 In the context of DIKW, data is conceived of as symbols or signs, representing stimuli or signals, that are "of no use until...in a usable (that is, relevant) form".Zeleny characterized this non-usable characteristic of data as "know-nothing".In some cases, data is understood to refer not only to symbols, but also to signals or stimuli referred to by said symbols—what Zins terms "subjective data".