R3

R3 / 1c:M

Bank Level enables access to one or many Shaft Level

Shaft Level is accessible in zero or one Bank Level

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A Shaft belongs to a single Bank and all of its Shaft Levels belongs to that same Bank. But only some of those Shaft Levels will be accessible with the rest of them being skipped. The skipped Floors are presumably serviced by a different Bank.

So, for a given Shaft Level it either is or isn’t accessible in the current Bank configuration. Furthermore, all Shaft Levels at the same Floor in the same Bank are either accessible or skipped.

Formalization

Accessible Shaft Level.(Floor, Shaft) -> Shaft Level.(Floor, Shaft)
Accessible Shaft Level.(Bank, Floor) -> Bank Level.(Bank, Floor)

Constraints

1. The Shaft Level must be in a Shaft that services the same Bank as that of the Bank Level, so: Bank == /R3/Shaft Level/R28/Shaft/R1/Bank.Name

2. The Floor is the same for both Bank Level and Shaft Level so this referential attribute is merged into a single value in the association class.