Introduction to Software Requirements Engineering – Part 1

Software Requirements Engineering Introduction

Software requirements engineering is the discipline of collecting and defining what services a system should provide. It focuses on assessing business feasibility, eliciting and analyzing needs, formalizing them into specifications, and verifying that they meet the customer's expectations.

The process is not strictly sequential; it is an iterative activity where user needs are repeatedly captured, refined, and validated, and system requirements are evolved in parallel.

User and System Requirements

Requirements are typically divided into two levels of detail: user requirements, which are high‑level statements for stakeholders, and system requirements, which provide the detailed specifications needed by developers, architects, and testers.

Functional vs. Non‑Functional Requirements

Functional requirements describe the primary services the system must deliver, often expressed in abstract user‑oriented language. Detailed system functional requirements specify inputs, processing, responses, and expected outputs.

Non‑functional requirements impose constraints on the system’s behavior, such as performance, security, reliability, maintainability, and legal compliance. These are often more critical than individual functional features because failing to meet them can render the entire system unusable.

Feasibility Study

Before development begins, a feasibility study determines whether the proposed system is worth implementing given budget, technical skills, schedule, and alignment with organizational goals. Its inputs include preliminary business needs and a high‑level system description, and its output is a report recommending whether to proceed.

In practice, translating business goals into measurable non‑functional requirements can be challenging, and validating such requirements may be costly, but they are essential for successful system delivery.

Overall, the article outlines the four main activities of requirements engineering—feasibility analysis, requirements capture and analysis, specification, and verification—emphasizing their iterative and interdependent nature.