An extract from the formal UML specification:
"A multiplicity is a definition of an inclusive interval of non-negative integers beginning with a lower bound and ending with a (possibly infinite) upper bound."
So, you can only have one continuous segment as a multiplicity.
In your case I would use 0..* on both ends and specify these special restrictions separatelly. You can specify them more or less formally. Some ideas:
- formal way: using preconditions, postconditions and invariants,
eventually in OCL (please google these terms if you like)
- informal
way: using simple textual notes or class/method descriptions.
This logic could be further implemented in a Movie's method like addStars(Star[]), in order to centralize it. There are a lot of correct solutions however.
Maybe you've noticed that I've recommended 0..* instead of 1..*. This is just a suggestion leading to much more flexible solution. Lower bound of 1 is just too restrictive and should be used only when really necessary (Parent-Child might be an example, Child cannot be born with no Parent). Its value 1 on the Star's end would mean that at least 1 Star must be linked to the Movie in the process of its creation! I find it pretty ugly. What if no Stars are created yet in the system?
What if a Movie is created as a wish-list or the lineup is simply unknown in the time of creation? What if the Movie simply does not have any Stars? :)
By leaving both boundaries on 0, you can create Movies and Start independent of each other. You can always link them later, making your system much more flexible and user-friendly.
