W3C home > Mailing lists > Public > semantic-web@w3.org > March 2008

Re: meta-information about assertions

From: cdr <_@whats-your.name>
Date: Tue, 4 Mar 2008 07:33:43 -0500
To: Richard Cyganiak <richard@cyganiak.de>
Cc: Cristiano Longo <cristiano_longo@yahoo.it>, semantic-web@w3.org
Message-ID: <20080304123343.GA16178@m.hsd1.ma.comcast.net>

> Not quite. The idea is that RDF statements never exist just floating around 
> freely; they are always inside some container, a graph or a document. Now 

why do you say they can only exist in the wrapper of a graph or document. why not a statement?

> The main difference is that with reification, we give a URI as a name to 
> each individual RDF statement. Then we can make statements about each 
> individual RDF statement. This is more flexible than the Named Graphs 
> model, but it makes management of statements much more complex.

how so? i find the reverse. graphs are optimized at the implementation level in different ways than something atomic/tiny like a statement or URI. people are advocating a new graph for each statement despite this.. 

i wouldnt mind new graphs all over the place, but nobody answered my question about how it relates to HTTP. theres an implicit 'default' graph and no way to get at any other. theres not even any talk on if you GET a subject URI, whether that should return all statements with that subject in _any_ graph... then theres no real serialization support for either in-graph reification or named graphs anyways..

if your statements have URIs, managing them is not 'much more complex' than graphs. and giving a URI to a statement is trivial. stop the FUD..

>> I noticed that Evaluation and Report Language,
>> Semantic Web Publishing Vocabulary(WIQA) and Ratings
>> Ontology follows this second trend(probably also Proof
>> Markup Language), providing properties to specify the
>> asserter of something(e.g. in EARL an agent assert
>> that a document passed or not a checkpoint).

yay... all sorts of indirection and the OWL clusterf*ck just to provide assertions..


im off to look at stuff where (real-world, distributed,  messy, of-varying-certainty) assertions are first class and the core component designed around from teh beginning.. rather than a hacky afterthought with tons of subpar half-solutions that dont even mesh with the rest of webarch..


>
> Uhm, WIQA is in the first camp, it's based on the Named Graphs model, like 
> SPARQL. Both approaches need properties to specify e.g. the asserter of 
> something with both approaches, that's not a difference. The difference is 
> that the first approach attaches metadata to entire containers of RDF 
> statements, while the second approach attaches metadata to individual RDF 
> statements.
>
> Best,
> Richard
>
>
>>
>>
>> So i think that probably(if not exists), for
>> interoperability purposes, we need to formalize these
>> situations into a main specification(or extending a
>> suitable one), preferably grounding it with
>> description logics.
>>
>> Thank you and sorry for my english,
>> Cristiano Longo
>>
>> --- Chris Bizer <chris@bizer.de> ha scritto:
>>
>>> Hi Cristiano,
>>>
>>> as Steffen already said, using the Named Graph data
>>> model together with
>>> SPARQL is a  practical and well tested way for doing
>>> this.
>>>
>>> Reification is considered dead by most people
>>> working on Semantic Web-based
>>> data integration. I think the only people still
>>> thinking about using
>>> reification are the new OWL working group and I hope
>>> that they will also
>>> realize at some point that they are running into
>>> problems with this.
>>>
>>> If you need a vocabulary for representing
>>> meta-information about graphs, one
>>> option is to use the Semantic Web Publishing
>>> vocabulary. A framework that
>>> might be interesting for you with regards to trust
>>> is the WIQA Web
>>> Information Quality Assessment framework, which
>>> employs the Named Graphs
>>> data model and allows you to formulate various
>>> information filtering
>>> policies using a policy language that is based on
>>> SPARQL.
>>>
>>> See:
>>>
>>> http://www4.wiwiss.fu-berlin.de/bizer/WIQA/index.htm
>>>
>> http://www4.wiwiss.fu-berlin.de/bizer/WIQA/browser/index.htm
>>>
>>> Cheers
>>>
>>> Chris
>>>
>>>
>>> --
>>> Chris Bizer
>>> Freie Universit?t Berlin
>>> +49 30 838 54057
>>> chris@bizer.de
>>> www.bizer.de
>>> ----- Original Message -----
>>> From: "Steffen Staab" <staab@uni-koblenz.de>
>>> To: "Cristiano Longo" <cristiano_longo@yahoo.it>
>>> Cc: <semantic-web@w3.org>
>>> Sent: Tuesday, March 04, 2008 9:13 AM
>>> Subject: Re: meta-information about assertions
>>>
>>>
>>>> Hi,
>>>>
>>>> here is a WWW08 paper about this:
>>>>
>>>
>> http://www.uni-koblenz.de/~staab/Research/Publications/2008/WWW2008-MetaKnowledge.pdf
>>>> and here is its implementation:
>>>>
>>>
>> http://www.uni-koblenz.de/FB4/Institutes/IFI/AGStaab/Research/MetaKnowledge
>>>>
>>>> Cheers,
>>>> Steffen
>>>>
>>>> Cristiano Longo schrieb:
>>>>> Hi all,
>>>>> i'm trying to merge rdf(more specifically OWL)
>>> graphs
>>>>> from different sources using collaborative
>>> filtering
>>>>> and trust related technologies. But my question
>>> is:
>>>>> what is the proper way to encode a "meta
>>> assertion"
>>>>> like "A says X about B", in order to deal with
>>>>> contraddictory assertions?
>>>>>
>>>>> Reification? Using SKOS? Something else?
>>>>>
>>>>> Thank you in advance.
>>>>>
>>>>>
>>>>>      ___________________________________
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>>>>>
>>>>>
>>>>
>>>
>>>
>>
>>
>>
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Received on Tuesday, 4 March 2008 16:41:00 UTC

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