Systems Analysis and Design (SAD): SDLC Phases, Agile vs Waterfall, and DFD Modeling

Understanding Systems Analysis and Design

Developing robust, scalable software requires structured engineering practices. Systems Analysis and Design (Unit 7) explores how IT professionals identify organizational problems, analyze business requirements, and design technological solutions.

The Software Development Life Cycle (SDLC)

The SDLC is a systematic framework divided into defined phases:

1. Preliminary Investigation & Feasibility Study: Evaluates Technical, Economic, Operational, and Legal feasibility (TELOS framework).
2. Requirement Analysis: Gathers user expectations through interviews, questionnaires, document inspection, and observation. Produces the Software Requirements Specification (SRS).
3. System Design: Architects the system blueprint, including database schemas, user interfaces, system architecture, and Data Flow Diagrams.
4. System Implementation & Coding: Developers write and compile source code according to the design specifications.
5. Testing: Verifies that the system functions correctly and meets all requirements without defects.
6. Deployment & Conversion: Transitions from the old system to the new system (Direct, Parallel, Phased, or Pilot conversion).
7. Maintenance: Ongoing corrective, adaptive, perfective, and preventive updates.

Data Flow Diagrams (DFDs)

DFDs graphically represent how data moves through an information system:

• Process (Rounded Rectangle / Circle): Transforms incoming data flows into outgoing data flows.
• Data Store (Open-ended Rectangle): A repository of data (database table or physical file).
• External Entity (Square / Rectangle): An external source or sink of data outside the system boundary.
• Data Flow (Arrow): Shows the direction in which data packets or information travel.

Software Development Methodologies: Waterfall vs Agile

Feature Waterfall Model Agile Methodology Approach Sequential, linear stages Iterative, incremental sprints Flexibility Rigid; changes late in cycle are costly Highly adaptive to evolving requirements Customer Involvement Primarily at beginning and end Continuous collaboration throughout sprints Delivery Single final product at end of project Frequent working software increments (every 2-4 weeks)