In this paper the category of density is introduced as a parameter for the measurement of the level of semantic contextualization of Knowledge Organization Systems. Based on previous research regarding the detailedness of description on a metadata level the concept of network density and iconicity of a system as an indicator for the accessibility and usability will be considered. Hence this approach takes the iconic dimension of Knowledge Organization Systems (KOS) in addition to their sentential foundation into account. In particular the metadata structure of the cultural heritage database Europeana and its diagrammatic dimension serves as an example. The theoretical foundation of this research is provided by Charles Sanders Peirce’s concepts of signs and his concept of iconicity.