and Address of employees. As human beings, employees have many additional attributes, such as hair color, eye color, etc., which may not be of any use for an organization.

Some entities and their attributes commonly used in databases are:

STUDENT EMPLOYEE :

BOOK CUSTOMER:

Std-ID, Std-Name, Address, Phone Number Empid, Emp-Name, Skill, Job Code Author, Title, Price, Quantity, Edition, ISBN Cust-Name, Cust-ID, Address, Phone- Number

• Relationships

A relationship between two ent es indicates how these entities are related or connected to each other. The entities may be related to one another in different ways.) For example, the two entities BOOK and BOOKSTORE may have the following relationships between them:
stocks
sells
BOOKSTORE orders BOOKSTORE displays BOOKSTORE BOOKSTORE BOOKSTORE returns
BOOK BOOK BOOK BOOK
BOOK