Glossary

What is Schema drift?

Updated September 1, 2026

Schema drift is a data source changing its field names, types, codes, or units without telling the systems downstream. The record still arrives and still looks clean; it just no longer means what the pipeline assumes it means. A renamed column, a lab that switches from mg/dL to mmol/L, or a code set that moves versions all count.

The Data Trust Index catches the break in two places. Quality scores resolution, completeness, missingness, and noise floor, so a field that suddenly empties or changes shape loses points at once. Stability scores test-retest reliability, so a source whose measurements stop agreeing with their own history is marked down before a model ever reads them.

Schema drift is the mechanical cousin of temporal drift: nothing about the record decayed, the container changed underneath it.