# RuleBook: Invariants for Correctness

## User / DB Rules
i) User never manually inserts, deletes, or modifies rows in:
   * `fin_security`
   * `scrape_state`
iii) One logical month = one `scrape_state` row (`source_name = MLI_<year>_<month>` is unique and immutable)

## Website Rules
iv) Website never updates data for a month once that month has passed
v) Website lists instruments in a stable, append-only order within a month
vi) Ticker (`sym_ticker`) uniquely identifies an instrument on the site
vii) Month headers are semantic and human-readable (e.g., `January 2026`, not random IDs)

## Time & Execution Rules
ix) System clock on the user's machine is reasonably correct