Question

What is a use case, and what is its purpose?

Define the term entity and give an original example.

Define the term attribute and give three examples for the entity in question (2).

Define the term relationship and give an original example for the entity in question (2).

Answer 1

1)

A use case describes how a person actually uses a process or system will accomplish a goal.

It is associated with software systems. Use case can be described through a series of written steps. Three main parts that a use case must contain:

1. Actor, which is the user of the system, it can be a single person or a group of people, interacting with a process

2. System, It is the process that is needed to accomplish the final outcome

3. Goal, which is the purpose user outcome

Use case begins with a user's goal and ending when that goal is successful.

Use case diagram helps capture the dynamic aspect of a system

The purpose of the use case diagrams is to provide the high level view of the system and it     specify the requirements.

2)

An entity can be defined as an object that exists. An entity can be a thing, an individual, place, or object. An entity can be considered as the key element in all relational databases.

For example,

Consider student as an entity. This student entity has certain characteristics called attributes. Student_name is an attribute of that entity.

Department is an entity.

Course is an entity

3)

Attributes are the describing characteristics or properties of entities. An entity consist of any number of attributes. One of the attributes is termed as the primary key.

· Consider student entity, the attributes of this entity are student_name, student_id, roll_no, course_id, department_id

· Consider department as an entity, attributes are department_name, department_id

· Consider course as an entity, attributes are course_name, department, course_id

4)

A relationship can be defined as the association that exists among one or more entities. Relationship is represented by using a collection of inter-related tables. Entity Relationship Model depicts data as Entity set, Relationship set and Attribute.

Consider 3 entities Student, course and department

It is possible to define a relationship among these entities.

The entity student is related to course and department. Student entity contain course_id and department_id. i.e.,one table contains the primary key of other tables.