This research deals with the development of a tool to enable designers, decision-makers and citizens to jointly shape the physical environments they inhabit, through interaction and communication via electronic networks. The designing of physical environment becomes the collective responsibility of all interested societal actors, who together form a "designing system". This research defines a 'designing system' as a temporary alliance of people responsible for decisions about the spatial development of an area, consisting of public and private investors, and citizens. This research involved the integration of theoretical knowledge, empirical knowledge and information communication technologies (ICT) in order to develop a tool, the decision support system called "Delta M."