The first pass is deliberately narrow, and widened only on request. Each pass is reversible, so a filter can be loosened without starting again. A smaller file with known edges is preferred to a larger one without.
Field provenance
Keeping the origin and date of each value with the record instead of flattening it away on delivery.
Change-only refresh
On a repeat build, reporting what actually moved instead of re-delivering the whole file.
Source appraisal
Establishing where each field can come from, how current it is, and what it is permitted to be used for.
Tell us the criteria and we will tell you the count, at no cost either way.