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Re: graphs are sets?! (was: rdfms-difference-between-ID-and-about (was: Issues list update/status?))

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Fri, 5 Oct 2001 13:57:15 -0500
Message-Id: <p05101019b7e3b2b89cec@[205.160.76.189]>
To: Jan Grant <Jan.Grant@bristol.ac.uk>
Cc: w3c-rdfcore-wg@w3.org
>On Fri, 5 Oct 2001, Pat Hayes wrote:
>
>>  >On Thu, 4 Oct 2001, Aaron Swartz wrote:
>>  >
>>  >>  On Thursday, October 4, 2001, at 09:34  AM, Jeremy Carroll wrote:
>>  >>
>>  >>  > I would prefer test1.nt to only have one line if they are
>>  >>  > identical. The
>>  >>  > graph is a set.
>>  >>  > A comment explaining the deletion would then be helpful.
>>  >>
>>  >>  Whoa, whoa, whoa, I don't think we ever agreed to this. It was
>>  >>  my understanding the output was a bag (there wasn't harm in
>>  >>  doing so), but could be interpreted as a set.
>>  >>
>>  >>  When was this changed?
>>  >
>>  >The MT would give the same interpretation for equivalent arcs in a
>>  >multigraph, wouldn't it?
>>
>>  Yes, in fact RDF graphs are multigraphs. However, that means that the
>>  MT works just as well if they are sets or bag. Bags is semantically
>>  harmless and puts a lighter burden in implementers, so I would vote
>>  for bag.
>
>Sets are semantically harmless too and put a lighter burden on me as an
>implementer :-) , so I'd rather do the following:
>
>- treat rdf storage systems as sets (maybe, unless they do something
>groovy with provenance)
>- warn consumers of TripleIterator streams that they may see the same
>statement more than once
>- and so on.
>
>In other words, the behaviour of an application over time as assertions
>and retractions are made is a decision that the application-writer has
>to make and advertise to his users.

Yes, that seems like the most sensible path to take. We should be 
very clear that we officially don't give a damn.

Pat
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Received on Friday, 5 October 2001 14:57:15 EDT

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