Structured Design

Software Design, Cohesion and Coupling, Structured Design, Use Case Diagram, Sequence Diagram

Structured Design in Software Engineering

1. Definition

Structured Design is a software design technique that divides a large software system into smaller, manageable modules. Each module performs a specific task.

Example: A College Management System can be divided into Student Management, Faculty Management, Examination Management, and Library Management.

2. Diagram of Structured Design

3. Principles of Structured Design

1.                      Modularity: Dividing software into smaller modules.

Example: A banking system can be divided into account management, deposit, withdrawal, and transaction modules.

2.                      High Cohesion: Each module focuses on one related task.

3.                      Low Coupling: Modules have minimal dependency on one another.

4.                      Functional Independence

Each module should perform one well-defined function.

Modules should depend as little as possible on other modules.

Functional independence is achieved through high cohesion and low coupling.

5.                      Top-Down Design: Designing the main system first and then breaking it into smaller modules.

6.                      Simplicity: Making the software easy to understand and maintain.

7.                      Abstraction: Focus on the essential features of a system while hiding unnecessary details.

Describes what a module does rather than how it does it.

Example: A user withdraws money from an ATM without knowing the internal processing details.

8.                      Information Hiding: Each module should hide its internal data and implementation details.

Other modules should interact with it through clearly defined interfaces.

Example: A bank account module hides the account balance implementation and provides

functions to check or update it.

4. Advantages

·         Easy to develop and test.

·         Easy to maintain and modify.

·         Reduces software complexity.

·         Supports code reuse.

·         Makes debugging easier.

5. Disadvantages

·         Requires careful planning.

·         Changes affecting several modules may be difficult to manage.

·         Less suitable for some highly dynamic or object-oriented designs.

6. Short Answer for Exams

Structured Design is a systematic approach to software design in which a large system is divided into smaller modules. It improves modularity, maintainability, testing, and software quality.

Remember: Structured Design = Large System → Smaller Modules.

UML Diagrams-

UML Diagrams in Software Engineering

1. Definition

UML (Unified Modeling Language) is a standard visual language used to design, visualize, and document a software system.

It helps developers understand the structure and behaviour of a system before implementation. 

2. Types of UML Diagrams

UML diagrams are divided into two main categories.

Structural

Shows the structure of a system.

1. Class Diagram

2. Object Diagram

3. Component Diagram

4. Deployment Diagram

5. Package Diagram

Behavioral

Shows the behaviour of a system.

1. Use Case Diagram

2. Activity Diagram

3. State Machine Diagram

4. Sequence Diagram*

5. Communication Diagram*

*Sequence and Communication diagrams are interaction diagrams, a subgroup of behavioral diagrams.

UML 2.x defines 14 diagram types.