An acronym has been coined in this industry to express the "I'll know it when I see it" phenomena: IKIWISI. 1995, Electronic Document Management Systems: A Portable Consultant:
Users also often find it difficult to define what they want in abstract or verbal terms independent of some working system : I'll know it when I see it' (IKIWISI). A prototype provides a means for users to say more precisely what they do or do not want. The general idea, then, is to construct a series of prototypes, to allow prospective users to examine each one, and say what changes they want in the next one. 1991, Towards a Theory of Cognition and Computing, page 175:
One of the fundamental difficulties of creating computer systems is the IKIWISI principle. I find it hard to envisage what it is I want, but I am sure that I'll know it when I see it. This principle describes the behaviour of users, who find it far easier to assess a working model than to review a technical document 1997 Design, Specification and Verification of Interactive Systems ’97: Proceedings of the Eurographics Workshop in Granada, Spain, June 4–6, 1997 (2012 reprint)
customers or users do not always know what they want or what they need. Before the arrival of the microcomputer, for example, very few customers would have been capable of expressing their need for a microcomputer. The needs and segments covered only appear clearly once the product or service is on the market - this is known as the 'ikiwisi' syndrome (I'll know it when I see it). But what are the needs of the customer? 1991, Managing Quality Dynamics, page 26:
Another sort of prototype helps in the situation where you are not even sure what behaviour you want - the ikiwisi' syndrome (I'll know it when I see it). This is the sort of prototype that is built for evaluating user interfaces. Prototyping is therefore experimentation designed to yield information for the development process 1990, Strategies for software engineering: the management of risk and quality:
information overload situations; user differences of opinion on preferred displays or interaction styles; or a number of users saying such things as, "I can't really tell you what I need, but I'll know it when I see it (IKIWISI)." 1989, Software risk management, page 125: