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From Craig L Russell <Craig.Russ...@Sun.COM>
Subject Re: Dependent and element-dependent
Date Sat, 12 Nov 2005 23:54:18 GMT
Hi Jörg,

On Nov 3, 2005, at 1:49 AM, Jörg von Frantzius wrote:

> Hello,
>
> the specification currently is somewhat confusing where it defines  
> the meta-data attributes "dependent" and "element-dependent".  
> Concerning "dependent" it says:
>
>    "The dependent attribute indicates that the field contains a
>    reference that is to be deleted

The reference is the object that is referenced by the field. I'll try  
to clarify this in the spec.

>    from the datastore if the referring instance in which the field is
>    declared is deleted, or if the
>    referring field is nullified."
>
> Now does that mean that really the *reference* is to be deleted  
> (which seems kinda natural to me), or rather the object being  
> referred to? Probably the latter?

Yes.
>
> For collection fields, there is the additional "dependent-element"  
> attribute of the "collection" tag. Wouldn't it be enough to have  
> "dependent" on the field level?

We try to make the field metadata refer to behavior of the field  
itself, and put the behavior of multi-valued field types (array,  
collection, map) in separate metadata to better match the semantics  
of Collection versus Element.

We could make it illegal to specify dependent on field types of  
array, collection, and map...

> Or what does it mean if the user specifies 'dependent="false"' with  
> nested 'element-dependent="true"', or vice-versa?

See above.

Experts, any opinion on this subject?

Craig
>
> Thanks for any explanations,
> Jörg
>
> -- 
> __________________________________________________________
> Dipl.-Inf. Jörg von Frantzius  |            artnology GmbH
>                               |                Milastr. 4
> Tel +49 (0)30 4435 099 26      |              10437 Berlin
> Fax +49 (0)30 4435 099 99      |  http://www.artnology.com
> _______________________________|__________________________
>

Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:Craig.Russell@sun.com
P.S. A good JDO? O, Gasp!


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