The model can have any number of units, a unit can have any number of maintainable components and a maintainable component can have any number of failure modes. But there needs to be at least 1 of each.

Units can only be duplicated and edited. Maintainable components and failure modes can be duplicated, edited and deleted.

ARTIS ensures that the names of the units, maintainable components and failure modes are unique in their respective namespaces.