W3C home > Mailing lists > Public > www-rdf-interest@w3.org > September 2000

Re: Some thoughts on the semantics of domain and range

From: Graham Klyne <GK@Dial.pipex.com>
Date: Thu, 14 Sep 2000 23:23:34 +0100
Message-Id: <4.3.2.7.2.20000914230707.00ab9830@pop.dial.pipex.com>
To: "Lee Jonas" <ljonas@acm.org>
Cc: <www-rdf-interest@w3.org>
At 03:02 PM 9/14/00 +0100, Lee Jonas wrote:
> >>In summary:
> >>* objectivity about all RDF statements on the entire Web is going
> >>to be impossible - subjectivity (relative to a 'frame of reference')
> >>is the only recourse, therefore conclude stuff based on your viewpoint.
> >
> >Well, TimBL and others have asserted that the Web should have a
> >common "proof language", even if individual statements are interpreted
> >w.r.t. some "frame of reference"  (context?).
> >
>
>I carefully avoided the term 'context' to avoid confusion with earlier
>posts.  AFAIK context was the term used to describe a mechanism that
>embodies the explicit description of the circumstances in which associated
>RDF statements apply.

I agree -- I was being a bit cryptic there.  I am currently interested in 
trying to use Contexts (per McCarthy/Guha) to address a number of 
"real-world" modelling challenges with RDF.  I was hinting that contexts 
might be used to encapsulate the frame of reference in which statements are 
interpreted.

[...]

>"Frame of reference" is something altogether different.  My meaning of
>"frame of reference" is the statements that you are privy to and accept.  As
>said before, an application's "frame of reference" may be a single document
>(plus schemas referred to), an entire data store (DBMS / KB / etc), or
>anything in-between, depending upon its task.

Which, I think, can be described as a context in the sense previously 
mentioned.

(I'm not trying to equate them, just suggesting contexts as a tool for 
dealing with frames of reference as you describe them.)

[...]

> >If I understand the concept correctly, this "proof language" embodies
> >some set of rules whereby one can determine the validity or otherwise of
> >some chain of reasoning, based on some set of assertions, including
> >assertions about the nature of the logic of the assertions.  So, for
> >example, fuzzy logic reasoning can be described by some "proof language"
> >assertions, and then fuzzy logic reasoning can be validated using the
> >proof language in concert with those assertions.
> >
>
>This proof language might test the consistency of multiple statements, but
>again, within your frame of reference.

My point here is that the frame or reference for the proof language is RDF, 
and possibly some small elements not yet defined (e.g. 
http://www.w3.org/DesignIssues/Toolbox).

> >I think the RDF/RDFS core should focus on features needed for that
> >common proof language, which means being able to draw some useful
> >inferences independent of frame of reference.  Conjunctive semantics
> >_seems_ to be consistent with that goal.
> >
>
>I disagree.  RDF/RDFS core should focus on making statements and defining
>validity constraints of those statements.  Inference based upon those
>statements in my mind is yet another application of RDF, not core to it.
>Our product - Antology(tm) - is an application of RDF that does not care
>about logic or inferencing.

I don't think this debate is going anywhere.  I think we both have a point 
of view that is tenable and workable.  Our perceptions of the purpose of 
RDF lead us to take different positions.  To my mind, the limited inference 
properties of conjunctive domain/range semantics are useful, and make the 
schema system feel more consistent and meaningful.  I would achieve the 
expressive power you seek in different ways.

Ther is, however an issue that, as currently drafted, the RDFS document 
does not describe conjunctive semantics, not withstanding the claimed 
intent of one author.

> >* rdfs:domain is _very_ useful as it currently stands for asserting model
> >validity (albeit based on your current frame of reference).
> >
> >This, I cannot and do not dispute.  Whether it belongs in the core, I
> >question.
> >
>If rdfs:domain is not in the core then how can you infer resource types from
>its predicates anyway?

In this case, I mean the mechanism that describes domains disjunctively not 
being in the core.

#g


------------
Graham Klyne
(GK@ACM.ORG)
Received on Thursday, 14 September 2000 19:26:12 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:51:44 GMT