Requirement Engineering

Requirement Engineering

1. Requirements

   • A range from a high-level abstract statement of a service to detailed mathematical functional
     • Serve Dual Function
       • Basis for a bid for a contract - must be open to interpretation
       • Basis for the contract itself - must be defined in detail
     • Types Of Requirement
       • User
         • - In Natural language
         • Diagrams of the services provide
         • operational constraints
         • Written for customer
       • System
         • Documents setting out detailed descriptions of the system's function,services and operational constraints
         • Contract between client and contractor(What should implemented in contract)
   • Functional(What system should not do)
     • Statements of services the system should provide
     • how to react to particular inputs
     • how the system should behave in situations
     • User requirements
       • high-level statements of what the system should do
     • System requirements
       • describe the system services in detail
     • Requirements for the MHC-PMS
       • A User shall be able to search the appointments lists for all clinics
       • The system shall generate each day, for each clinic, a list of patients who are expected to attend appointments that day
       • Each staff member using the system shall be uniquely identified by his or her 8-digit employee number
     • Requirements imprecision
       • Problem arise when requirements are not precisely
       • Ambiguous requirements may be interpreted in different ways by developers and user
     • Requirements completeness and consistency
       • Complete
         • Include descriptions of all facilities required
       • Consistent
         • no conflicts or contradiction
   • Non-Functional
     • Constraints on the services offered by the system
       • Example: timing constraints,constraints on the development process,standards,
     • Apply to the system as a whole rather than individual features
     • System properties and constraints
       • reliability
       • response time and storage requirements
       • system representation
     • Requirements impleementation
       • Affect the overall architecture of a system rather than individual components
       • A single-non-functional such as security requirement,generate a number of related functional requirements that define system services that are required
     • Classifications
       • Product Requirements
         • delivered product ,Eg: execution speed
       • Organisational Requirements
         • consequence of organisational, Eg: process standards used
       • External Requirements
         • Arise from factors which are external to the system and its development process Eg: interoperability
     • Goals vs testable non-functional requirements
       • Goal
         • A general intention of the user such as ease of use
       • Testable non-functional
         • A statement using some measure that can be objectively tested
   • Domain
     • Contraints on the system from the domain of operation

2. Ways of Writing a system requirements specification

   • Natural Language
     • Problems
       • lack of clarity
       • requirements confusion
       • Requirements amalgamation
   • Structured Natural Language
   • Guidelines for Writing
     • standard format
     • Use language in consistent way
     • use test highlighting
     • avoid the use of computer jargon
     • include explaination
   • Form-based specification
   • Tabular specification