Every fact is one row in a data file. The row holds the value, the conditions it applies under, the official page it came from, the code section, the date a person last read that page, and its status and tier. Pages are built from these rows; no rule or price is typed into a page.
We read the ordinance, code or schedule itself where we can reach it, and the city or county guide where we cannot, and say which in the code-section column. We re-check every row on a 90-day cycle; the import flags any row older than that.