Is 1...n the simplified notation of0..1 <--> 0..n

[pstein]

When creating a class diagram then sometimes the designer and authors talk about 1-n relationsships.

On other places the multiplicity is more detailed e.g.

0..1 <---->0..n

Is it the same?

Or does the "1" in an 1-n relation ALWAYS mean ONLY 1..1 and "n" always ONLY an 1...n relation? Mind the exclusion here of the "0"!

Peter

[KP]

In my opinion, the following are all 1-to-many relationships:

Code: [Select]

[1] <---> [1..*]
[1] <---> [0..*]
[0..1] <---> [1..*]
[0..1] <---> [0..*]
The "0" in each case denotes optionality. If you don't want to clutter your model with detail on optionality, choose:

Code: [Select]

   <---> [*]

[Geert Bellekens]

The only "optional" thing is the "0.." in [0..*]
So

Code: [Select]

[*] == [0..*]For the rest, is it as expressed.
So

Code: [Select]

[1] == [1..1] != [0..1]
Geert

PS. I don't think [0..n] is valid UML syntax.

[KP]

Geert, I was talking about meaning not syntax. Example:

Code: [Select]

Vehicle [0..1] <---> [0..*] WheelVehicles may or may not have wheels - wheels are optional. A wheel may or may not be attached to a vehicle - the vehicle is optional.

Your comment on the syntax is correct (at least it would be if YaBB hadn't hidden your '[ * ]'  - it did the same to me   ). I'll just add that [1] is also optional syntax, and can be assumed if no multiplicity is shown.

[Geert Bellekens]

Geert, I was talking about meaning not syntax.

I know, I wasn't trying to contradict you.
Ah, now I see why you could think that, because I also used "optional".

We were absolutely talking about two different "optional"s

Geert

PS. I'll fix the [ * ] thing

[pstein]

The only "optional" thing is the "0.." in [0..*]
So

Code: [Select]

[*] == [0..*]For the rest, is it as expressed.
So

Code: [Select]

[1] == [1..1] != [0..1]Geert

Ok, thank you.
But is this somehow officially defined?

Not that I doubt on your statement, but I need a proof for other colleagues:
Where can I read/verify this?

Is there an (semi-)official,central UML 2.0 syntax reference web page?

Thank you
Peter

[KP]

Not that I doubt on your statement, but I need a proof for other colleagues:
Where can I read/verify this?

Is there an (semi-)official,central UML 2.0 syntax reference web page?

Thank you
Peter

The UML spec can be downloaded free from the OMG website at http://www.uml.org/

Have a look at section 7.3.33 MultiplicityElement. Under "Presentation Options" it says:

If the lower bound is equal to the upper bound, then an alternate notation is to use the string containing just the upper bound. For example, “1” is semantically equivalent to “1..1”.

A multiplicity with zero as the lower bound and an unspecified upper bound may use the alternative notation containing a single star “*” instead of “0..*”.