The specification and customization of clinical document types are tasks that need a strong collaboration between domain experts and IT specialists. However, these collaborators are often faced with difficulties due to different interpretation of domain knowledge. Therefore, an adequate method for sharing domain knowledge about documents is necessary. Even though there are some tools that help to define medical document types, there is a lack of approaches that focus on the understandability of the specification for the domain experts. This paper proposes a modeling approach based on the Clinical Document Architecture to address this gap.