[Crm-sig] *** ISSUE *** Revision of scope note for E73 Information Object to specifically include named graphs

martin martin at ics.forth.gr
Tue Jul 29 15:44:04 EEST 2014


Hi Richard,

On 29/7/2014 12:06 ??, Richard Light wrote:
> Martin,
>
> Thank you for this: I now have a much better idea of what you are 
> trying to express.  I can also now see how the AAT is relevant to the 
> discussion: it is precisely a set of propositions with an identity, or 
> (to use SKOS terminology) a Concept Scheme. (However, I can't see the 
> AAT being cited as justification for an assertion or set of 
> assertions, so maybe it's not that pertinent an example.)
>
> However, the AAT as a concept scheme is identified by the URI:
>
> http://vocab.getty.edu/aat/
>
> which yields a web page when invoked normally, and redirects to:
>
> http://vocab.getty.edu/download/rdf?uri=http://vocab.getty.edu/aat/
>
> when RDF is requested in the HTTP Accept header.  Every concept within 
> AAT contains an assertion that it is skos:inScheme AAT.
>
> So, in what way would you create a Named Graph (in your sense) for the 
> AAT?  What URI would you associate with each triple in the concept 
> scheme? 
http://vocab.getty.edu/aat/
> And what practical benefit does this give you, that simply using the 
> URL quoted above doesn't give you?
You can upload the AAT into a triple store and still know this is the 
same AAT...

An example of a "well known" graph will always have that problem - it is 
defined somewhere else.
In the CRM, we do not require examples to be well known. We can create a 
small TRIG file.

The whole point of a Named Graph is distinguishing a bunch of 
propositions within a database (triple store,
graph database...). If the propositions are still on the Getty server, I 
cannot run a transitive closure etc. on its
content.

You can regard the whole LoD space as a big triple store, but you cannot 
run a query against it up to now.
This part of LoD is still a bit in the science fiction area - at least 
from the point of view of industrial application.
Distributed querying still poses theoretical questions and serious 
performance issues. I'd guess some
20 years to become reality, if ever. The "if ever" comes from my 
concerns how you can manage such a space
without controlled provenance of knowledge with all its ramifications.

Best,

Martin
>
> Richard
>
> On 28/07/2014 11:34, martin wrote:
>> Dear Richard,
>>
>> On 28/7/2014 11:41 ??, Richard Light wrote:
>>> Martin,
>>>
>>> I thought that a major merit of the CRM was that it was an abstract 
>>> model, which could be instantiated using whatever technology was 
>>> felt to be appropriate.  That being the case, I would be concerned 
>>> if RDF-specific techniques were presented to the world as the only 
>>> way in which a particular challenge ("implementing argumentation 
>>> systems ...") could be tackled using the CRM.  Or are you talking 
>>> specifically about RDF implementations of the CRM?
>> I share your concerns :-) !
>>>
>>> Why can't "premises and conclusions" be modelled using reification, 
>>> so they can then be given a unique URI? This is the sort of approach 
>>> which the BM has successfully deployed, as I understand it.  I would 
>>> be grateful if someone could provide a really simple concrete 
>>> example which shows the need for the named graph approach.
>> Your are right!
>>
>> Actually I see the "Named Graph" not as a particular RDF feature, but 
>> at the level of abstraction that Simon pointed
>> out: A set of propositions with a "historical" identity which is not 
>> reduced to the identity of the set itself.
>>
>> The CRM uses an abstract data model of classes, superclasses, 
>> properties, superproperties etc., which is more or
>> less the stable core of all data structures and KR models used so far 
>> in industrial systems. We have however adopted
>> the term "property" from RDF, just to reduce the semantic gap for 
>> people now. Originally, we used TELOS terms, but KIF, OIL was equally 
>> compatible.
>>
>> The requirement to introduce argumentation structures into consistent 
>> graphs of propositions is relatively new.
>> Reification is an atomic mechanism, which does not allow for 
>> describing that a set of propositions is believed
>> together. Therefore it looses an important part of the semantics of 
>> argumentation. A Named Graph is in my mind
>> an abstarction which subsumes reification. Reification is a 
>> workaround using a syntax which has not foreseen the problem before. 
>> Named Graph is a NEW logical construct not found in any other 
>> industrial KR model, and born out of a necessity that first showed up 
>> when integrating different sources. (Before, one could say AI just 
>> slept in a one-truth cyberworld with a god-like user or math on top 
>> of reality).
>>
>> I believe we need the Named Graph construct as a logical form, not as 
>> an RDF syntax, if we want to integrate
>> provenance of knowledge with the CRM. So far, we have evidence of two 
>> real-life data structures, one is
>> archaeological excavation records, and another description of 
>> medieval book-bindings, which systematically
>> register source of evidence and concluded facts. E.g., geometric 
>> topology of stratigarphic units and microsopic
>> stratigraphic interface properties are used to justify chronological 
>> sequence. In a simple model, this is atomic,
>> in a more general, it is probabilistic Bayesian. So, we would need a 
>> "Typed Named Graph", which restricts the
>> propositions in the Graph to a certain schema (topology, chronology), 
>> and then a relationship "is evidence for"
>> between the typed named graphs. The assertion itself forms part of 
>> the belief implicit in the archaeological
>> record.
>>
>> If there is any logician on this mailing list, a proper formulation 
>> of such a construct and an abstract syntax for the CRM would be great 
>> to have!!!
>>
>> We will try to suggest a graphic primitive, which is a bubble around 
>> the propositions with a "hot spot" on the
>> perimeter.
>>
>> Suggestions most welcome!
>>>
>>> To pick up on the suggestion of using the AAT as an example: in what 
>>> way is the AAT a named graph?  Surely it's a SKOS Concept Scheme 
>>> (plus)?  I think it would be impossible to give an example of a 
>>> "well-known" named graph, for the reasons Simon has been explaining.
>> Named Graphs are new, so none is really "well known", but I would 
>> regard a skosified AAT as a Named Graph,
>> as well as all the RDF junks for LoD, once RDF regards any RDF file 
>> as a Named Graph. The only condition is, that
>> two RDF Files with the same content and different URI are not 
>> regarded as being identical (owl:same_as).
>>
>> Best,
>>
>> Martin
>
> -- 
> *Richard Light*
>
>
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