Cross-jurisdiction product-legality index
Answers 'is this product legal to ship to this state?' by combining a federal list and many incompatible state lists.
how it works
Three separated data layers (federal authoritative, state directories with no common schema, hand-collected shelf data) normalized so the gap between layers is the product; change detection on the state directories.
App: A complete application.
The code for this one lives in a private repo. This page explains the idea so you can build your own.