Where, after all reasonable steps, the head reasonably believes a requested record is held but cannot be found or does not exist, the requester must be told by affidavit or affirmation giving a full account of the search and all communications with those who searched; this is treated as a refusal, and a record later found must be released unless a refusal ground applies.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.