What Was the Fact?

"Fact tables hold the measurements of an enterprise. The relationship between fact tables and measurements are extremely simple. If a measurement exists, it can be modeled as a fact table row. If a fact table row exists, it is a measurement.

"What is a measurement? A common definition is an amount determined by observation with an instrument or scale."

-- The Data Warehouse ETL Toolkit (2004) Wiley Publishing.

Maybe facts need their own "directed graph" of publicly accessible acknowledgements. And to make it more complex, since we can't write one value to a cell, we may need to record a series of events.