PSS tend to outperform other GIS-based tools in terms of the provision of knowledge, communication of knowledge and support in the analysis of knowledge (Vonk & Geertman, 2008). Despite their knowledge-handling capabilities, these technologies by and large have not entered the realm of non-routine, strategic planning tasks. Strategic tasks rely heavily on dynamic processes of communication and knowledge exchange for learning about a spatial system. Supporting these process-related aspects is important when confronted by divergent knowledge and priorities that compel actors to frame issues differently (Matos Castaño, 2016). Instead, PSS tend to focus on the substantive aspects of a planning issue-e.g. easing traffic congestion, prioritizing land uses (Pelzer et al., 2014). Dealing with well-defined, routine problems is more straight forward since these tasks rely on 'expert knowledge [that] is relatively unambiguous but subject to error because of the extensiveness of the "facts" involved' (Batty, 1995, p. 6). Consequently, PSS that have successfully made the transition to practice typically support routine planning tasks (Couclelis, 2005). According to a study by Vonk et al. (2007b), out of 58 analyzed PSS, 55 systems supported problem exploration and the analysis of trends while only one system supported problem formulation tasks. The functionality of the PSS that were evaluated focused considerably more on analyzing and modelling information than on supporting communication and information gathering, two process-related aspects of problem formulation. Such analyses of PSS use have become associated with the task-technology-user fit model (Vonk, 2006; Goodhue & Thompson, 1995). This model provides insight into the influence of method and tool components on both the process and outcome of group work (Geertman, 2013). Present-day research examining the relationships between planning task, planning support and users is centered on understanding the usefulness of these tools. PSS usefulness is determined in part by the fit between the support function of the system and the planning task, or its utility, and in part by the perceived usability of the utility function (Pelzer, 2017). Several studies provide discussions of usefulness, particularly concerning the potential communication and learning benefits of PSS use (see Shrestha, 2018; Pelzer et al., 2016; Pelzer et al., 2014; Goodspeed, 2013a). Communication and learning are two process-related aspects that I have attempted to link in the previous section to the dynamics of divergence and convergence. Communication and learning have been measured at both the group and individual level. Both levels of analysis are important since planning as a communicative activity is grounded both in the collective common sense of the group acting together and in the knowledge and consciousness that autonomous individuals gain through self-reflection (Alexander, 1988 as cited in Klosterman, 1997). While the term usefulness hints at a bias toward the potential benefits of PSS use, P...