Use Case and Class Diagrams for a Personal Financial Management Application: 25-Comp-B11 Advanced Software Design, December 2019, Q4

Question 4 of 28: Use Case and Class Diagrams for a Personal Financial Management Application

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 4: Use Case and Class Diagrams for a Personal Financial Management Application (Part I)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

Given. A single actor (the User) must be able to add, edit, calculate (a running balance/summary), save, and load personal financial transaction data.

Use case diagram: one actor, five use cases derived directly from the stated capability list.

Class diagram: TransactionManager coordinates a collection of Transaction objects and delegates persistence to FileStorage.

From use cases to classes. Each use-case bubble maps directly onto a method of TransactionManager, the controller class that owns the in-memory list of transactions: Add/Edit Transaction → add()/edit(), Calculate Summary → calculateBalance(), Save/Load Data → save()/load(), the latter two delegated to a separate FileStorage class so persistence logic (file format, I/O) is not entangled with the in-memory business logic. Each individual financial record is its own Transaction object (amount, date, category) rather than a raw row of fields scattered across the manager, so a transaction can be validated, displayed, or serialized as a single unit — the 0..* association between TransactionManager and Transaction is exactly the "supports a user to add/edit" requirement expressed structurally.