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.
Definition. Software reuse is building new software by incorporating existing software artifacts — components, libraries, frameworks, design patterns, generators, or even whole systems — rather than developing every part from scratch.
Benefits.
Reduced cost and time, since the reused artifact does not need to be (re)built.
Improved reliability, because a component that has already been exercised in prior use has an established track record and its defects have already been found and fixed by earlier users.
Reduced process risk, since the effort to integrate a known component is easier to estimate accurately than the effort to build new, unproven code.
Effective use of specialist effort, since reuse concentrates the cost of building a genuinely good component into a single effort, amortized across every project that reuses it.
Standards compliance, since a widely-reused component may already meet accessibility, security, or regulatory standards the new project would otherwise have to satisfy from scratch.
Challenges (of producing reusable software).
The cost of building reusability itself, since a genuinely reusable, well-documented, sufficiently general component is more expensive to build than a one-off equivalent, and that extra generality is sometimes never exercised (over-engineering risk) — generalizing an operation for hypothetical future callers takes real, extra design and testing effort beyond what a single, specific use would need.
Loss of control over evolution once published, since a component intended for reuse by other teams/projects must maintain a stable interface going forward, which constrains how freely its own producer can later change it.
Documentation and support burden, since a producer of a reusable component must document its contract, assumptions, and limits precisely enough for teams who were never involved in building it to use it correctly — a burden a one-off internal component does not carry.
Predicting the right level of generality, since building for a narrower set of future needs than actually materializes limits reuse value, while over-generalizing wastes effort on flexibility nobody uses; getting this right requires anticipating requirements the producer may never see directly.
Cross-boundary tool support gaps, since debugging and static analysis tools often stop being effective at the boundary of a component whose internals a later reusing team treats as opaque.
