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Chapter 12. Beyond Functionality: Softwa... > Defining Quality Attributes

Defining Quality Attributes

Most users won’t know how to answer questions such as “What are your interoperability requirements?” or “How reliable does the software have to be?” On the Chemical Tracking System, the analysts developed several prompting questions based on each attribute that they thought might be significant. For example, to explore integrity they asked, “How important is it to prevent users from viewing orders they didn’t place?” or “Should everyone be able to search the stockroom inventory?” They asked the user representatives to rank each attribute on a scale of 1 (don’t give it another thought) to 5 (critically important). The responses helped the analysts to determine which attributes were most important. Different user classes sometimes had different quality preferences, so the favored user classes got the nod whenever conflicts arose.

The analysts then worked with users to craft specific, measurable, and verifiable requirements for each attribute (Robertson and Robertson 1997). If the quality goals are not verifiable, you can’t tell whether you’ve achieved them. Where appropriate, indicate the scale or units of measure for each attribute and the target, minimum, and maximum values. The notation called Planguage, which is described later in this chapter, helps with this specification. If you can’t quantify all the important quality attributes, at least define their priorities and customer preferences. The IEEE Standard for a Software Quality Metrics Methodology presents an approach for defining software quality requirements in the context of an overall quality metrics framework (IEEE 1992).


  

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