Non Functional Requirement.
- 2. Where Do Requirements Come From? Stakeholders • Product user group • Project customer • An analyst/requirement engineer • Project leader • Project team members • Upper management • Project testers • Licensing entities • Outside vendors or suppliers • Government entities
- 4. Functional • Describe the behaviors (functions or services) of the system • Support user goals, tasks or activities • F(input, system state) (output, new state) Output, new state Input, initial state
- 5. Non Functional • Non functional requirement – in software system engineering is, a software requirement that describes not what the software will do, but how the software will do it, for example, software performance requirements, software external interface requirements, design constraints, and software quality attributes. Nonfunctional requirements are difficult to test; therefore, they are usually evaluated subjectively.”
- 6. Cont. • Involves • ilities: understandability, usability, modifiability, reliability, portability, dependability, flexibility, availability, maintainability, scalability etc. • ities: security, safety etc. • ness: user-friendliness, robustness, timeliness, responsiveness, correctness, completeness, conciseness etc. • Others like: convenience, comfort, performance, efficiency, accuracy, consistency, cost, development time, time-to-market etc.
- 7. Non Functional vs. Functional FR Verbs Mandatory Captured in use case Product feature Easy to capture NFR Attributes Not mandatory Captured in quality attribute scenario Product properties Difficult to capure
- 8. Furps +
- 10. Boehm’s NFR list
- 12. Continuing with FURPS + model
- 13. Usability How easy is it for the user to accomplish a desired task? • Learning system features • Using system effectively • Minimizing impact of errors • Adapting to user needs • Increasing confidence • Performing the tasks quickly • Re-establishing the proficiency while using a system after a long time.
- 14. General Scenario • Source – User • Stimulus – What the user wants to do • Artifact – System • Environment – Runtime or configuration time (compiled at deployment time ) • Response – What the system does • Response Measure – time, tries, number of errors or solutions,
- 15. Cont. • Measureable criteria: Time taken to learn how to use. • Realization of the metrics: Minutes taken for some user’s task
- 16. Reliability • Reliability measures the level of risk and the likelihood of potential application failures. • It is the probability that software will work without failure for a specified period of time in a specified environment. • Technically reliability is the ability of a system to behave consistently in the user-acceptable environment. • Reliability is based on the probability that a system will break i.e., the more likely it is to break, the less reliable it is
- 17. Reliability measures • Reliability of software is measured in terms of Mean Time Between Failure (MTBF). For eg if MTBF = 10000 hours for an average software, then it should not fail for 10000 hours of continuous operation. • Failure Rate (λ), which is defined as: number of failures / total time in service. • Realization of metrics: Run it and count no. of crashes per hour.
- 18. Cont. Reliability is measured to find • The performance of software • Life of the software • Cause of failure • No. of failures occurring in a particular time of a software. • Reliability is considered important because it eliminates the failure mode of the software.
- 19. PERFORMANCE
- 20. USER’S CONCERN • Proper resource utilization • Efficiency • Security • Ease-of-use
- 21. EXAMPLE
- 22. TYPES OF PERFORMANCE REQUIREMENTS: A.Response Requirements B. Throughput Requirements C. Availability requirements
- 23. FACTORS AFFECTING PERFOMANCE: • CPU speed • Type of graphics card • RAM size • The number of applications running.
- 24. HOW TO INCREASE PERFORMANCE: Performance of a computer can be increased by proper care of hardware maintenance.
- 25. SUPPORTABILITY
- 26. CONCERN • Adaptability • Maintainability • Internationalization • Portability • Tailorability • Replaceability
- 27. ADAPTABILITY To adapt the changes after deployment efficiently
- 28. MAINTAINABILITY: To deal with new technology or to fix the defects
- 29. INTERNATIONALIZATION: Ability to deal with deal with international conventions
- 30. PORTABILITY Can easily be transferred from one environment to another
- 31. TAILORABILITY: Changing aspects of an application’s functionality
- 32. REPLACEABILITY: Replacing another system that performs the same functionality
- 35. 1.Implementation requirements: Examples: • Direct changing. • Parallel running of coding. • Third party component involving. • Implementation languages. • Platform support. • Limited resources. • Required standards • Rights for database integrity. • Operation environments. Operation environments. Implementation languages. Required standards Parallel running of coding. Direct changing.
- 37. 3. Physical requirements: A physical requirement specifies a physical constraint imposed on the hardwaresuse for a software. Example: • Material • Shape • Size • Weight
- 38. 4. Packaging requirements: These tools cover every aspect of building, installing and maintaining software packages and include the ability of having multiple versions of a single software package installed concurrently. Example: Windows vista. Windows 7,8 and 8.1.
- 40. 6. Legal requirements. • Piracy Control • Copyright laws • Privacy Laws • Safety Instructions