W3C home > Mailing lists > Public > public-rdf-wg@w3.org > April 2012

Re: complete vs partial graph semantics

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Thu, 12 Apr 2012 13:22:56 +0100
Message-ID: <4F86C920.6090808@epimorphics.com>
To: public-rdf-wg@w3.org


On 11/04/12 18:40, William Waites wrote:
> On Wed, 11 Apr 2012 10:37:22 -0400, Sandro Hawke<sandro@w3.org>  said:
>
>      sandro>  Put differently, as a test case:
>      sandro>
>      sandro>  Trig Document 1 (D1):<u>  {<a>  <b>  1 }
>      sandro>
>      sandro>  Trig Document 2 (D2):<u>  {<a>  <b>  2 }
>      sandro>
>      sandro>  What is the merge/union of D1 and D2?
>      sandro>
>      sandro>  It's not defined, when asked like this.  We use
>      sandro>  something Trig-Like but different:
>      sandro>
>      sandro>      D1A<u>  {+<a>  <b>  1 } D2A<u>  {+<a>  <b>  2 }
>      sandro>
>      sandro>  in which case the merge is:
>      sandro>
>      sandro>      D3A<u>  {+<a>  <b>  1,2 }
>      sandro>
>      sandro>          ==or==
>      sandro>
>      sandro>      D1B<u>  {=<a>  <b>  1 } D2B<u>  {=<a>  <b>  2 } in
>      sandro>
>      sandro>  which case there is no merge; they are inconsistent.
>
> Reading some of the background discussion, talking about crawler dumps
> and such, it seems to me there is quite a bit more information we
> might want to carry around in the "header" of a trig document.
>
> For example, if D1 was downloaded at time t1 and D2 at t2, one could
> reasonably conclude that even with the + notation it is inappropriate
> to merge them, D2 having superceded D1.
>
> Or perhaps D1 comes from a reliable source and D2 comes from someone
> whose data I'll use if I don't have anything better but otherwise I
> wouldn't trust. So when combining the information I'll throw out the
> second version. But perhaps I would nevertheless keep it around and do
> a straight additive merge if I know the cardinality of<b>  to be
> greater than 1.
>
> My point is that combining data from different sources, or the same
> source at different times, is likely to need to take into account more
> than just the +/= hints. Some of this information can be in-band
> (e.g. time, source) and some must necessarily be out of band (e.g. how
> much I trust that source).
>
> Cheers,
> -w

I wholeheartedly agree.

	Andy
Received on Thursday, 12 April 2012 12:23:35 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 6 January 2015 22:02:04 UTC