Seite - 208 - in The Future of Software Quality Assurance

208 H. van Loenhoud me that this was a requirement, so how could I know that it needed testing? Go to the BA and ask why this has not been specified in the first place.” So, off goes the projectmanager,but still youfeeluncomfortableabout the situation. And although you did not know about this requirement, you still consider the absenceofdefects in thesystemtobeyourresponsibility,nomatter thatyoulearned fromthe“seventestingprinciples”thatsoftwareneverwillbe100%defectfree(see [1]). Whatactuallyhappenedwasthatyouwerestruckbyasubconsciousrequirement: a requirement that everybody, at least at the user’s side, knows about, but that is considered to be so self-evident that no one takes care of telling, capturing,or doc- umenting it. In the remainderof this chapter,we will look intoa bitof theoryabout thesesubconsciousrequirementsandsee if wecanfindways todealwith them. 2 WhatAre SubconsciousRequirements? The concept of subconscious requirements stems from the work of Noriaki Kano, professor at the Tokyo University of Science. In the early 1980s Kano laid the foundation for a new approach to modeling customer satisfaction and developed a customer satisfaction model (now known as the Kano model) that distinguishes between essential and differentiating attributes related to concepts of customer quality [2]. Althoughoriginatingfrommarketingresearch, the Kanomodelhasbecomeone of thefundamentalsofbusinessanalysisandrequirementsengineeringinIT,see for instance[3,4].TheKanomodel(seeFig.1)discerns threecategoriesof factors that are relevant forcustomersatisfaction: • Performancefactors Performance factors relate to features that the customer explicitly asks for. Theyhavealinear relationshipwithcustomersatisfaction: themorethese factors are present in a product or service, the higher the satisfaction. Kano called this “one-dimensional quality,” and in requirements engineering, they are usually referred toas“satisfiers” or“consciousrequirements.” • Basic factors Thesearefactors thatcustomersimplicitlyexpect tobepresent inaproductor service.Thisiswhatrequirementengineeringcalls“subconsciousrequirements,” because customers consider these features self-evident or even are unaware of them.Theyarealsocalled“dissatisfiers”:whensuchfeaturesarepresent,noone willnoticethem,sotheydon’tcontributetothecustomer’ssatisfaction.However, when they are missing, the customer will consider the product or service to be unusableandwill beverydissatisfied. Kanoused the term“must-havequality.” • WOW-factors The thirdcategoryconcernsfeatures, that thecustomersdonotconsider tobe possible,so theywillneveraskfor them.Therefore, theyarecalled“unconscious requirements.” If they are absent in a product or service, the customer will