Designing or Planning? – Cognitive foundations for design aiding A. O. Kazak¸ cı, A. Tsouki`as LAMSADE - CNRS, Universit´ e Paris Dauphine 75775 Paris Cedex 16, France {kazakci,tsoukias}@lamsade.dauphine.fr Abstract This paper considers the cognitive aspects of designing. We compare these aspects to those of the (hierarchical) planning process; a process which is of common interest for Cognitive Psychology (CP) and Artificial Intelligence (AI). We show that both processes can be analyzed using similar key notions and they both have the same essential characteristics. Therefore, we establish a cognitive equivalence between the two processes. We discuss the implications of such an equivalence, emphasizing three main points. First, the equivalence provides a framework in which to join research efforts coming from design research, AI and CP, to the benefit of all the three fields. Second, it offers the possibility to propose a model of the design process based on the Hierarchical Task Networks (HTN) Planning formalism of AI. As discussed in the paper, such a model would have solid theoretical background and can provide sound foundations for design aiding tools. Third, such a model would facilitate, together with the results established in this paper, interactions between design research and Decision Aiding Sciences. Key words: Design process, planning, design cognition, design aiding, decision aiding. 1 Introduction Designing is a complex activity involving different dimensions and can be ex- amined from various perspectives. Accordingly, design research was developed within various research fields: innovation (Le Masson and Weil, 1999), (Chapel, 1997), (Perrin, 2001), project management (Midler, 1993), engineering (Pahl and Beitz, 1984), artificial intelligence (Kannapan and Marshek, 1996), (Gupta et al., 1996), (Gero, 1998), knowledge representation (Coyne et al., 1990), (Gero, 1990), creativity (Gero, 1996), (Logan and Smithers, 1993), etc. These Preprint submitted to Elsevier Science 18 November 2002