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Re: Named graphs etc

From: Pat Hayes <phayes@ihmc.us>
Date: Tue, 9 Mar 2004 10:21:45 -0600
Message-Id: <p06001f29bc739bed4663@[10.0.100.76]>
To: Patrick Stickler <patrick.stickler@nokia.com>
Cc: <www-archive@w3.org>, "ext Jeremy Carroll" <jjc@hplb.hpl.hp.com>, <chris@bizer.de>

>On Mar 09, 2004, at 06:47, ext Pat Hayes wrote:
>
>>
>>--DS-5576863329265350185
>>
>>>On Feb 27, 2004, at 03:13, ext Pat Hayes wrote:
>>>
>>>>  We may, though, end up with an infinite recursion. I.e., we have
>>>>  a graph X that is asserted. In order to say that X is asserted,
>>>>  we have to have another graph X' containing a statement that
>>>>  X is asserted. But if X' is also asserted, we have to have another
>>>>  graph X'' with a statement saying that X' is asserted, etc., etc.
>>>>
>>>>Lewis Carroll was there first:
>>>>
>>>>http://www.lewiscarroll.org/achilles.html
>>>>
>>>>
>>>>  ???
>>>>
>>>>
>>>>
>>>>Nah, don't worry about it. Once you assert something, its 
>>>>asserted. You don't need to assert the assertion.
>>>>
>>>
>>>Sorry, Pat. I don't follow you.
>>>
>>>If there is a graph X and a graph Y, and there is a triple in graph Y
>>>that says that graph X is asserted, yet we find no triple saying that
>>>graph Y is asserted, then is graph X actually asserted? If the triple
>>>asserting graph X is not asserted, then how can graph X be asserted?
>>
>>Maybe we are at cross purposes. I'm assuming that publishing a 
>>graph amounts to asserting it. If not, then you are right: there is 
>>no way to get something asserted by just publishing more statements 
>>about it, if publication does not qualify as assertion. You have to 
>>have a plain assertion somewhere to get the process started.
>
>>On the other side of the coin, if publication (or maybe, 
>>publication in some mode or form) amounts to assertion, then 
>>there's no need to add another graph asserting the assertion. 
>>That's what I meant in my response above.
>>
>
>No. I was not presuming that publishing a graph equates to asserting 
>it. Publishing
>a graph is simply that, making it publically available. How it is 
>intended to be used
>or what its overall purpose is, is another matter entirely.
>
>This came up in the long debates about social meaning. TimBL wanted 
>what you are
>suggesting, that if someone publishes a graph, they are accountable for the
>statements made therein, as automatically asserted.
>
>The problem with that, is (a) is publishing an RDF/XML instance the same as
>publishing a graph?

Yes, of course. You cannot publish an abstraction.

>(b) how can one publish a graph as an example, such that
>its purpose has nothing to do with the substance of any statements within it,
>yet use of the graph as an example requires manipulation of triples (not
>other forms of quotation, reification, etc.).

Good question, and we need a way to do that. The standard logicians 
answer would be to introduce some kind of graph-quoting, and what you 
publish in this case is the quotation. It could be as simple as an 
XML property on the RDF header. See below.

>
>The ability to explicitly mark a graph as asserted is, I think, a 
>needed mechanism.

Or, to cancel the default that it is asserted. We need to be able to 
make the distinction, surely.

>
>Publication of a graph, or an RDF/XML instance, should not equate to 
>assertion.

I don't think that follows. And in any case, its too late to try to 
change this now, seems to me.

>
>>Either way, there's no utilility in having a graph X saying that 
>>another graph Y is asserted. Unless X is asserted then it has no 
>>effect on Y ( as you note); and if you can assert X in some way, 
>>the you can do that to Y directly, so X is unnecessary (as I note).
>
>Right. Hence my recent proposal of a special vocabulary having intra-graph
>bound semantics, which can be used to qualify graphs.

That doesn't work. YOu can't get a graph asserted by relating it to 
another graph, unless that graph in turn is asserted somehow. 
Asserting isn't a kind of logical sentence, it's a speech act. It 
stands outside the logical semantics.

>
>>
>>>That said, I'm starting to appreciate some of Chris' arguments about
>>>all statements being asserted, no matter what.
>>>
>>>I still have some questions about how to "bootstrap" trust, such that
>>>it seems there must be some requirement for each graph to contain
>>>statements reflecting its source/authority (a signature perhaps?)
>>>otherwise, how do you anchor your trust in terms of a given graph?
>>
>>There are folk who worry about this in other settings. I gather 
>>there are recognized techniques, eg having a 'super' source which 
>>is trusted by everyone and acts as a kind of World Bank for 
>>certifying trusted signatures. Things like notary publics are 
>>useful as well. But there dos have to be some kind of 
>>infrastructure for anchoring the trust in, you can't just make it 
>>happen by asserting things.
>>
>
>Right. One way or another, you've got to bootstrap your architecture. But
>ideally, that bootstrapping machinery should be as lightweight as possible,
>pushing as much as possible into the scope of the RDF MT.
>
>It also should be as decentralized as possible.

Well, how about this. Publication is assertion: but what gets 
asserted depends on the publication mode, which is set by an optional 
'publishMode' property in the RDF XML element tag. If it isnt set, 
then the graph is asserted by the publication: the default case. If 
the mode="quote" then what is asserted by the publication is simply 
that the graph exists and has the name that it has, ie this 
publication is like saying

here is the graph named "ex:foo" : "......"

without asserting the graph itself. This still allows other people to 
import it if they want to assert it.
The combination of a publication with mode="quote" and then having 
another asserted graph which just imports he first graph is almost 
exactly like publishing the graph plain.

This mechanism is obviously expandable by allowing other values for 
that property, eg maybe someone wants to say publishMode="deny" or 
publishMode="archaic". It even allows for URIs in there pointing to 
hypothetical future ontologies of publication mode types, whatever. 
And it doesn't require any modification to RDF or to OWL, and its 
uniform across media types.

Pat

>
>Patrick
>
>
>>Pat
>>
>>>
>>>Patrick
>>>
>>>>Pat
>>>>

Sounds like the chorus of an Irish pub song. Do you know "Mush mush 
tooraliaddie"?



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Received on Tuesday, 9 March 2004 11:21:54 UTC

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