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Re: [OEP] The n-ary relations draft is ready for outside review

From: Natasha Noy <noy@stanford.edu>
Date: Fri, 16 Sep 2005 11:46:53 -0700
Message-Id: <C7CABB10-A245-41FE-A78C-C3A9A387FB76@stanford.edu>
Cc: "swbp" <public-swbp-wg@w3.org>
To: "Booth, David (HP Software - Boston)" <dbooth@hp.com>

Thanks, David. That's a good point, actually. Incidentally, we used  
blank nodes for the first two use cases, but not for the Purchase  
example. I've reworded the bullet.

I'll wait with posting an updated version until the comments from  
Guus this weekend.

Natasha



On Sep 15, 2005, at 8:46 AM, Booth, David (HP Software - Boston) wrote:

> Hi Natasha,
>
> I enjoyed the n-ary relations draft[1].  I have only one substantive
> comment.
>
> I think it is important to point out that in some (many?) cases,
> instances used to represent n-ary relations *should* have  
> distinguishing
> names, and that using blank nodes instead is a potential design  
> pitfall.
>
>
> In section "Considerations when introducing a new class for a  
> relation",
> the first bullet points out:
> [[
> In our example, we did not give meaningful names to instances of
> properties or to the classes used to represent instances of n-ary
> relations, but merely label them _:Temperature_Observation_1,
> Purchase_1, etc. In most cases, these individuals do not stand on  
> their
> own but merely function as auxiliaries to group together other  
> objects.
> Hence a distinguishing name serves no purpose.
> ]]
>
> However, I think the Purchase example is an excellent illustration  
> of a
> case where the instance *should* have a distinguishing name, i.e.,  
> each
> purchase should have its own URI so that other documents can refer
> specifically to that purchase instance.  Later, when the buyer and
> seller are discussing the transaction -- for example, if the order
> wasn't received when expected -- then they can easily and  
> unambiguously
> refer to it.  If the instance does not have a distinguishing name,  
> then
> less convenient, direct and efficient means must be used to refer  
> to it.
>
> To summarize, my points are;
>
> 1. In some cases, instances used to represent n-ary relations *should*
> have distinguishing names (URIs) -- not blank nodes.
>
> 2. The Purchase example is a good illustration of such a case.
>
> 3. Using blank nodes in such cases is a potential design pitfall.
>
> Does this make sense, or have a misunderstood something?
>
> Reference
> 1.
> http://smi-web.stanford.edu/people/noy/nAryRelations/n- 
> aryRelations-2nd-
> WD.html
>
> David Booth
>
Received on Friday, 16 September 2005 18:47:08 UTC

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