Non-functional requirements are attributes that either the system or the environment must have. Such requirements are not always in the front of stakeholders' minds, and often you must make a special effort to draw them out.
To make it easier to capture non-functional requirements, we organize them into five categories:
1.Usability
2.Reliability
3.Performance
4.Supportability
5.Security
Usability describes the ease with which the system can be learned or used. A typical usability requirement might state:
•The system should allow novice users to install and operate it with little or no training.
•The end user shall be able to place an order within thirty seconds.
•The end user shall be able to access any page within four seconds.
Reliability describes the degree to which the system must work for users. Specifications for reliability typically refer to availability, mean time between failures, mean time to repair, accuracy, and maximum acceptable bugs. For example:
•The system shall meet the terms of a Service Level Agreement.
•The mean time to failure shall be at least four months.
Performance specifications typically refer to response time, transaction throughput, and capacity. For example:
•All Web pages must download within three seconds during an average load, and five seconds during a peak load.
•While executing a search, the system must be able to display 500 search results per page.
Supportability refers to the software's ability to be easily modified or maintained to accommodate typical usage or change scenarios. For instance, in our help desk example, how easy should it be
to add new applications to the support framework? Here are some examples of supportability requirements:
•The system shall allow users to create new workflows without the need for additional programming.
•The system shall allow the system administrator to create and populate tax tables for the upcoming tax year.
Security refers to the ability to prevent and/or forbid access to the system by unauthorized parties. Some examples of security requirements are:
•User authentication shall be via the corporate Single Signon system.
•Only authorized payroll administrators shall be permitted to access employee pay information.
In Other Words
Nonfunctional requirements refer to elements that are related to the product but don’t describe the product directly.
Also , often Non-Functional requirements are referred to as 'Technical requirements' or 'Performance requirements'.
To make it easier to capture non-functional requirements, we organize them into five categories:
1.Usability
2.Reliability
3.Performance
4.Supportability
5.Security
Usability describes the ease with which the system can be learned or used. A typical usability requirement might state:
•The system should allow novice users to install and operate it with little or no training.
•The end user shall be able to place an order within thirty seconds.
•The end user shall be able to access any page within four seconds.
Reliability describes the degree to which the system must work for users. Specifications for reliability typically refer to availability, mean time between failures, mean time to repair, accuracy, and maximum acceptable bugs. For example:
•The system shall meet the terms of a Service Level Agreement.
•The mean time to failure shall be at least four months.
Performance specifications typically refer to response time, transaction throughput, and capacity. For example:
•All Web pages must download within three seconds during an average load, and five seconds during a peak load.
•While executing a search, the system must be able to display 500 search results per page.
Supportability refers to the software's ability to be easily modified or maintained to accommodate typical usage or change scenarios. For instance, in our help desk example, how easy should it be
to add new applications to the support framework? Here are some examples of supportability requirements:
•The system shall allow users to create new workflows without the need for additional programming.
•The system shall allow the system administrator to create and populate tax tables for the upcoming tax year.
Security refers to the ability to prevent and/or forbid access to the system by unauthorized parties. Some examples of security requirements are:
•User authentication shall be via the corporate Single Signon system.
•Only authorized payroll administrators shall be permitted to access employee pay information.
In Other Words
Nonfunctional requirements refer to elements that are related to the product but don’t describe the product directly.
Also , often Non-Functional requirements are referred to as 'Technical requirements' or 'Performance requirements'.
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