Requirement Engineering-1

Lecture 3 initiates the study of Requirement Engineering, widely recognized as the most critical and challenging phase in software development. Requirement engineering encompasses the systematic discovery, documentation, and maintenance of a set of requirements for a computer-based system. The lecture details the devastating financial and organizational costs of requirements errors: a requirement defect corrected during maintenance can cost over one hundred times more than if resolved during initial analysis. Students explore requirement elicitation techniques, including stakeholder interviews, observation, questionnaires, and collaborative brainstorming. The curriculum analyzes functional requirements—which define specific services, inputs, behaviors, and outputs the system must execute—and contrasts them with non-functional quality constraints like performance, reliability, usability, and security. Coupling classifications, spanning content, common, control, stamp, and data coupling, are critically evaluated to eliminate structural dependencies. Cohesion levels, from coincidental and logical to communicational and functional cohesion, provide objective criteria for evaluating module quality. Object-oriented analysis using the Coad and Yourdon methodology illustrates identifying classes, responsibilities, attributes, and services. 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.