Re: [Modeling-users] Re: attaching information to a relation

[Mario R. <ma...@ru...>]

On Lundi, ao=FB 4, 2003, at 20:49, Sebastien Bigaret wrote:
> Mario wrote:
>> just wondering how this can be best done... as a simple example,
>> assume a Person and an Address tables. A Person may have
>> more than one address, but each address may be categorized
>> as being "primary", "secondary", "private", "work", or anything
>> a priori unknown, Where does one best stick this information?
>
> I think this is what uml calls a "qualified association".

Thanks for the explanation(s) below...
This would work just fine, if an Address belongs (exclusively)
to any one Person. What I am looking for is a way to reuse
the same Address for different people, but the type of
relation may be different each time. E.g.

Mr. Dough's lives in a Villa, across from the beach (private Address)
Ladi Lean is the housemaid for Mr. Dough (work Address)
Mr. Dough's little sister spends summers at his villa (secondary=20
Address)
...

The most natural thing to me would be to add a "property"
to the association, if that'd be allowed. I guess one would have
to make an addditional association table for this?

mario



> This is how I
> would model this:
>
>   - add a 'category' attribute to entity Address,
>
>   - add to the Person class methods such as:
>
>       ----------------------------------------
>       def getAddresses(self, type=3DNone):
>         """
>         Returns addresses of a given type, or all addresses if type
>         is None or omitted
>         """
>         self.willRead()
>         if type is None:
>           return self._addresses
>         else:
>           return self.editingContext().fetch('Address',
>                                              'type =3D=3D '%s'"%type)
>       ----------------------------------------
>
>   You can also do in-memory filtering w/ a qualifier, after the
>
>       ----------------------------------------
>       from Modeling.Qualifier import KeyValueQualifier
>       from Modeling.Qualifier import QualifierOperatorEqual
>       from Modeling.Qualifier import filteredArrayWithQualifier
>
>       def getAddresses(self, type=3DNone):
>         """
>         Returns addresses of a given type, or all addresses if type
>         is None or omitted
>         """
>         self.willRead()
>         if type is None:
>           return self._addresses
>         else:
>           q=3DKeyValueQualifier('category', QualifierOperatorEqual, =
type)
>           return filteredArrayWithQualifier(self.getAddresses(), q)
>       ----------------------------------------
>
>   (of course, when all the types are known, you can also use
>   inheritance)
>
>         Cheers,
>
> -- S=E9bastien.