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Capturing the discussion (RE: Subjects as Literals)

From: Sandro Hawke <sandro@w3.org>
Date: Wed, 07 Jul 2010 00:01:46 -0400
To: Michael Schneider <schneid@fzi.de>
Cc: nathan@webr3.org, Linked Data community <public-lod@w3.org>, Semantic Web <semantic-web@w3.org>
Message-ID: <1278475306.10248.217.camel@waldron>
Would anyone be willing to try to capture the results of this thread in
a page or two of consensus (neutral point-of-view) text that would
explain the situation to at least a majority of the folks who've jumped
in here with misunderstandings?

To my reading, you (Michael) and Antoine are expressing that most
clearly, if you'd be willing.

It would be good, I think, to incorporate the ideas and perhaps the
structure used at the workshop:
http://www.w3.org/2001/sw/wiki/RDF_Core_Charter_2010#Literals_as_Subjects

... but probably do it on another wiki page, eg:

http://www.w3.org/2001/sw/wiki/Literals_as_Subjects (which does not yet
exist as I write this).

We could think of this as a FAQ response, where the Questions are
something like:
      Why can't I use Literals in the subject position in RDF?
      When are you going to change this?
      How can I work around this restriction?
and maybe:
      What would anyone want to use literals as subjects?
      What would it mean to use a literal as a predicate?

Hoping someone will feel inspired to tie this up with a nice bow,
    -- Sandro

On Tue, 2010-07-06 at 23:40 +0200, Michael Schneider wrote:
> Nathan wrote:
> 
> >Sent: Tuesday, July 06, 2010 11:02 PM
> >To: Pat Hayes
> >Cc: Toby Inkster; Linked Data community; Semantic Web
> >Subject: Re: Subjects as Literals
> >
> >Pat Hayes wrote:
> >> However, before I lose any more of my SW friends, let me say at once
> >> that I am NOT arguing for this change to RDF.
> >
> >so after hundreds of emails, I have to ask - what (the hell) defines
> >RDF?
> >
> >I've read that 'The RDF Semantics as stated works fine with triples
> >which have any kind of syntactic node in any position in any
> >combination.'
> >
> >Do the 'RDF Semantics' define RDF? or do the serializations?
> 
> Every formal language is essentially defined by a (abstract) syntax and a
> semantics. The syntax defines which well-formed syntactic constructs exist,
> and the semantics gives meaning to these constructs. 
> 
> RDF is defined by the RDF Abstract Syntax, defined in [1], and the RDF
> Semantics, defined in [2]. 
> 
> Serializations of the (abstract) syntax, as RDF/XML [3] or N3 in the case of
> RDF, are concrete formalisms to encode the abstract syntax of a language
> into a stream of characters so a language construct can be technically
> stored and processed. A serialization does not fundamentally contribute to
> the specification of the language, but is of great importance anyway. An
> abstract syntax cannot really be stored or processed, but is more of a
> conceptual/mathematical model.
> 
> >simply - does RDF support literal subjects or not - I've read the
> >aforementioned sentence to read 'RDF Semantics support literal subjects'
> >or should I be reading 'RDF Semantics could support literal subjects' or
> >'does support literal subjects' or?
> 
> The RDF Semantics could, in principle, cope with generalized RDF, but the
> RDF Abstract Syntax does not support literal subjects. Therefore, RDF as a
> whole does not support literal subjects.
> 
> >Just seeking a definitive bit of clarity on 1: what defines RDF, 2: what
> >is *currently* supported in that definition.
> >
> >Preferably a serialization unspecific answer :)
> 
> Indeed. Even if a serialization of RDF would support literals in subjects,
> RDF as a formal language would still not support it. For instance, N3
> supports certain forms of rules, and TriG supports named graphs. But none of
> these syntactic constructs are supported by the RDF Abstract Syntax. So they
> are not supported by RDF. 
> 
> >Best & TIA,
> >
> >Nathan
> 
> Best,
> Michael
> 
> [1] <http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/>
> [2] <http://www.w3.org/TR/2004/REC-rdf-mt-20040210/>
> [3] <http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210/>
> 
> --
> Dipl.-Inform. Michael Schneider
> Research Scientist, Information Process Engineering (IPE)
> Tel  : +49-721-9654-726
> Fax  : +49-721-9654-727
> Email: michael.schneider@fzi.de
> WWW  : http://www.fzi.de/michael.schneider
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> 
> 
> 
Received on Wednesday, 7 July 2010 04:01:55 UTC

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