# Re: Dark triples, motivating examples

From: Graham Klyne <GK@ninebynine.org>
Date: Wed, 17 Apr 2002 09:41:30 +0100
Message-Id: <5.1.0.14.2.20020417093420.00a94ec0@joy.songbird.com>
To: "Seth Russell" <seth@robustai.net>
```At 08:09 PM 4/16/02 -0400, Pat Hayes wrote:
>>From: "Pat Hayes" <phayes@ai.uwf.edu>
>>
>>>  >I fail to see how the triple refered to by a reification quad is *not*
>>dark
>>>  >in the graph which contains it.  For example:
>>>  >
>>>  >In a graph containing this reification quad:
>>>  >
>>>  >_:1 rdf:type rdf:Statement.
>>>  >_:1 rdf:subject foo:S.
>>>  >_:1 rdf:predicate foo:V.
>>>  >_:1 rdf:object foo:O.
>>>  >
>>>  >The triple:
>>>  >
>>>  >foo:S foo:V foo:O.
>>>  >
>>>  >Is *certainly* dark.
>>>
>>>  Well, its not even there, so I would say the questions of its
>>>  darkness or lightness don't even arise.
>>
>>Point taken.   I'm just trying to figure out if we can consider the RDF
>>reification quad to be a dark triple relative to the document (graph) in
>>which that quad exists .... or not?  Seems to me that you are stopping short
>>of actually saying that .... why?
>
>Er...because it would be false? Look, a dark triple is supposed to be a
>triple which IS PRESENT in an RDF graph, but for some reason isn't being
>asserted there. So a triple which isn't even in the graph can't be said to
>be 'dark' in any useful sense.

[With apologies to Idries Shah, c.f. The Exploits of the Incomparable Mulla
Nasrudin...]

Someone saw Nasrudin searching for something on the ground.
'What have you lost, Mulla?' he asked.  'My triple', said the Mulla.  So
they both went down on their knees and looked for it.
After a time the other man asked: 'where exactly did you drop it?'