CASE STUDY: Connie's Convenience Store

Lecture 18 applies the object-oriented analysis principles learned in preceding lectures to a comprehensive real-world case study: Connie's Convenience Store (Post-Office and Retail Point of Sale System). The case study details operational workflows: scanning barcodes, ringing sales items, managing inventory stock, processing cash and credit payments, printing itemized receipts, and closing register cash drawers. Students participate in identifying domain classes: Cashier, Customer, CashDrawer, Item, Sale, and SalesLineItem. The lecture demonstrates how to translate narrative customer business requirements into candidate class lists, evaluating which candidate entities warrant inclusion as persistent software objects and which represent transient hardware inputs. Structural relationships, including Generalization-Specialization inheritance hierarchies and Whole-Part aggregation assemblies, are modeled with precision. Dynamic interaction modeling demonstrates sequence diagrams, object lifelines, activation bars, and synchronous versus asynchronous message exchanges. Software architecture frameworks explore Kruchten's 4+1 view model, connecting logical, process, development, and physical architectural perspectives. Architectural styles, including layered hierarchies, repository patterns, client-server structures, and pipe-and-filter pipelines, are contrasted. Design pattern principles demonstrate how Gang of Four solutions, such as the Observer pattern, decouple subjects from observers to handle state changes. Professional coding style standards detail clear identifier naming, consistent indentation, layout structure, and self-documenting code conventions. Defensive programming practices illustrate safe file handling, resource leak prevention, and robust input validation in C++ and Java environments. Exception handling mechanisms demonstrate try-catch-finally blocks, structured error propagation, and eliminating silent runtime failures. Software portability guidelines detail isolating hardware-dependent logic, handling endianness, and standardizing primitive data type representations. Verification and validation activities contrast static software inspections and walkthroughs with dynamic code execution testing techniques. Testing paradigms emphasize finding defects systematically, contrasting developer testing mindsets with destructive verification approaches. Black-box testing strategies evaluate equivalence class partitioning and boundary value analysis to design high-coverage test case suites. White-box testing methodologies analyze control flow graphs, cyclomatic complexity calculations, and branch and statement coverage criteria. Unit testing protocols establish test drivers and stubs to isolate software modules and verify functional correctness before system integration.