A rules-based checker (like SOLIDWORKS Design Checker or PTC Creo ModelCHECK) matches your drawing against a predefined list of format conditions — layer names, title block fields, dimension styles. It's deterministic and reliable for format enforcement, but it can't catch engineering intent issues. An AI drawing checker reads the geometry and annotations to flag problems a rules engine would miss: an ambiguous tolerance callout, a wall thickness that will cause tooling problems, or a note that conflicts with the BOM. The two tools are complementary, not interchangeable.