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Re: idempotency of triple stores

From: Henry Story <henry.story@bblfish.net>
Date: Thu, 20 Oct 2005 11:15:44 -0700 (PDT)
To: Mailing Lists <list@thirdstation.com>
cc: semantic-web@w3.org
Message-ID: <20051020104850.S69113@bblfish.net>

My guess is that that depends on the ontology you are using, as well as
the way you have set up your triples store.

If dc:title were defined as being owl:functional or owl:inverseFunctional, 
or if some other constraint existed that had the same effect then adding
duplicate triples would create a contradiction. Your store, or the program
for adding the triples to the store, should take the appropriate action.

I don't think that dc:title has this type of restriction set in the 
ontology. So it would not be wrong for the store to add all three.

Good ontologies should in my opinion be monotonic (not sure how 
indempotency and monotonicity [1] are related). That is if you add new
facts your database should remain consistent. This means that one often
needs to model the state of things at a time. So if a Person has a height
one should not have properties such as

[ a foaf:Person;
   :height "1m45";
   foaf:mbox "joe@smith.org";
   ...
]

As Joe may grow and so end up having a different height. It would be
much better to have something like

[ a foaf:Person;
   foaf:mbox "joe@smith.org";
   :timeSlice [ :date "Jan 12 1990";
                   :height "1m45 ];
   :timeSlice [ :date "Jan 12 2000";
                   :height "1m90";
   ...
]


Ontologies such as this will be much easier to deal with as they
should reduce the need to delete facts.

Henry Story


[1] http://en.wikipedia.org/wiki/Monotonic_function

On Thu, 20 Oct 2005, Mailing Lists wrote:
>
> Hi,
>
> If I am dumping data into a triple store and my data ends up having duplicate 
> triples how is a triple store supposed to handle the dupes?
>
> For example, if I try to insert these three triples:
>
> <isbn:0802130208>		<dc:title>		<"A Confederacy of 
> Dunces">
> <isbn:0802130208>		<dc:title>		<"A Confederacy of 
> Dunces">
> <isbn:0802130208>		<dc:title>		<"A Confederacy of 
> Dunces">
>
> Will I end up with three triples or one in the triplestore?
>
> Is there a specification for how a triple store is supposed to treat this 
> situation or does each follow its own rule?
>
> Thanks,
> Mark
Received on Thursday, 20 October 2005 18:15:53 UTC

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