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Unit 5 SEP

 Software analysis and Design tools

Software Analysis and Design Tools are special computer programs that help developers and designers in every stage of making software. These tools make it easier to understand, plan, design, and document a software system so that the final product works well and meets user needs.

They help in collecting requirements by recording what users want, modeling the system using diagrams such as flowcharts and UML, and designing the structure and interface of the software.

These tools also help in creating documentation for clear communication, analyzing the design to find and fix problems early, and supporting teamwork by allowing different people to work together on the same project smoothly.

Introduction of ER Model

The Entity-Relationship (ER) Model is a conceptual model used to design and represent the logical structure of a database.
It shows entities, their attributes, and relationships among them.

Example: A Student enrolls in a Course — here Student and Course are entities, and "enrolls" is a relationship.

Components of ER Diagram

1.      Entity: A real-world object like Student, Course, or Employee.

2.      Attribute: A property of an entity, like StudentID or Name.

3.      Relationship: A link between entities, like a Student enrolls in a Course.

Importance of ER Diagrams

·         Easy to understand and use.

·         Helps in converting concepts into tables.

·         Represents real-world data visually.

·         No technical DBMS knowledge needed.



Relationship in ER Model

A Relationship in the ER Model shows the association or connection between two or more entities.
It defines how entities are related to each other in a database.

Example: A Student enrolls in a Course — “enrolls in” is the relationship.

Types of Relationships

1.      One-to-One (1:1)

o    One entity is related to only one entity of another type.

o    Example: Each person has one passport.

2.      One-to-Many (1:N)

o    One entity of a type is related to many entities of another type.

o    Example: One teacher teaches many students.

3.      Many-to-One (N:1)

o    Many entities are related to one entity of another type.

o    Example: Many students study in one department.

4.      Many-to-Many (M:N)

o    Many entities of one type are related to many entities of another type.

o    Example: Students enroll in many courses, and each course has many students.

 
Attributes

·  Attributes are properties that describe an entity.
Example: Student has Roll_No, Name, and DOB.

·  Key Attribute uniquely identifies each entity.
Example: Roll_No of a student.

·  Composite Attribute is made up of smaller attributes.
Example: Address → Street, City, State.

·  Multivalued Attribute holds more than one value.
Example: Phone_No (student may have two numbers).

·  Derived Attribute is calculated from other attributes.
Example: Age from Date of Birth (DOB).

Types of Entities

1.      Strong Entity:

o    Has its own key attribute for identification.

o    Example: Employee (identified by Employee_ID).

o    Symbol: Single rectangle.

2.      Weak Entity:

o    Cannot be identified without another entity.

o    Depends on a Strong Entity for identification.

o    Example: Dependent of an Employee.

o    Symbol: Double rectangle (with double diamond for identifying relationship).

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