SOFTWARE DESIGN

Dr. Noman Islam

INTRODUCTION

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• Chapter introduces software design concepts.
• Focus on translating requirements into system structure.
• Covers architectural, component, and procedural design.
• Importance of design in software engineering.
• Ensures maintainability and scalability.
• Guides efficient implementation.
• Goal.
• Learn principles, techniques, and quality metrics.
• Understand design trade-offs.

DESIGN PROCESS OVERVIEW

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• Transform requirements into design.
• Identify components and their interactions.
• Define system architecture.
• Iterative and incremental process.
• Refine designs through iterations.
• Incorporate feedback continuously.
• Document design decisions.
• Maintain design rationale.
• Support communication with stakeholders.

DESIGN PRINCIPLES 1

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• Abstraction.
• Focus on essential details.
• Hide unnecessary complexity.
• Modularity.
• Divide system into cohesive modules.
• Facilitate reuse and maintenance.
• Separation of concerns.
• Keep unrelated functions separate.
• Enhances clarity and quality.

DESIGN PRINCIPLES 2

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• Information hiding.
• Encapsulate internal module details.
• Expose only necessary interfaces.
• Coupling and cohesion.
• Minimize inter-module dependencies.
• Maximize internal cohesion.
• Design simplicity.
• Keep designs as simple as possible.
• Avoid unnecessary complexity.

ARCHITECTURAL DESIGN

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• Define system’s high-level structure.
• Identify major components.
• Determine interactions and interfaces.
• Architectural styles.
• Layered, client-server, MVC, etc.
• Select based on requirements.
• Benefits of good architecture.
• Supports scalability and maintainability.
• Facilitates communication among teams.

COMPONENT-LEVEL DESIGN 1

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• Identify and define modules.
• Each module has clear responsibility.
• Define module interfaces.
• Design for reusability.
• Use generic and flexible components.
• Reduce duplication.
• Encapsulate data and functionality.
• Maintain abstraction.
• Prevent unintended interactions.

COMPONENT-LEVEL DESIGN 2

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• Cohesion in modules.
• Keep related functionality together.
• Simplify understanding.
• Coupling between modules.
• Minimize dependencies.
• Improve maintainability.
• Interface specification.
• Clear input/output contracts.
• Facilitate integration.

PROCEDURAL DESIGN

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• Design algorithms and procedures.
• Define step-by-step operations.
• Ensure correctness and efficiency.
• Flow of control diagrams.
• Visualize program logic.
• Identify loops and decisions.
• Mapping to modules.
• Align procedures with components.
• Support modular design.

USER INTERFACE DESIGN CONCEPTS

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• Design for usability.
• Simple and intuitive layout.
• Minimize user errors.
• Consistency in design.
• Uniform look and feel.
• Predictable interactions.
• Feedback mechanisms.
• Inform users of system state.
• Support error recovery.

DESIGN QUALITY ATTRIBUTES

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• Maintainability.
• Easy to modify or extend.
• Facilitates bug fixes.
• Performance.
• Efficient resource usage.
• Timely response to requests.
• Reliability and robustness.
• Minimize failures.
• Ensure graceful degradation.

DESIGN METRICS 1

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• Module size and complexity.
• Lines of code, function points.
• Assess understandability.
• Coupling and cohesion metrics.
• Low coupling desirable.
• High cohesion desirable.
• Code readability and clarity.
• Easier for maintenance.
• Reduces defects.

DESIGN METRICS 2

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• Reusability metrics.
• Assess module generality.
• Identify opportunities for reuse.
• Flexibility metrics.
• Ability to accommodate change.
• Support evolving requirements.
• Testability metrics.
• Ease of verification.
• Facilitates quality assurance.

DESIGN TRADE-OFFS

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• Performance vs maintainability.
• Optimized code may reduce readability.
• Simpler code may be slower.
• Coupling vs cohesion.
• Minimizing coupling may affect cohesion.
• Balance is required.
• Flexibility vs complexity.
• Highly flexible designs may be complex.
• Too simple may lack adaptability.

DESIGN PATTERNS OVERVIEW

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• Reusable solutions to common problems.
• Capture best practices.
• Provide standardized templates.
• Examples include Singleton, Observer, Factory.
• Solve common software challenges.
• Promote consistency.
• Benefits.
• Reduce design errors.
• Improve maintainability and communication.

CHAPTER SUMMARY

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• Design transforms requirements into system structure.
• Architectural, component, and procedural design.
• UI and behavioral aspects included.
• Design principles guide quality.
• Abstraction, modularity, information hiding.
• Coupling, cohesion, simplicity.
• Metrics and patterns support maintainability and reuse.
• Evaluate quality quantitatively.
• Apply proven solutions.