“…Partial models are a means to formalise information states, representing incomplete world descriptions (e.g., Langen and Treur, 1989); types of world descriptions relevant for design are design object descriptions and requirement sets. To obtain formal semantics of reasoning behaviour in design tasks, a recently developed approach based on partial temporal models is adopted, which has shown to be applicable to different types of (non-monotonic) reasoning (see Engelfriet and Treur, 1994;Gavrila and Treur, 1994;Treur, 1994). Semantics of a reasoning process is formalised by a set of (alternative) reasoning traces, represented by a partial temporal model, i.e., a sequence of partial models.…”