The summary.
THE WORK IS ENCODING BUSINESS DEFINITIONS
Getting them wrong is invisible until someone acts on a wrong number. Write every definition down, with its exclusions and who agreed it.
Ask how something is currently measured — there is usually an existing figure yours must reconcile against or explain.
A SEMANTIC LAYER ONLY ONE TOOL HONOURS DEFEATS THE PURPOSE
Test that the same metric from two tools returns the same value.
AMBIGUOUS JOIN PATHS LET REPORTING TOOLS CHOOSE A ROUTE YOU DID NOT INTEND
Define joins explicitly, hold measures at a single grain, and expose only tables meant for consumption.
NEVER SUM DISTINCT COUNTS ACROSS GROUPS
They double-count entities appearing in several. And test every aggregate against the detail on each build — divergence destroys trust in both.
STORE THE ORIGINAL AMOUNT, CURRENCY, RATE AND DATE FOR EVERY TRANSACTION
A converted amount alone cannot be checked, corrected or restated.
MODEL SUBSCRIPTION STATE OVER TIME, NOT CURRENT STATE
It is the only way to answer what was active on a given date.
