25-Comp-B11 Advanced Software Design · December 2014
Question 12 of 26: Design Goals in System Design
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Notes on this paper
98-Comp-B11 Advanced Software Design — National Exams, December 2014. 3 hours, closed book, no calculator permitted. The paper is organized into five parts, and candidates were instructed to answer any three (3) questions in Part I, any four (4) in Part II, any four (4) in Part III, any two (2) in Part IV, and any two (2) 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 15 questions actually marked (3+4+4+2+2 of 26) each count for 100/15 ≈ 6.7% of the paper. All 26 questions are answered below for completeness.
Reference texts: Sommerville, Software Engineering (10th ed., Pearson) — software processes, requirements engineering, agile methods, design principles; 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 — structural/behavioural pattern catalogue (Proxy, Bridge, Strategy, Observer, Template Method, Composite, etc.); Sebesta, Concepts of Programming Languages (12th ed.) — polymorphism, dynamic binding, inheritance and language-level object semantics (also underpins the Java/C++ discussion in Part V); Brown, Malveau, McCormick & Mowbray, AntiPatterns: Refactoring Software, Architectures, and Projects in Crisis — anti-pattern catalogue (Question 18). Bertrand Meyer's Object-Oriented Software Construction is cited by name where the paper's own vocabulary (design by contract, open–closed principle) originates there; Barbara Liskov's 1987 substitutability paper is likewise cited by name for Question 11.
PART I — General Principles (answer any 3 of 5)
Question 12: Design Goals in System Design (Part II)
Typical design goals the literature (and practice) recognizes include: performance (throughput/latency), maintainability, reliability/robustness, security, reusability (Question 8), portability, cost and time-to-market, usability, and testability. A real project virtually never maximizes all of these simultaneously — several trade off directly against one another (e.g., extensibility and flexibility, discussed for MVC in Question 19, typically cost some raw performance versus a tightly-coupled, non-extensible design), so a design alternative is chosen because it best satisfies the goals that have been PRIORITIZED for this particular project, not because it is objectively best on every axis.
Who sets them. Design goals are derived from the non-functional requirements captured during requirements analysis (Questions 2 and 4), which themselves originate from several distinct stakeholder groups: the customer/business sponsor (cost, time-to-market, usability), end users (response time, usability), operations and maintenance staff (maintainability, supportability), regulators and standards bodies (safety, security, and compliance — particularly salient for EGBC-regulated engineering work), and the development organization itself (reusability across a product line, portability to reduce future platform-migration cost). The lead designer/architect then TRANSLATES these into concrete, prioritized, and where possible quantified design goals, and is responsible for surfacing the trade-offs explicitly back to stakeholders when goals conflict (e.g., "meeting the additional security-review requirement will delay delivery by three weeks").
