Graphic representations are a thoroughgoing communication language. Their development has received considerable impetus from the field of artificial intelligence and more generally from all those areas which have attempted to "capture" knowledge domains in "digital mode". They are formally represented so that they can be used by specific software engines, e.g. intelligent systems, decision support systems, semantic webs and simulation systems. Thanks to their simplicity and effectiveness, some

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... f these graphic languages have spread beyond the specific area from which they originated, to other areas where their use has often been further simplified and made less rigorous, so that even nonspecialists have been able to capitalise on the basic concepts. The question is: when are these graphic representations useful for the professional communities in fostering horizontal knowledge flow in informal learning processes? This chapter discusses the results of an experimentation with graphic approaches to knowledge representation during informal learning processes based on problem-solving in the healthcare sector. The tools chosen for the experimentation were conceptual mapping and Petri Nets, developed collaboratively online with the aid of the CMapTool and WoPeD graphic applications. 2 Our specific aim was to analyse and discuss their real usability and effectiveness in fostering collaborative interaction, knowledge sharing and information exchange during a process designed to study a specific professional problem.