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Re: What *is* RDF?

From: Peter Frederick Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 31 Mar 2011 08:18:01 -0400
Message-ID: <20110331.081801.1789717549694762396.pfps@research.bell-labs.com>
To: <richard@cyganiak.de>
CC: <msporny@digitalbazaar.com>, <public-rdf-wg@w3.org>
From: Richard Cyganiak <richard@cyganiak.de>
Subject: Re: What *is* RDF?
Date: Thu, 31 Mar 2011 02:53:51 -0500

> Hi Peter,
> This is nice. (And, I think, almost totally off-topic, but hey the
> chairs said it's ok to go off on tangents up to the F2F.)
> A few comments/questions inline.
> On 25 Mar 2011, at 22:19, Peter Frederick Patel-Schneider wrote:
>> The predicate (or property) of a triple can only be a blank node.
> !!!
>> Aside from strings with a langauge tag, the identifiers for these
>> are borrowed from XML Schema datatypes, but datatypes can be extended
> at
>> will.  It is best not to use this extension facility, and to restrict
>> oneself to strings with language tags plus the built-in boolean,
>> numeric, string, and date datatypes of XML Schema datatypes.
> What's the reasoning behind the assertion that custom datatypes are best
> avoided?

Interoperability.  Not all RDF implementations may understand the literal.

>> All other parts and uses of the built-in vocabulary are controversial
>> and best avoided.
> I hope you didn't mean to indicate that rdfs:label, rdfs:comment and
> rdfs:isDefinedBy are best avoided?

Hmm.  I'll give you (reluctantly) rdfs:label, but I advise against using
rdfs:comment and rdfs:seeAlso and strongly advise against using

>> There is a full-fledged logic that provides the formal meaning for RDF
>> graphs, specified by the RDF Semantics document.  [...]  For various
>> historical reasons, this document divides the meaning into several
>> sections, but this division can be ignored.  
> What exactly do you mean here? The division into RDF entailment,
> datatype entailment etc?

Yes, and into different groupings, etc.

>> This document also does not define a full set of datatypes.  
> I don't understand what you mean by that. It defines the XSD datatypes
> (by reference to XML Schema). Why is that not a full set of datatypes?

I had forgotten this part of the document.  However, the datatype
section is out of date (if XML Schema 2 ever finishes), so my sentence
stands, I think. 

>> The document is missing a few bits that many users of RDF(S) consider
> to be part of RDF(S), notably a notion of equality.
> Do you mean graph equality? Which other bits are missing?


> Cheers,
> Richard

Received on Thursday, 31 March 2011 12:18:54 UTC

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