A Risk-Based, Value-Oriented Approach to Quality Requirements

When quality requirements are elicited from stakeholders, they're often stated qualitatively, such as "the response time must be fast" or "we need a highly available system". However, qualitatively represented requirements are ambiguous and thus difficult to verify. The value-oriented approach to specifying quality requirements uses a range of potential representations chosen on the basis of assessing risk instead of quantifying everything.

Quantification

Quantification means defining metrics that make a requirement measurable (see the “Measuring Quality Requirements” sidebar). For example, we could quantify the requirement “The response time must be fast” as “The response time shall be less than 0.5 seconds in 98 percent of all user input actions.” Work on quantification was pioneered by Barry Boehm¹ and Tom Gilb,² among others. Today, this topic is broadly covered by standards³,⁴ and textbooks.⁵