Systems Development Foundations: Models, Methodologies & SDLC

TAKEAWAYS:

• Understand the SDLC phases (planning, analysis, design, implementation, maintenance) and how they form a structured approach to system development.
• Compare process models (waterfall, iterative, incremental, spiral, agile) and identify their strengths/weaknesses for real-world projects.
• Learn methodologies (structured, OO, SOA) and their impact on system design, documentation, and maintenance.
• Define systems classification (manual vs. automated, transaction vs. information) and assess feasibility (technical, economic, operational, legal).
• Recognize stakeholder roles (users, developers, managers) and their influence on system success.
• Apply process modeling (DFD, UML) to visualize system workflows and requirements.

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1. Systems Development Life Cycle (SDLC)

The SDLC is a structured framework for developing information systems. It ensures systematic planning, analysis, design, implementation, and maintenance. The phases are sequential but may overlap in iterative models.

SDLC Phases

Key Activities in Each Phase

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Worked Example: Daraz Order Processing System

Scenario: Daraz (Nepal’s e-commerce giant) needs a new order management system.

• Planning: Scope = real-time order tracking, inventory updates, customer notifications.
• Analysis: DFD shows 3 processes (order placement → payment → delivery).
• Design: Database schema for Orders, Customers, Products; API for third-party logistics.
• Implementation: Python backend, React frontend, AWS hosting.
• Maintenance: Monthly performance reviews, bug fixes for peak sales (e.g., Dashain).

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2. Process Models in SDLC

Process models define how development is executed. Each has trade-offs in flexibility, cost, and risk.

Comparison of Process Models

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Real-World Example: eSewa’s Agile Approach

eSewa (Nepal’s fintech leader) uses Agile for its mobile app:

• Sprints: 2-week cycles for features like QR payments or loan services.
• Daily standups: Dev teams sync on bugs (e.g., failed transactions during Dashain).
• Customer feedback: Direct input from merchants using the app.

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3. Systems Methodologies

Methodologies provide how-to frameworks for analysis and design.

A. Structured Methodology

• Focus: Top-down approach, modular design.
• Tools: Data Flow Diagrams (DFD), Entity-Relationship Diagrams (ERD).
• Example: Designing a bank loan processing system (see below).

B. Object-Oriented (OO) Methodology

• Focus: Objects (e.g., Customer, Order) with attributes/methods.
• Tools: UML diagrams (class, sequence, use case).
• Example: WhatsApp’s message object has:
  • Attributes: sender, receiver, timestamp, status (read/delivered).
  • Methods: send(), delete(), encrypt().

C. Service-Oriented Architecture (SOA)

• Focus: Modular services (e.g., payment gateway, inventory) that communicate via APIs.
• Example: Daraz uses:
  • Payment Service: Integrates with Khalti/Nepal Bank Limited.
  • Inventory Service: Syncs with suppliers in real time.

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4. Systems Classification

Systems can be categorized based on automation level, purpose, and scope.

Classification Table

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5. Feasibility Study

Before development, assess 4 key factors:

1. Technical: Can the system be built with current tech? (e.g., NEPSE’s blockchain trial).
2. Economic: Cost vs. benefits (e.g., NTC’s fiber-optic upgrade ROI).
3. Operational: Will users adopt it? (e.g., eSewa’s QR code training).
4. Legal: Compliance with laws (e.g., data privacy for banks).

Worked Example: Ncell’s 5G Feasibility

• Technical: 5G towers require new infrastructure (feasible but costly).
• Economic: $50M investment vs. $20M/year revenue boost.
• Operational: Customer readiness (low initial adoption).
• Legal: Spectrum license approval from government.

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6. Stakeholder Analysis

Stakeholders influence system success. Key groups:

• Users: End customers (e.g., Daraz shoppers).
• Developers: IT teams (e.g., Khalti’s backend engineers).
• Managers: Project leads (e.g., NTC’s IT director).
• Regulators: Government bodies (e.g., Nepal Rastra Bank for fintech).

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In the Real World

1. eSewa’s Agile + SOA

   • Idea: Agile sprints + SOA for modular services (payments, loans).
   • How: Each service (e.g., LoanService) is independently deployable, reducing downtime during festivals like Dashain.

2. Daraz’s Incremental Delivery

   • Idea: Incremental model for e-commerce features.
   • How: Started with product listings → added cart → then payments → now AI recommendations.

3. NTC’s Waterfall for Billing System

   • Idea: Waterfall for stable, regulated systems.
   • How: NTC’s old billing system used a linear approach because requirements (tax laws, user data) rarely changed.

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Exam Tip

1. SDLC Questions:

   • Expect phase-wise questions (e.g., “What DFDs are created in Analysis?”).
   • Trace examples: Link a real system (e.g., Khalti) to SDLC phases.

2. Process Models:

   • Compare 2 models in exams (e.g., “Why did Pathao choose Agile over Waterfall?”).
   • Draw diagrams: Always sketch a mini-DFD or UML class diagram if asked.

3. Methodologies:

   • Structured vs. OO: Know when to use each (e.g., OO for WhatsApp’s objects).
   • SOA: Explain APIs and service independence (e.g., Daraz’s payment service).

4. Feasibility:

   • Calculate ROI for economic feasibility (e.g., “NTC’s fiber upgrade costs $50M; projected savings are $15M/year. Is it feasible?”).
   • Non-technical factors: Always mention legal/operational constraints.

5. Stakeholders:

   • Role-play questions: “How would you handle a conflict between Ncell’s IT team and regulators?”
   • Diagrams: Draw a stakeholder map for any given system (e.g., hospital management system).

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Key Formula to Remember:

• Return on Investment (ROI): $$\text{ROI}=\frac{\text{Net Benefit}}{\text{Cost}}\times 100\%$$ Example: For NTC’s fiber upgrade: $$\text{ROI}=\frac{15\text{M}-50\text{M}}{50\text{M}}\times 100\%=-70\%(\text{Not feasible without subsidies})$$