This work applies knowledge engineering’s techniques to medieval illuminations. In this article, an illumination is considered as a graph of knowledge which was used by elites in the Middle Ages to represent themselves as a social group and to exhibit their cultural models and the events in their lives. In order to achieve this, combination of symbolic elements were used to encode influential messages more or less implicitly. Our work aims to identify the meaning of these elements through a logical model using ontologies. The idea is to identify logical reasoning rules and simulate them using artificial intelligence mechanisms. The goal is to facilitate the interpretation of illuminations and provide a logical formalisation of new encoding and information transmission services in the future evolutions of current social media.