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R28 / M:M-1

Shaft intersects and opens onto many Floor

Floor is intersected and accessed by many Shaft

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A Shaft must intersect and open onto at least two Floors to be useful. The two-ness constraint is ignored here since it is handled by the definition of Bank Levels. If a level cannot be reached by any Shafts, then it is not a Floor as far as the elevator system is concerned (see Floor class description). So, by definition, every Floor can be reached by at least one Shaft. Multiple Shafts may open onto the same Floor.

While one or more Shafts may physically intersect a Floor, that Floor may still be unreachable if none of the enclosing Banks service that Floor as a Bank Level.

Formalization

Shaft Level.Floor -> Floor.Name
Shaft Level.Shaft -> Shaft.ID