R4

R4 / 1:1

Door is passenger entry for exactly one Cabin

Cabin passengers enter via exactly one Door

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Every Cabin is built with one Door. Cabins with more than one opening (front and back) are not considered in this release. A Door is built into exactly one Cabin.

Regarding inner vs. outer doors, see the Door class description.

Formalization

Door.Shaft -> Cabin.Shaft