Sets the value of ImplicitOuter. ImplicitOuter is a flag that should be true if IfcCurveBoundedSurface is an implicit boundary of the bounded surface, e.g. the u1, u2, v1, v2 of IfcRectangularTrimmedSurface. If IfcCurveBoundedSurface is a closed composite curve on surface for the definition of an outer boundary, this parameter is false.