I got the following question for homework but I am confused on what is being asked. I'm not looking for you to give me the answers I am just wondering what non-functional quantitative requirements are? I thought non-functional requirements, such as as usability, maintainability, etc., were qualitative?

Specify and comment on seven non-functional quantitative requirements for an e-commerce application. You should choose one sub-characteristic from each of the main characteristics [from ISO 9126].

2 Answers 2


Quantative requirements are defined in terms of numerical values.

ISO9126 is a software quality model, which has the following characteristics:

  • Functionality
  • Reliability
  • Usability
  • Efficiency
  • Maintainability
  • Portability

Few examples:


System must be able to handle 10,000 concurrent users.


System must be available in two languages: English and French.

Reference: http://www.sqa.net/iso9126.html

I can't believe they make people pay for this: http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=22749

Wish my homework was that interesting at a time. Good luck.

  • 10000 concurrent users is not scalibility? maybe being able to handle them within a time constraint makes it efficient.
    – jimjim
    Commented Apr 23, 2012 at 23:35
  • Hi, scalability isn't a characteristics of a quality model, therefore I've put the requirement under efficiency. You can rephrase it to say: "System must be able to handle 10,000 concurrent users effectively."
    – CodeWorks
    Commented Apr 24, 2012 at 7:48

Non-functional requirements are defined with numbers. For example, a system cannot be down more than 6 hours in a year. This is a reliability non-functional requirement.

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