This work applies some knowledge engineering techniques to medieval illuminations. In this article we consider an illumination as a graph of knowledge. This graph was used by elites in the Middle Ages to represent themselves as a social group and to represent their lives events. To do this, combinations of symbolic elements are used to encode influence messages more or less implicit. Our work is to identify the meaning of these elements through a logical modeling approach using ontologies. The ultimate idea is to identify logical reasoning rules and to simulate them using artificial intelligence mechanisms, on one hand to facilitate the interpretation of illuminations regard to the context and on the other hand to provide a logical formalization of new encoding and information transmission services in the future evolutions of current social networks.