In the Middle Ages, some illuminations were intended for the elites of society and served as a means of communication for them to extend their social influences and to represent their social environments. They constitute an information system based on symbolic components linked together by semantic and influential relationships whose structure is close to models representing social relationships and networks. Today, understanding these illuminations and extracting their implicit messages, expressed through the combination of metaphorical graphic elements, are a difficult task reserved for experts. To help these latter and address the semantic heterogeneity of illuminations, this article explores the synergy between knowledge representation techniques and the analysis of medieval documents to build a knowledge model describing these medieval paintings. It proposes a formal ontology composed of items describing the explicit and visible knowledge of medieval illuminations and others expressing their implicit messages. The considered illuminations are part of those ordered or linked to the Burgundy duke, Philiphe le Bon
