25-Comp-B11 Advanced Software Design · December 2019
Question 1 of 28: Agile Methodologies vs. Conventional Document-Driven Process Models
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Notes on this paper
17-Comp-B11 Advanced Software Design — National Exams, December 2019. 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, design principles, testing, 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 and the "program to an interface, not an implementation" / "favor object composition over class inheritance" principles; Sebesta, Concepts of Programming Languages (12th ed.) — polymorphism, dynamic binding, visibility, and multiple inheritance semantics; Bertrand Meyer, Object-Oriented Software Construction — design by contract, preconditions/postconditions/class invariants; Barbara Liskov's 1987 substitutability paper for Question 12; Karl Wiegers, Software Requirements (3rd ed.); Myers, The Art of Software Testing, for Question 6.
PART I — General Principles (answer any 5 of 7)
Question 1: Agile Methodologies vs. Conventional Document-Driven Process Models (Part I)
Agile methodologies (e.g. Scrum, XP) develop software in short, time-boxed iterations that each produce working, potentially-shippable software, with requirements refined incrementally through continuous customer collaboration rather than frozen up front. Advantages: fast feedback lets defects and wrong assumptions surface early; the process adapts naturally to changing requirements instead of resisting them; working software is available from the first few iterations, reducing the risk of building the wrong system. Disadvantages: the lack of a fixed, up-front scope makes long-range budgeting and fixed-price contracting difficult; it depends on continual, engaged customer availability that is not always achievable; and the light-weight documentation trail is often insufficient for safety-critical or heavily-regulated systems that must be formally audited.
Conventional document-driven process models (e.g. Waterfall, the V-model) execute a sequence of phases — requirements, design, implementation, verification, maintenance — each producing a formal document that is reviewed and signed off before the next phase begins. Advantages: clear milestones and deliverables support fixed-price contracts and external audits; the paper trail gives strong traceability from requirement to test case, which is valuable for regulated or safety-critical domains; progress is easy to report against a plan. Disadvantages: requirements are effectively frozen early, so a misunderstanding discovered late is expensive to correct; no working software exists until near the end of the project, deferring the discovery of integration and usability problems; and the model copes poorly with genuinely evolving requirements.
