∃bearerOf.SealingFunction ⊓ ∃partOf.Valve ⊓ ∃adjacentTo.ValveClosureMember ⊓ ∃bearerOf.SealingSurfaceQuality
A material artifact that bears a sealing function, is part of a valve, is adjacent to the valve closure member, and bears a sealing surface quality — providing the seating surface against which the closure member bears to achieve shut-off.
The differentia captures the valve seat's unique structural role: it is the specific part that provides the seating interface for the closure member. This distinguishes it from other valve components that have different structural roles within the valve assembly. Differentia now names SealingFunction explicitly (ODR-022 §16): the function was changed from FlowControlFunction because both source definitions describe sealing, and the differentia had not been updated to match.