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From Joerg von Frantzius <joerg.von.frantz...@artnology.com>
Subject Re: Detecting inconsistencies of mapped-by declarations?
Date Fri, 08 May 2009 13:57:13 GMT
Andy Jefferson wrote:
>> Needless to say that supporting this rare corner case would make the
>> implementation much more complex, in particular with respect to
>> bidirectional management.
>> Maybe we could rule out the use of mapped-by in this case?
> -1
> Just because you don't have need for that case is no reason to prohibit it.
> Heck, the JPA crowd were calling Collection<String> as "exotic" and "corner 
> case" some time back. Nice. Also, JDO is for all datastores not just RDBMS, 
> and while you may just use RDBMS, there are many other datastores where this 
> is very reasonable.
> The whole point of persistence specification is to capture requirements and 
> cater for what people want, not to prohibit when something seems difficult.
I only tried to argue from a point of view of what I'd find sane object
modeling. Some say the UML2 is over-complex in trying to cover
everything, but not even the UML2 covers this, nor does e.g. the Eclipse
Modeling Framework.

What you have here is either two associations sharing one end, or a
single association connecting more than two classes (without it being
n-ary). Whichever way you see it, that's not an association anymore, at
least not from an OOA/D perspective.

Sticking to agreed OOA/D concepts certainly does have its merits, be it
the concept of the "association" or that of "genericity" ;)

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