SYSML21 — Interface::participants should not be ownedPorts

In the Systems Library model Interfaces, the Interface::participant feature is declared as a port usage. However, the semantic constraint checkPortUsageOwnedPortSpecialization then requires that the feature subset ownedPorts. But ownedPorts is unique, will participant has to be non-unique, which violates the constraint validateSubsettingUniquenessConformance.

The feature Interface::participant should thus not subset ownedPorts. Indeed, an Interface is supposed to be a Connection between the ownedPorts of other parts, so its participants shouldn't be considered ownedPorts of the Interface itself, anyway.