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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 13:57:18 +0100
Message-ID: <5E13A1874524D411A876006008CD059F06C2432A@0-mail-1.hpl.hp.com>
To: "Butler, Mark" <Mark_Butler@hplb.hpl.hp.com>, "'www-rdf-dspace@w3.org'" <www-rdf-dspace@w3.org>

Mark,

"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 a
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
RDF/XML.

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? My
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 although
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?

thanks

Mark
Received on Thursday, 26 June 2003 08:57:50 EDT

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