Functional and Non Functional Requirement and Examples

Functional Requirements:-

                               Functional requirement specify the system services that is provided.

Requirements depend on user of the software and software type.

Functional requirement are describe in such a way that system user understand easily.

Define specific facilities provided by the system.

Functional requirement define product features.

Functional requirement specify the behavior or function of the system.

Functional requirements may be written at different levels of detail.

Functional requirement specifies that the system should do.

Functional requirement characterize by verb.

Specification of functional requirement of the system should be consistent and complete.

Completeness means that all services required by the user should be defined.

Consistency means that requirement should not have contradictory definitions.

Example of functional requirement:-

1.    Display the name

2.    Total size

3.    Available space

4.    Format of a flash drive connected to the USB port

5.    Add customer

6.    Print invoice

7.    Authentication

8.    Authentication level

9.    External interface

10. Certification requirement

11.  Reporting requirement

12.  Administrative function

13.  Transaction correction

14.  Organization rule

15.  Legal requirements

Non functional requirement:-

Constrains on functions that are provided by system are non functional requirement.

Non functional requirement are not directly concerned with specific services delivered to user.

 Non functional requirement specify the operation of the system.

 Non functional requirement define product properties.

 Non functional requirement describe character of the work.

 Non functional requirement characterized by objectives.

 Non functional requirement effect the architecture of the system.

 Non functional requirement define how a system is to be.

 Non functional requirement are tested objectively b/c requirement are defined

 quantitatively.

 Non functional requirement are more critical than functional requirement.

 Non functional requirements conflict with other functional and non functional   

 requirements. Non functional requirement are difficult to separate from functional requirements.

Example of non functional requirement 

1.    Performance

2.    Availability

3.    Audit control

4.    Scalability

5.    Backup

6. Dependency on other parties
7. Deployment
8. Documentation
9. Disaster recovery
10. Quality (e.g. faults discovered, faults delivered, fault removal efficacy)
11. Recovery / recoverability
12. Reliability (e.g. mean time between failures , or availability)
13. Reporting
14. Resilience
15. Resource constraints (processor speed, memory, disk space, network bandwidth, etc.)
16. Response time
17. Reusability
18. Robustness
19. Safety or Factor of safety
20. Interoperability
21. Maintainability
22. Modifiability
23. Network topology
24. Security
25. Software, tools, standards etc. Compatibility
26. Stability
27. Supportability
28. Testability
29. Usability by target user community
30. Fault tolerance (e.g. Operational System Monitoring, Measuring, and Management)
31. Legal and licensing issues
32. Open source
33. Operability
34. Performance / response time (performance engineering)
35. Platform compatibility
36. Price
37. Privacy
38. Capacity, current and forecast
39. Certification
40. Compliance
41. Configuration management
42. Efficiency (resource consumption for given load)
43. Effectiveness (resulting performance in relation to effort)
44. Emotional factors
45. Escrow