Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Notes on this paper
98-Comp-B11 Advanced Software Design — National Exams, May 2016. 3 hours, closed book exam with one aid sheet allowed (written on both sides), no calculator permitted. The paper is organized into five parts, and candidates were instructed to answer any five (5) questions in Part I, any three (3) in Part II, any four (4) in Part III, any two (2) in Part IV, and any five (5) in Part V — only the first questions answered, in each part, as they appear in the answer book are marked. All questions carry equal weight, so the 19 questions actually marked (5+3+4+2+5 of 28) each count for 100/19 ≈ 5.26% of the paper. All 28 questions are answered below for completeness.
Reference texts: Sommerville, Software Engineering (10th ed., Pearson) — software processes, requirements engineering, agile methods, design principles, dependability; Pressman, Software Engineering: A Practitioner's Approach (9th ed.) — supplementary process and quality coverage; Gamma, Helm, Johnson & Vlissides (GoF), Design Patterns: Elements of Reusable Object-Oriented Software — creational/structural/behavioural pattern catalogue (Singleton, Proxy, Template Method, Observer, etc.); Sebesta, Concepts of Programming Languages (12th ed.) — polymorphism, dynamic binding, inheritance and language-level object semantics; Bertrand Meyer, Object-Oriented Software Construction — design by contract, preconditions/postconditions/invariants, the open–closed principle; Barbara Liskov's 1987 substitutability paper for Question 11; Rogers, Sharp & Preece, Interaction Design, and Nielsen, Usability Engineering, for Question 21's HMI-specific non-functional requirements; Myers, The Art of Software Testing, for Question 28's boundary value analysis.
The Waterfall model is a linear, single-pass process: requirements → design → implementation → testing → deployment → maintenance, each phase completed and formally signed off before the next begins. It is plan-driven — the full scope and schedule are committed at the start — and carries no explicit, repeated risk-analysis step; a phase is, in principle, never revisited once its deliverable is approved.
The Spiral model (Boehm, 1986) is risk-driven and explicitly iterative: the project proceeds around a spiral of cycles, each cycle repeating the same four activities — (1) determine objectives, alternatives, and constraints for this cycle; (2) evaluate alternatives and identify/resolve the cycle's risks, typically via prototyping or analysis; (3) develop and verify the next-level product; (4) plan the next cycle. Each pass produces a more complete or better-understood version of the system, and the radius of the spiral (effort committed) grows only as risk is progressively retired.
Differences. Waterfall is sequential with a single delivery at the end; Spiral is cyclical, revisiting requirements, design, and risk assessment on every loop and can deliver prototypes or partial products along the way. Waterfall has no dedicated risk-analysis activity; Spiral makes risk identification and mitigation the organizing principle of every cycle — the amount of process rigour applied to a given cycle scales with that cycle's assessed risk, rather than being fixed in advance. Waterfall commits the full plan up front; Spiral re-plans after every cycle based on what the risk analysis found, so scope and schedule are adjusted progressively rather than fixed at project start.
Similarities. Both are plan-driven, phase-structured models (neither is as lightweight or continuously customer-collaborative as agile methods) — each Spiral cycle internally follows a mini-waterfall-like sequence (understand objectives, build, verify) before looping. Both use defined milestones/reviews to gate progress, and both document deliverables at each phase or cycle boundary. In fact, Waterfall can be viewed as a DEGENERATE special case of Spiral: a Spiral process with exactly one cycle and no explicit risk-analysis activity collapses to Waterfall's single sequential pass — Spiral generalizes Waterfall by wrapping the same sequential development activities in a repeated, risk-driven outer loop.
