WRT RDF doesn't it simply boil down to being based on graphs which,
quoting from Wikipedia, are "mathematical structures used to model
pairwise relations between objects from a certain collection". So, I'm
confused by comments like "N-ary relations work great in a graph model."
which seems completely at odds with the fact that graph relations are
pairwise. (01)
UML has N-ary associations and AssociationClass, so there's at least one
standard from which the semantics community might steal an idea or two. (02)
Cheers,
David (03)
On 11/4/2011 2:57 PM, AzamatAbdoullaev wrote:
> I believe this fundamental issue more belong to the Ontolog Forum.
> Risk to start the n-relations thread...
>
> Azamat
>
> ----- Original Message -----
> From: "David Booth"<david@xxxxxxxxxx>
> To: "glenn mcdonald"<glenn@xxxxxxxxx>
> Cc: "AzamatAbdoullaev"<abdoul@xxxxxxxxxxxxxx>;<semantic-web@xxxxxx>;
> "Frank Manola"<fmanola@xxxxxxx>; "Sampo Syreeni"<decoy@xxxxxx>;
> <alexandre.riazanov@xxxxxxxxx>
> Sent: Friday, November 04, 2011 3:13 PM
> Subject: Standard representations for n-ary relations [was: Re: relational
> data as a bona fide member of the SM]
>
>
>> Plus RDF doesn't have any *standard* way to tag or represent n-ary
>> relations -- we have taken a do-it-yourself attitude[1] -- and thus
>> tools cannot predictably recognize n-ary relations as such.
>>
>> Personally, I think this is something that would be good to address, and
>> there are several simple ways it could be done.
>>
>> 1. http://www.w3.org/TR/swbp-n-aryRelations/
>>
>> David
>>
>> On Fri, 2011-11-04 at 08:49 -0400, glenn mcdonald wrote:
>>> N-ary relations work great in a graph model. The only reason they seem
>>> awkward in the Semantic Web world, in my opinion, is that RDF leads us
>>> to looking at a graph *decomposition* instead of an actual assembled
>>> graph. This effect cascades onto SPARQL and OWL, and thus we end up
>>> with a great forest we're reduced to looking at, and talking about,
>>> one twig at a time.
>>>
>>> glenn
>>>
>>>
>>> On Friday, November 4, 2011, AzamatAbdoullaev<abdoul@xxxxxxxxxxxxxx>
>>> wrote:
>>>> That's a big issue of Relational Ontology, or "N-Relational Ontology
>>> of Things", as discussed 5 years ago:
>>>> http://lists.w3.org/Archives/Public/semantic-web/2006Apr/0047.html.
>>>> And it is not strange that a consistent formal account of
>>> N-Relations has been long missing. Relations are so ubiquitious and
>>> omnipresent that most people take them for granted. In a general
>>> sense, everything is related to everything. We are related to the
>>> world around us, to other people, to our country, to our family and
>>> children and to ourselves. There are ontological, logical, natural,
>>> physical, mechanical, biological, psychological,
>>> emotional, technological, social, cultural, moral, sexual, aesthetic,
>>> and semiotic relations, to name a few. For most people, there is no
>>> particular problem with most of these relations, may be, except
>>> ontological and semiotic (semantic, syntactic and pragmatic)
>>> relations. However, theorists have been perpetually puzzled over
>>> relations, and they have tried to understand them theoretically and
>>> systematically, but consistent, machine-readable models of relations
>>> have proved extraordinarily difficult to construct:
>>>> "What Organizes the World: N-Relational Entities":
>>>
>http://www.igi-global.com/chapter/reality-universal-ontology-knowledge-systems/28313
>>>> What is hardly questionable, to be implemented, the semantic web
>>> indeed requires a unified formal ontology of relations: UFOR.
>>>> Azamat Abdoullaev
>>>>
>>>> ----- Original Message -----
>>>> From: Frank Manola
>>>> To: Alexandre Riazanov
>>>> Cc: Semantic Web List
>>>> Sent: Friday, November 04, 2011 1:23 AM
>>>> Subject: Re: relational data as a bona fide member of the SM
>>>>
>>>> On Nov 3, 2011, at 6:22 PM, Alexandre Riazanov wrote:
>>>>
>>>>
>>>> On Thu, Nov 3, 2011 at 5:20 PM, Frank Manola<fmanola@xxxxxxx>
>>> wrote:
>>>> On Nov 3, 2011, at 3:19 PM, Alexandre Riazanov wrote:
>>>>
>>>> I have been asking this sort of questions for a while and the only
>>> decent answer I know is that
>>>> Description Logics only work with unary and binary predicates
>>> (classes and properties),
>>>> although I believe RDF was initially developed independently from
>>> the DL and OWL work.
>>>> RIF and RuleML seem to be going in the relational direction (see
>>> also the earlier work
>>>
>http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.48.7623&rep=rep1&type=pdf
>>> by Harold Boley), but it is difficult to break the monopoly
>>>> of RDF+OWL.
>>>>
>>>> From my point of view, a major reason for focusing on unary and
>>> binary predicates (the logical forms that underlie RDF triples) is
>>> that it's easier to deal with the problems of integrating
>>> heterogeneous data (a key issue in the semantic web) if the data is in
>>> (or is mapped to being in) that form, as opposed to data in arbitrary
>>> arity relations (for example, with n-aries you need a schema to
>>> interpret any tuples you encounter "in the wild", otherwise you don't
>>> know what the "columns" mean). If you go back to the period before
>>> the "monopoly of RDF+OWL" :-) and look at the work on integrating
>>> heterogeneous relational databases, one of the major approaches to
>>> developing the mappings between the various relational schemas was by
>>> interpreting the various local schemas in terms of unary and binary
>>> relations for just this reason (compound keys had to be dealt with in
>>> this way too, because the same combinations of columns didn't
>>> necessarily constitute the keys in otherwise corresponding relations
>>> in the different local schemas). Mind you, if you're NOT worried
>>> about integrating heterogeneous data, RDF introduces extra pain of its
>>> own (figuring out all those identifiers, for one thing), but if you
>>> ARE worried about integrating heterogenous data, I think you want
>>> those identifiers around.
>>>> I don't quite understand your argument. Indeed, interoperability is
>>> the target. Syntactic interoperability is not a problem as long as you
>>> use the same or convertible syntaxes.
>>>> Semantic interoperability requires shared understanding of the
>>> identifiers being used, which has nothing to do with arity.
>>> Reinterpreting legacy relational schemas is a related, but separate
>>> issue.
>>>> Binary predicates are often handy to represent attributes, but it
>>> does not mean n-ary predicates cannot be helpful in the same (although
>>> I could not recall a real example) and other KR tasks.
>>>> Let me try again, then (although I can't guarantee I'll be any more
>>> understandable this time!). The original question (I thought) was why
>>> there weren't relational approaches applied in Semantic-Web-like
>>> contexts (where, as you say, interoperability is the target). I cited
>>> the integration of heterogeneous relational databases to argue that,
>>> in this case, where relations were already being used by all parties,
>>> and interoperability was the target, those doing the integration found
>>> that using unaries and binaries helped (I agree that shared
>>> understanding of the identifiers is necessarily for semantic
>>> interoperability, but in RDF+OWL, at least the identifiers are
>>> *there*; those putting the data on the Web had to create them). All
>>> that RDF is doing is starting from the unaries and binaries. This is
>>> not an argument that n-ary relations aren't helpful in data modeling.
>>> Nor is it an argument that you can't do semantic integration using
>>> n-ary relations. I simply think it's *easier* to do that integration
>>> with the RDF approach, and I cited an historical example as evidence
>>> that others have found that as well. Now, they/we may have simply
>>> missed the boat, and if so, someone (possibly you) will have to come
>>> along and show us a better way (I'm serious). There have certainly
>>> been attempts to provide more general KRs (allowing n-ary predicates)
>>> for data/knowledge exchange
>> --
>> David Booth, Ph.D.
>> http://dbooth.org/
>>
>> Opinions expressed herein are those of the author and do not necessarily
>> reflect those of his employer.
>>
>>
>
> _________________________________________________________________
> Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/
> Config Subscr: http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/
> Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
> Shared Files: http://ontolog.cim3.net/file/
> Community Wiki: http://ontolog.cim3.net/wiki/
> To join: http://ontolog.cim3.net/cgi-bin/wiki.pl?WikiHomePage#nid1J
>
> (04)
--
Managing Director and Consultant
TopQuadrant Limited. Registered in England No. 05614307
UK +44 7788 561308
US +1 336-283-0606 (05)
_________________________________________________________________
Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/
Config Subscr: http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/
Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
Shared Files: http://ontolog.cim3.net/file/
Community Wiki: http://ontolog.cim3.net/wiki/
To join: http://ontolog.cim3.net/cgi-bin/wiki.pl?WikiHomePage#nid1J (06)
|