Everyone other than CA personnel signs in to a paper access log on entry to the Level 3 area, on top of the records the access-control system keeps. In particular: each entry captures the person's name and signature, their organisation, the entry and exit date and time, why access was needed and, for a visitor, the initials of the escort; the log is kept inside that Level 3 area.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.