CD7Online is the SaaS application of the seventh version of Cartes & Données (C & D), a decisional statistical mapping and geomarketing software edited by Articque. It allows casual users to easily create maps from statistical and geographical data. 25 years of C & D users' feedbacks allowed us to see that the quality of maps is partly based on the users' good knowledge regarding their data and their ability to select relevant analysis and representation tools. To help users better understand their data and realize better maps, we developed a semantic layer on the top of CD7Online, with an interactive visualization tool for browsing user data knowledge extracted from their workspaces. Here we describe the CD7Online application and the visualization prototype that we will present at the demo session.