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RE: Provenance for section 3 in technologies.tex

From: Seaborne, Andy <Andy_Seaborne@hplb.hpl.hp.com>
Date: Thu, 26 Jun 2003 17:48:15 +0100
Message-ID: <5E13A1874524D411A876006008CD059F06C24340@0-mail-1.hpl.hp.com>
To: "'www-rdf-dspace@w3.org'" <www-rdf-dspace@w3.org>


Jena2 supports both statement and stating reifications.

> statements which are identityless

statements and statings can have identities.


-----Original Message-----
From: Kevin Smathers [mailto:kevin.smathers@hp.com] 
Sent: 26 June 2003 17:21
To: Seaborne, Andy
Cc: Butler, Mark; 'www-rdf-dspace@w3.org'
Subject: Re: Provenance for section 3 in technologies.tex

I thought that Jena 2 was supposed to support the reification of 
statings; on the face of it, it seems silly to support the 
identification of statements which are identityless in their 
abstraction, but not support identification of instances of statements 
which clearly have identity.

That aside, in the case of Simile I think we should definitely be 
talking about statings, not statements.  In its use as a recording 
format for system history we can expect to find many, many copies of 
identical triples whose only distinction is how they are referred to 
from other triples.  Collapsing these into a single instance by using 
statements instead of statings would be to lose all of the information 
that was recorded in those links.  Likewise, in Genesis statings are 
more relevant than statements because of the multi-user nature of 
Genesis -- access controls, ownership, and the like must be tied to 
instances of a subgraph, not to an abstraction of their content.


Seaborne, Andy wrote:

>"Quads" is a term used for several different things.
>>So although
>>they are non-standard at the moment, people are using them, so should we
>>really rule them out?
>Jena could be said to use quads to store reifications.  A statement is
>stored with an "is reified flag" and it optimizes some uses of reification
>(particualrly statement, not stating, usage).  We have users who have large
>datasets who use this internal compression with database-stored statements.
>It is invisible at the API.  
>There are operations directed at helping working with reification - these
>are independent of the storage optimization.  We have had both
>reification-optimizing and non-optimizing store for the same API.
>The RDF/XML generated is as per the working group.
>They are not the same quads as used by RDFStore where the 4th component is
>URI, and indicates the source of the statement.  This is visible at their
>API (and in their version of RDQL) and can not be encoded directly in
>The formulae in cwm/N3 are another approach again.  These are quoted graphs
>at the nodes of the containing graph (i.e. a new node type).
>Using non-standard features precludes interoperability.
>We need a concrete use case for provenance across systems (not just for
>managing data within SIMILE).
>	Andy
>-----Original Message-----
>From: Butler, Mark [mailto:Mark_Butler@hplb.hpl.hp.com] 
>Sent: 26 June 2003 13:12
>To: www-rdf-dspace@w3.org
>Subject: RE: Provenance for section 3 in technologies.tex
>Hi Dave
>>Non-standard extensions would be best avoided if you want 
>>SIMILE to be a full
>>participant in the semantic web.
>But to take this back to my original suggestion does this apply to quads?
>understanding from Andy is that they are used by RDFStore and a number of
>RSS processors, and from Jeremy that although Jena 2 does not have a quads
>API it does actually use a quad data structure "under the hood". So
>they are non-standard at the moment, people are using them, so should we
>really rule them out?
>I'd be interested in feedback here from Eric Miller and David Karger also?

   Kevin Smathers                kevin.smathers@hp.com    
   Hewlett-Packard               kevin@ank.com            
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Received on Thursday, 26 June 2003 12:49:48 UTC

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