Chapter 4 Requirements Engineering - Structured Specifications Quiz

Requirements Specification

• Photos are visible to the moderator and the user who uploaded them.
• Requirements specification is the process of writing down user and system requirements in a requirements document.

User and System Requirements

• User requirements must be understandable by end-users and customers without a technical background.
• System requirements are more detailed and may include technical information.
• Requirements may be part of a contract for system development, making it important to be as complete as possible.

Ways of Writing a System Requirements Specification

• Natural language: requirements are written using numbered sentences in natural language, each expressing one requirement.
• Structured language (natural): requirements are written in natural language on a standard form or template, each field providing information about an aspect of the requirement.
• Design description: uses a language like a programming language to specify requirements by defining an operational model of the system (rarely used).
• Graphical notations: graphical models, supplemented by text annotations, are used to define functional requirements for the system (e.g., UML use case and sequence diagrams).
• Mathematical specifications: based on mathematical concepts, such as finite-state machines or sets, but may not be understood by customers.

Requirements and Design

• In principle, requirements state what the system should do, while design describes how it does it.
• In practice, requirements and design are inseparable, with system architecture influencing requirements and design.

Natural Language Specification

• Requirements are written as natural language sentences, supplemented by diagrams and tables.
• Natural language is expressive, intuitive, and universal.

Structured Specifications

• An approach to writing requirements where the freedom of the requirements writer is limited, and requirements are written in a standard way.
• Works well for some types of requirements (e.g., embedded control systems), but may be too rigid for writing business system requirements.

Form-based Specifications

• Definition of the function or entity.
• Description of inputs and where they come from.
• Description of outputs and where they go to.
• Information about the information needed for the computation and other entities used.
• Description of the action to be taken.
• Pre and post conditions (if appropriate).
• The side effects (if any) of the function.

Tabular Specification

• Used to supplement natural language.
• Particularly useful when defining a number of possible alternative courses of action.