The size, cost, and complexity of quantitative modeling in the social and physical sciences demand that modelers focus attention on premodeling phases of analysis, specifically on formulation and definition of problems. This is especially true in the areas of futures research and technology assessment. At the problem-defining stage of modeling, a key factor is communication among the modelers who classify and formulate the problems, and a computer-based communication system such as HUB could aid the problem-formulation process. The HUB system facilitates communication in four modes: PLANET conferences, shared visual spaces, program workspaces, and document workspaces. Benefits for users of such a system include: (1) more convenient and frequent communication among geographically distant model builders; (2) an opportunity to explore a greater variety of viewpoints on problems than might ordinarily be expressed due to constraints of time and distance; (3) the use of specific, already-designed techniques for searching out and generating problem definitions; (4) a greater concern for well-written text, concise expression, careful editing, and improved display of information; and (5) a more systematic, clear, and unambiguous articulation of positions that could increase the likelihood of translation, or mutual comprehension, among people looking at problems from different points of view. (AEA)