Re: question on Class Diagram

Thanks a lot for your answers!

The main point here is that OOA/D relationships are implemented at the
3GL level. Since there are multiple ways to do that one would be
usurping the prerogatives of OOP to specify exactly how the
relationships should be implemented in the OOA/D. IOW, all you define
at the Class Model level is that the relationship exists and what its
controlling characteristics -- multiplicity and conditionality -- are.
(One also defines instantiation and navigation of relationships at the
OOA/D level, but that is done abstractly in dynamic descriptions like
Statechart through abstract action language.)

If I understand correctly what you say, it's not necessary to show in
the class Diagram the
instance field which holds a reference to the other object
(for example the field "flight" in the Segment class). I'll rather
focus on the characteristics of the relationship.

This sounds like you're doing a homework problem rather than modeling
an actual business, so my response will be oriented toward that.

Yes, sorry I forgot to mention, it's a "work" for the University not
for a real business.
I have a simulated interview with a business analyst who gave me this
business model.

I would think that a segment can only happen on one flight, but a
flight could have multiple segments. If I board Flight 123 from Los
Angeles to New York via Chicago, that is one flight but with two
segments: LA to Chicago, and Chicago to NY. If I board that flight from
LA to Chicago, it is the same flight but my itinerary only has one
segment on the flight in that case.

I totally agree with you. This Business Model is really weird. I have
spent weeks searching for an answer on Ariline web sites and all I have
found is that Segment and Flight are just synonyms in the Airline
Industry for the majority of people.

I have inquired at the University to find some clues and I have been
told I have two choices:

1) Implement the BDM as it is. (somehow!)
2) If I plan to change the multiplicity of relations I should explain
exaclty what's the reason for it.

At first I have chosen to follow the indications of the BDM and just
"split" the flight information between Flight and Segment....but as
time passes I think this is really non-sense

In my opinion, the challenge for the student here is to face a problem
(BDM inconsistent) and see how he/she solve this problem.

May I ask you, if you had to model these relationship, what track would
you choose (1 or 2) ?
Thanks a lot in advance......

.

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