SOFTWARE REQUIREMENTS

Functional Requirements:
* These are statements of services the system should provide
=> how the system should react to particular inputs and
=> how the system should behave in particular situations
* In some cases, the functional requirements may also explicitly state
=> What the system should not do
* The functional requirements definition of a system should be both
=> Complete [i.e. It means that all services required by the user should be
defined]
=> Consistent [i.e. it means that requirements should not have
contradictory definitions]
Non – Functional Requirements:
* These are constraints on the services (Or) functions offered by the system
* They include
=> Timing Constraints
=> Constraint on development process
=> Standards and so on…
* Some non-functional requirements may be process rather than product requirements
* Customer imposes these process requirements for two reasons;
=> System Quality
=> System Maintainability
          non functional requirements are of 3 types they are:-


(i) Product Requirements:
* These requirements results from the need for the delivered product, to behave in a
particular way
Example:
* Requirements on how fast the system must execute and how much memory it requires
* Reliability Requirements [i.e. acceptable failure rate]
* Portability Requirements
(ii) Organizational Requirements:
* These requirements are consequence of organizational policies and procedures
Example:
* Implementation requirements such as programming language (Or) design method used
* Delivery Requirements which specify when the product and its documentation to be
delivered
(iii) External Requirements:
* This requirements arise from factors external to the system and its development process
Example:
* Interoperability Requirements which specify how the system interacts with systems in
other organizations
* Legislative Requirements, which ensure that the system operates within the law