25-Comp-B11 Advanced Software Design · Undated paper
Question 18 of 28: MVC Architecture for a Personal Address Book Application
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Notes on this paper
17-Comp-B11 Advanced Software Design — National Exams, May 2019. 3 hours, closed book exam with two aid sheets 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, reuse; Pressman, Software Engineering: A Practitioner's Approach (9th ed.) — supplementary process/metrics/quality coverage; Gamma, Helm, Johnson & Vlissides (GoF), Design Patterns: Elements of Reusable Object-Oriented Software — pattern-language structure, the GoF pattern catalogue, and the "favor object composition over class inheritance" / "program to an interface, not an implementation" principles; Sebesta, Concepts of Programming Languages (12th ed.) — polymorphism, dynamic binding, visibility, encapsulation, interfaces; Bertrand Meyer, Object-Oriented Software Construction — design by contract, preconditions/postconditions/class invariants; Barbara Liskov's 1987 substitutability paper for Question 12; Stroustrup, The C++ Programming Language, for friend/access-control semantics (Question 25).
Question 12 prints “Liskpv substitution principle”, a typo in the paper; it is answered as the Liskov substitution principle.
PART I — General Principles (answer any 5 of 7)
PART IV — GUI Design (answer any 2 of 4)
Question 18: MVC Architecture for a Personal Address Book Application (Part IV)
AddressBookModel holds contact data and business logic; ContactListView displays it and forwards user actions to AddressBookController; AddressBookController updates the Model, which in turn notifies the View.
Extensibility — HELPS. Because AddressBookModel has no dependency on any specific view technology, a new view (e.g. a mobile UI or a plain-text export view) can be added by writing a new View class that observes the same Model, with zero change to the business logic. A new Controller can likewise be added to support a new input mechanism (e.g. voice command) without touching the Model.
Response time — may HURT (slightly). The extra indirection — the Controller mediating user actions into Model updates, and the Model notifying the View rather than the View reading data directly — adds a small amount of call/notification overhead compared to a single monolithic class handling everything inline. For a desktop-scale personal address book this overhead is negligible; it would only matter in a genuinely latency-critical rendering loop, which this application is not.
Modifiability — HELPS. Because presentation (View) and business logic (Model) are separated, redesigning the contact list's visual layout requires changing only ContactListView, and changing a contact-validation rule requires changing only AddressBookModel — each kind of change is confined to the layer responsible for it, rather than requiring a change to be threaded through a single undivided class.
