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Re: Scoping bnodes

From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Date: Wed, 12 Dec 2018 14:56:25 +0100
To: David Booth <david@dbooth.org>, Patrick J Hayes <phayes@ihmc.us>
Cc: semantic-web@w3.org
Message-ID: <596c80fb-977d-d54c-0f68-50ce9f9df2fe@emse.fr>
For me, the problem of scope goes beyond blank nodes.

It would be good to be able to say (in a standard way), for instance:

1) within my scope, this graph has to be interpreted with a unique name 
assumption (I know the things in my local system, I do not identify them 
twice)
2) within my scope, this graph has to be interpreted with a closed world 
assumption (I know everything about my things in my local system, if you 
can't conclude a statement is true from my scoped graph, you can 
conclude it is false)
3) within my scope, bnodes are interpreted as constants (so, the graph 
"ex:s  ex:p  _:bn1, _:bn2" is effectively not equivalent to "ex:s ex:p 
_:bn3")
4) within my scope, I abide by the RDFS entailment regime (or OWL 2 RL; 
or OWL RDF-based semantics; or RDF recognising xsd:duration, 
geo:wktLiterals; etc.) - which means I may not agree with other semantic 
restrictions made by other standard regimes
5) within my scope, this specific set of inference rules hold (such as, 
that owl:sameAs is reflective and symmetric, but not necessarily 
transitive) - if you consume my data, you can assume what you want, but 
you've been warned!

and possibly more:

6) within this scope, the triples are assumed to be truthfuly describing 
the world as it was at this specific time point / time intervale
7) within this scope, the triples are not trustworthy (or only trusted 
to a certain degree)
8) within this scope, the graph describes Mr X's opinion
etc.


Any real life application that consumes an open set of data from the Web 
has, in any case, to define its scoping mechanism. There's much research 
work showing that RDF is used all over the web with different 
assumptions: assumptions regarding bnodes, regarding unique names, 
regarding closed world, even regarding the meaning of normative terms 
like rdfs:domain, rdfs:range, owl:sameAs; regarding literals as well. If 
one ever wants to build an application that consumes Web data at large, 
one has to put barriers to the normative semantics of Semantic Web 
standards.  Unfortunately, the standards do not make this explicit, and 
people have to experience the big slap in the face of Web inference 
before working out yet another scoping mechanism (or just give up and do 
GraphQL...).



--AZ


Le 10/12/2018 à 00:43, David Booth a écrit :
> On 12/8/18 2:32 AM, Patrick J Hayes wrote:
>>
>>
>>> On Dec 5, 2018, at 3:41 PM, David Booth <david@dbooth.org> wrote:
>>>
>>> On 12/3/18 4:38 PM, Patrick J Hayes wrote:
>>>>>     Bnodes introduced to encode
>>>>>     structures like n-ary relational assertions, or lists, or some
>>>>>     complicated piece of OWL syntax, should have a very narrow scope
>>>>>     corresponding to the exact boundaries of those structures, and
>>>>>     hence should be ‘invisible’ from outside (which is why it is fine
>>>>>     to make them vanish in a higher-level syntax using [ ] or ( ).)
>>>>>
>>>>>     Ideally, RDF2 should provide for these structures directly, but
>>>>>     maybe we can get the benefit with a relatively tiny step, just by
>>>>>     having a syntax for RDF which has explicit scoping brackets.
>>>
>>> Interesting idea, and I can see it being useful for RDF streams or 
>>> very large RDF datasets -- to enable blank node labels to be safely 
>>> reused without collision -- but I am also curious:
>>>
>>> 1. How would you envision scope names being used?
>>
>> I was thinking of them simply as a lexical trick to allow bnodes to be 
>> ‘bound’ at a particular scope.
> 
> Actually I was wondering about use cases.  What additional use cases do 
> you think scoped bnode would address, other than the two that I 
> mentioned above?
> 
> Thanks,
> David Booth
> 

-- 
Antoine Zimmermann
Institut Henri Fayol
École des Mines de Saint-Étienne
158 cours Fauriel
CS 62362
42023 Saint-Étienne Cedex 2
France
Tél:+33(0)4 77 42 66 03
Fax:+33(0)4 77 42 66 66
http://www.emse.fr/~zimmermann/
Member of team Connected Intelligence, Laboratoire Hubert Curien
Received on Wednesday, 12 December 2018 13:56:49 UTC

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