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After this chapter the student should have acquired the following knowledge and skills: Specifying non-functional requirements, specifying functional requirements, good/bad requirements, specifying non-functional requirements, types of NFRs, classification of NFRs. | Specification Process Lecture-21 Recap 2 Specifying functional requirements Good/bad requirements Specifying non-functional requirements Types of NFRs Classification of NFRs Today’s lecture 3 Specifying non-functional requirements Classification of NFRs (contd.) Examples of product requirements The System service X shall have an availability of 999/1000 or 99%. This is a reliability requirement which means that out of every 1000 requests for this service, 999 must be satisfied. System Y shall process a minimum of 8 transactions per second. This is a performance requirement. The executable code of System Z shall be limited to 512Kbytes. This is a space requirement which specifies the maximum memory size of the system. The request for the user's PIN shall be issued within 5 seconds of the card being entered in the card reader. This is a performance requirement. We can do some brainstorming when specifying the section special requirements in Use case development. Examples of process . | Specification Process Lecture-21 Recap 2 Specifying functional requirements Good/bad requirements Specifying non-functional requirements Types of NFRs Classification of NFRs Today’s lecture 3 Specifying non-functional requirements Classification of NFRs (contd.) Examples of product requirements The System service X shall have an availability of 999/1000 or 99%. This is a reliability requirement which means that out of every 1000 requests for this service, 999 must be satisfied. System Y shall process a minimum of 8 transactions per second. This is a performance requirement. The executable code of System Z shall be limited to 512Kbytes. This is a space requirement which specifies the maximum memory size of the system. The request for the user's PIN shall be issued within 5 seconds of the card being entered in the card reader. This is a performance requirement. We can do some brainstorming when specifying the section special requirements in Use case development. Examples of process requirements The development process to be used must be explicitly defined and must be conformant with ISO 9000 standards The system must be developed using the XYZ suite of CASE tools Management reports setting out the effort expended on each identified system component must be produced every two weeks A disaster recovery plan for the system development must be specified Examples of external requirements Medical data system The organisation’s data protection officer must certify that all data is maintained according to data protection legislation before the system is put into operation. Train protection system The time required to bring the train to a complete halt is computed using the following function: The deceleration of the train shall be taken as: gtrain = gcontrol + ggradient Deriving NFRs NFRs are difficult to express A number of important issues contribute to the problem of expressing non-functional requirements: Certain constraints are related to the design solution that is .
