Please enable JavaScript.
Coggle requires JavaScript to display documents.
Requirement Engineering 01, Requirements for Critical Systems - Coggle…
Requirement Engineering 01
Process of establishing services customer requires, constraints under which it operates and is developed.
Requirement descriptions
RFP (Request for proposal)
business document that announces project, describes it, solicits bids from contractors to complete it.
SRS (Software Requirement Specification)
describes what software will do and how is it expected to perform, written analysis of customer requirements.
Types of System Requirements
Functional Requirements
How system should react to particular inputs and how system should behave in particular situations
Describe functionality of the system
Functional User Req. - what the system should do
Describe system services in detail
FR Problems
Requirements not stated precisely.
Requirement may be interpreted differently by user and developer
Complete : Should Include the descriptions of all facilities required
Consistent : No conflicts and contradictions in description.
Non functional Requirements
Constraints on the Services or functions
reliability
Compatibility
Particular IDE, Particular Programming language
More critical than functional req, not met system may be useless
may affect overall system rather than individual components
Classification
Product Requirements: specify how product must behave
reliability
performance
space
Often in Conflicts
level of importance
consequence of change
wider business goals
Organisational Requirements: Due to policies of Organization
External Requirements: due to external factors
Goal : User intention
Verifiable NFR : statement that can objectively be tested. e.g. Bandwidth
Metrices for specifying NFR
Speed
Size
Ease of use
Reliability
Robustness
Portability
Domain Requirements
System's operational domain imposes some requirements
create new FR, constraints on existing, define specific computations
Problems:
Understandability
Implicitness
Requirements for Critical Systems
Failure causes significant impact
Business Critical Systems
Mission Critical Systems
Safety Critical Systems
NFRs for critical Systems
Reliability : runtime behaviour
Availability
Failure rate
Performance: speed of Operating System
Response requirements
Throughput requirements
Timing requirements
Security : unauthorised access is not allowed and ensure integrity of system
Usability : User-interface and end-user interaction
well structured user manuals, error messages, consistent interface
Entry, learning, handling, likeablity