Numerous new developments are under way to make visible who is travelling to Europe. Such developments concern technologies used to monitor and control mobility and borders in Europe, to make known presumed invisible phenomena of border crossings. Research on technologies of bordering however have a tendency to focus only on the invisibility of people. Less attention has been given to the invisibility of those same infrastructures that allow the informational management of mobility, migration and border. Yet bringing the infrastructure itself to the foreground is needed, as infrastructure has a major role in how people are not only represented, but enacted. We therefore propose a new method and tool to address the invisibility of digital infrastructures used at the border. Our focus is on the ontologies, the semantic classifications implemented in the information systems deployed for bordering. The method and tool allow us to compare how migrants are enacted by different authorities in different countries, including European authorities, and were assessed against some criteria drawn from the literature on (data) infrastructures.