Types of Specification 3.3.1

This presentation covers Types of specification: Requirements specification Design specification System specification and the differences between them.

Requirements Specification Developed by the systems analyst who has completed the feasibility and analysis stages of the systems life cycle. This specification is used explain what the system is supposed to do and how it will achieve this. It should also explain how the users will interact with the software.

Requirements Specification It should contain: Functional requirements What the users what the system to be able to do. http://en.wikipedia.org/wiki/Functional_requirements Non-functional requirements How the user wants the system to behave. http://en.wikipedia.org/wiki/Non-functional_requirements

Requirements Specification The contents of the requirements specification should also include: The purpose of the system. i.e. what are it’s objectives? Scope of the system. The proposed timescale of the system. End-user defined constraints including: Budget Time hardware and software choices. A contract.

Scope of the System The events outside the system that cause the system to react. The actors outside the system that interact with the system. The information that flows between the system and the actors outside the system. The major functions included in the system. The user population.

Design Specification Created by the system’s designer. The contents of the design specification will be different depending on what type of system is being created. For example, a spreadsheet needs to contain designs for formulas whereas a website needs to contain information about how pages are linked. There might be some similar design aspects to take on board though… Data input forms might need to be designed?

Design Specification The contents should include: The purpose of the system Assumptions, limitations and constraints Inputs and Outputs Documents and screens/interface Error messages Styles Colours, font sizes, house style etc Validation rules

Design Specification The contents should include: Processing requirements/queries Data structures Modelling diagrams DFDs, ERDs, STDs Hardware Software/programming language to be used Test plan

System Specification This specification defines the requirements of the system including: Operational requirements: What operations should the system carry out? Information requirements: What information should be provided to the end-users? Volume requirements: How much processing will the system have to handle.

System Specification General system requirements: This specification defines the requirements of the system including: General system requirements: Degree of data accuracy needed Security issues Need for audit trails The system’s ability to expand if the company needs to grow or handle more data.