A defined subset of the IFC schema tailored to a specific exchange use case, so software only has to implement the parts of IFC that use case actually needs. The full IFC schema is huge - an MVD narrows it down to exactly what's needed for one workflow, such as "Coordination View" for clash detection or "Quantity Take-off View" for QTO, so software vendors can certify support for a specific, testable subset instead of all of IFC at once. buildingSMART maintains the official MVDs alongside the IFC standard itself.