After all reasonable steps to find a record, where there are reasonable grounds to believe it is held but cannot be found or does not exist, the information officer must notify the requester by affidavit or affirmation giving a full account of the search, including communications with everyone who searched; this counts as a refusal, and if the record is later found access must be given 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.