As I described it, Employment is not a role. It could be a moment-interval.
I discussed this issue with Ron Norman, a CCM I'm acquainted with. If you
want to model this differently, you could use roles. Both Coad and Martin
Fowler, in his writings on analysis patterns, suggest the use of roles where
the association has interesting behavior.
Ron said:
I think it might also be modeled as: Company class (green), Person class
(green), and Employee (yellow). Employee would be role played and associated
with Person who is associated with Company. Employee could have same
attributes as you suggest so long as the role is for a single person working
for a single company (roles usually have 0..1 multiplicity between them and
their person/place/thing (green) class.
Bottom line: depends on the domain requirements one is modeling...sometimes
an association class, other times a role. Roles usually only come into play
when their behavior (methods) is interesting and different from other roles
played by the same or different people/place/thing objects.
J.D.
My ideas, my words. You can't blame anyone that might employ me for them.
-----Original Message-----
From: george brown [mailto:[EMAIL PROTECTED]]
Sent: Thursday, December 21, 2000 2:21 PM
To: [EMAIL PROTECTED]; [EMAIL PROTECTED]
Subject: RE: (ROSE) would anyone give me an detailed explaination of
assoc iation
Hi James,
Is the association class of Employment conceptually a "role" played by a
Person in a Company. I.e. what Coad refers to it in "Java Modeling ... using
UML"? I'm not really sure if you've read the book, anyway.
Thanks,
George
>From: "Baker, James D" <[EMAIL PROTECTED]>
>Reply-To: "Baker, James D" <[EMAIL PROTECTED]>
>To: "'[EMAIL PROTECTED]'" <[EMAIL PROTECTED]>
>Subject: RE: (ROSE) would anyone give me an detailed explaination of assoc
>iation
>Date: Thu, 21 Dec 2000 07:30:02 -0800
>
>
>See if this makes any sense to you.
>
>If you have a Person class and a Company class, then one association
>between
>Person and Company might be Employment. Employment has several attributes
>you might want to maintain, such as start date, current salary, vacation
>days accrued, etc. In this case, the association would be modeled as a
>class.
>
>To generalize from this example, association classes are used when you want
>to specify attributes and operations for an association. There is a
>constraint placed on the association class that there can be only one
>instance of the association class for any set of instances of the other two
>classes.
>
>HTH,
>
>J.D. Baker
>My ideas, my words. You can't blame anyone that might employ me for them.
>
>-----Original Message-----
>From: daniel wang [mailto:[EMAIL PROTECTED]]
>Sent: Thursday, December 21, 2000 6:40 PM
>To: [EMAIL PROTECTED]
>Subject: (ROSE) would anyone give me an detailed explaination of
>association
>
>
>hi :
> i don't really understand the association class in uml. when i should
>make use of them?
>best regards
>
>daniel
>
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