Supporting group work in crisis management: visually mediated human-GIS-human dialogue

information is a fundamental component of many crisis management activities. However, current geospatial technologies do not support work by crisis management personnel, most of whom are not technology specialists-a key impediment is that the technologies require the user to team the system's language. In addition, geospatial technologies are not 'collaboration friendly'-they impede rather than facilitate group work. In this paper we address both issues by presenting (1) a theoretical framework for understanding the roles of visual mediation in map-supported human-human dialogues, and (2) a computational approach for enabling such roles in collaborative spatial decision-making contexts. Building upon our initial implementation of a map-mediated collaborative environment, the DAVE_G system [a natural, multimodal, dialogue-enabled interface to geographical information systems (GIS)], we model human - GIS and human - GIS - human dialogues as complex visual-cognitive signification processes in which maps become dynamic facilitators. Using a scenario simulating two crisis managers dealing with a major nuclear release event, we demonstrate how visual display (in DAVE_G) actively mediates human-human dialogue directed to situation assessment and action planning in real applications.