Unit II – Software Process & Requirements Modeling

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 Agility Principles (12 Principles of Agile)

The Agile Alliance defines 12 principles for achieving agility:

1. Customer Satisfaction → Deliver valuable software early & continuously.

2. Welcome Change → Even late in development.

3. Frequent Delivery → Weeks, not years.

4. Business + Developers Together → Daily collaboration.

5. Motivated Individuals → Support, trust, empower them.

6. Face-to-Face Conversation → Best way to share ideas.

7. Working Software → Primary measure of progress.

8. Sustainable Development → Maintain a constant pace.

9. Technical Excellence → Continuous focus on quality.

10. Simplicity → Do only what’s essential.

11. Self-Organizing Teams → Best designs emerge naturally.

12. Reflection & Improvement → Regularly tune and adapt.

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 The Politics of Agile Development

There’s a heated debate between:

• Traditionalists → Focus on documentation first, then software.

• Agilists → Focus on working software first, adjust later.

 Reality: Both sides have merits. Too much documentation slows projects; no documentation causes confusion.

 Requirement Analysis

Requirement analysis = understanding what the system should do.

It answers:

• What interactions occur with users?

• What objects are manipulated?

• What functions must exist?

• What behaviors should occur?

• What interfaces are required?

• What constraints apply?

Focus on WHAT, not HOW.

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 Domain Analysis

Domain Analysis = Identify, analyze, and specify common requirements in a specific application domain.

• Helps in reuse across projects.

• In Object-Oriented Domain Analysis (OODA) → Find common objects, classes, frameworks that apply to multiple systems.

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Requirements Modeling Approaches

There are 4 modeling approaches:

1. Scenario-Based Elements

   • Show user interaction step by step.

   • Example: “User enters password → System validates → Grants access.”

2. Class-Based Elements

   • Show objects, operations, relationships.

   • Example: UML Class diagrams.

3. Behavioral Elements

   • Show how events affect system state.

   • Example: State diagrams.

4. Flow-Oriented Elements

   • Show how data flows through system functions.

   • Example: Data Flow Diagrams (DFD).

 Data Modeling Concepts

1. Data Flow Model

• Context-Level DFD → Big picture view (SafeHome system interacting with user & sensors).

• Level 1 DFD → Break into subsystems (monitoring, alarms, logs).

• Level 2 DFD → Details for specific processes (like “monitor sensors”).

2. Control Flow Model

• List all sensors read by the software.

• List all interrupts (e.g., alarm triggered).

• List all switches actuated by operator.

• List all data conditions.

• Define system states and transitions.

Example: SafeHome → States: Idle → Armed → Triggered → Reset.

         Idle → system is inactive

         Armed → system is monitoring

         Triggered → alarm is activated

         Reset → system returns to idle