Software design

✅ 1. What is Software Design?

📌 Definition:

Software Design is the process of defining the architecture, components, modules, interfaces, and data of a software system to satisfy specified requirements.

💡 In simple terms: Software design is the planning phase that shapes how the software will be built to ensure it meets user and business needs.

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🎯 2. Why is Software Design Important?

Reason	Benefit
Guides development	Provides a clear plan for developers to follow.
Improves quality	Ensures system is scalable, secure, and efficient.
Reduces risks and errors	Identifies potential issues early.
Facilitates communication	Aligns team understanding of system structure.
Saves time and cost	Avoids costly rework and design flaws.

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✅ 3. Key Activities in Software Design

Activity	Description
Understand requirements	Analyze and interpret system needs.
Define system architecture	Determine overall structure and technology stack.
Design components and modules	Identify how the system will be broken into parts.
Specify interfaces and data flow	Define how components interact and exchange data.
Consider non-functional requirements	Address performance, security, usability, etc.

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✅ 4. Levels of Software Design

Level	Description	Focus
1. High-Level Design (HLD)	Architectural design showing system structure.	Major components, technologies, data flow.
2. Low-Level Design (LLD)	Detailed design of components and modules.	Class diagrams, algorithms, interface details.

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📌 4.1 High-Level Design (HLD) Includes:

• System architecture diagram.

• Database design.

• Technology stack selection.

• Main components/modules and their responsibilities.

• Interaction between external systems.

Example: Diagram showing the relationship between a web app, database, and external APIs.

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📌 4.2 Low-Level Design (LLD) Includes:

• Class diagrams and object models.

• Detailed workflows.

• Data structures and algorithms.

• Component interaction details.

Example: UML diagram showing class relationships in a shopping cart system.

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✅ 5. Key Software Design Principles

Principle	Description
Modularity	Break system into manageable, independent parts.
Encapsulation	Hide internal details; expose only what is necessary.
Separation of Concerns	Each part should handle a distinct responsibility.
Single Responsibility Principle (SRP)	Every module/class should have one responsibility.
Reusability	Design components for reuse in different contexts.
Scalability	Design to handle growth in users/data.
Maintainability	Easy to update, fix, and extend.
Performance and Security	Ensure efficient, safe operations.

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✅ 6. Common Software Design Models & Diagrams

Model/Diagram	Purpose
Use Case Diagram	Shows system functionality from user perspective.
Class Diagram	Defines classes, attributes, methods, and relationships.
Sequence Diagram	Interaction flow between system components over time.
Component Diagram	Visualizes components and dependencies.
Entity-Relationship Diagram (ERD)	Models database schema and relationships.
State Diagram	Shows different states of an object and transitions.

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✅ 7. Tools Used for Software Design

Purpose	Tools
Diagramming and Modeling	Lucidchart, Microsoft Visio, Draw.io, Creately.
UML and Architecture Diagrams	StarUML, Enterprise Architect, Gliffy.
Wireframing and Prototyping	Figma, Balsamiq, Adobe XD.
Code-level Design	Visual Studio, JetBrains IDEs, Eclipse.

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✅ 8. Role of Business Analyst in Software Design

Activity	BA's Role
Bridge between business and technical teams	Ensure that design meets business needs.
Validate design decisions	Confirm that architecture supports requirements.
Participate in design discussions	Clarify requirements, suggest improvements.
Review diagrams and models	Ensure completeness and correctness.
Support during prototyping	Provide feedback on initial designs and mockups.

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✅ 9. Example of Software Design for an E-commerce System

Component	Design Consideration
User Interface (UI)	Responsive design, user-friendly navigation.
Product Catalog	Organized categories, search/filter features.
Shopping Cart Module	Add/remove items, manage quantities.
Payment Gateway Integration	Secure, support multiple payment methods.
Order Management	Track order status, history.
Database Design	Store user, product, order data efficiently.

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✅ 10. Summary of Software Design

Aspect	Explanation
Definition	Process of planning the software system structure.
Levels	High-Level Design (HLD), Low-Level Design (LLD).
Key Principles	Modularity, encapsulation, reusability, scalability.
Tools	Lucidchart, Visio, Figma, UML tools.
Role of BA	Ensure alignment between business needs and technical design.