The elicitation of knowledge and its adequate representation is a pivotal point and often a bottleneck in any knowledge management process. This thesis argues for linking knowledge management with situations where knowledge emerges. Particularly, group situations such as discussions are widely known as sources for the construction of knowledge (e.g. comprehension in general, emerging ideas, decisions and arguments). The approach of the thesis is to take advantage of face-to-face group situations as a natural note situation. Natural means that knowledge is mediated via external representations for example as diagrams and tables or simple blackboard notes and sketches. Complicated tasks are often inherently bound to special representations. These representations are essential for solving problems. They serve as external memory and means of visualisation. They enrich the mediation of the communicated subject and influence it both, normatively and instructively. As a consequence they are classified as epistemic forms. The use of representations generally not linked to any computational support gains from digitalization e.g. to avoid media breaks during further documentation and reuse. Up to now there are only few systems that support cooperative working situations beyond technically enabling a communication channel. It lacks for the integration of cooperative technologies into face-to-face situations that enrich the common communication by additional media and provide methodological support. Within this thesis the support of cooperative work situations has been realised as the starting point for knowledge management, providing sustainable documentation, data retrieval, data integration and knowledge networking. The communication media allow for actively supporting communication strategies, feedback, monitoring, etc. To reach these goals, semi-formal visual languages have been investigated: their use and opportunities. Further, two systems have been implemented, DiscBoard and FreeStyler, that demonstrate the benefits of semi-formal visual languages and implement a visual language approach. Semi-formal visual languages are developed and deployed within these systems to provide means for cooperative reflection. The DiscBoard system realises perspectives in the sense of epistemic forms. Relations between different representational structures are defined in order to generate one diagram from another. These mapping mechanisms include both filters and interpretations and are based on a generic discussion model. FreeStyler focuses on the evolutionary development of linked knowledge maps. Objects of the visual language are containers for informal input that can be combined with handwritings. The objects are potentially active and can be used to network knowledge maps on the fly and to refer to other media. These can be retrieved by an integrated search engine whose answer set is represented within an object of the visual language.