CODEWITHSUNDEEP
uml
seefin
seefin

Reputation: 23

Using variables in UML multiplicities

I was running a tutorial today, and a we were designing a Class diagram to model a road system. One of the constraints of the system is that any one segment of road has a maximum capacity; once reached, no new vehicles can enter the segment.

When drawing the class diagram, can I use capacity as one of the multiplicities? This way, instead of having 0..* vehicles on a road segment, I can have 0..capacity vehicles.

I had a look at ISO 1905-1 for inspiration, and I thought that what I want is similar to what they've called a 'multiplicity element'. In the standard, it states:

If the Multiplicity is associated with an element whose notation is a text string (such as an attribute, etc.), the multiplicity string will be placed within square brackets ([]) as part of that text string. Figure 9.33 shows two multiplicity strings as part of attribute specifications within a class symbol. -- section 9.12

However, in the examples it gives, they don't seem to employ this feature in the way I expected - they annotate association links rather than replace the multiplicities.

I would rather get a definitive answer for the students in question, rather than make a guess based on the standard, so I ask here: has anyone else faced this issue? How did you overcome it?

Upvotes: 2

Views: 598

Answers (1)

Xaelis
Xaelis

Reputation: 1599

According to the UML specification you can use a ValueSpecification for lower and upper bounds of a multiplicity element. And a ValueSpecification can be an expression. So in theory it must be possible although the correct expression will be more complex. Indeed it mixes design and instance level.

In such a case it is more usual to use a constraint like this:

UML multiplicity constraint http://app.genmymodel.com/engine/xaelis/roads.jpg

Upvotes: 3

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