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Re: UFDTF Metamodeling Document

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Fri, 30 Nov 2007 09:39:48 -0500 (EST)
Message-Id: <20071130.093948.110957750.pfps@research.bell-labs.com>
To: alanruttenberg@gmail.com
Cc: ekendall@sandsoft.com, public-owl-wg@w3.org, cawelty@gmail.com

From: Alan Ruttenberg <alanruttenberg@gmail.com>
Subject: Re: UFDTF Metamodeling Document
Date: Fri, 30 Nov 2007 09:32:46 -0500

> On Nov 30, 2007, at 8:57 AM, Peter F. Patel-Schneider wrote:
> 
> > By the way, it appears to me that the RDF metamodel allows regular
> > (unreified) triples (RDFStatement) to be missing a subject, predicate,
> > or object, which is not allowed in RDF.
> 
> Where is this prohibition stated in RDF?
> 
> -Alan

I'm quite amazed that this question was even asked.  The entire notion
of RDF is built around graphs of triples, which, as triples, have to
have all three elements.

However, since you asked.


>From RDF Concepts:

http://www.w3.org/TR/rdf-concepts/#section-triples

6.1 RDF Triples

An RDF triple contains three components:

    * the subject, which is an RDF URI reference or a blank node
    * the predicate, which is an RDF URI reference
    * the object, which is an RDF URI reference, a literal or a blank
    * node

An RDF triple is conventionally written in the order subject, predicate,
object.

The predicate is also known as the property of the triple.

***********************************

http://www.w3.org/TR/rdf-concepts/#section-rdf-graph

6.2 RDF Graph

An RDF graph is a set of RDF triples.

The set of nodes of an RDF graph is the set of subjects and objects of
triples in the graph.

***********************************


>From RDF Semantics:

http://www.w3.org/TR/rdf-mt/#graphsyntax

0.2 Graph Syntax

Any semantic theory must be attached to a syntax. This semantics is
defined as a mapping on the abstract syntax of RDF described in the RDF
concepts and abstract syntax document [RDF-CONCEPTS]. This document uses
the following terminology defined there: URI reference, literal, plain
literal, typed literal, XML literal, XML value, node, blank node, triple
and RDF graph. 

***********************************

http://www.w3.org/TR/rdf-mt/#graphdefs

0.3 Graph Definitions

An RDF graph, or simply a graph, is a set of RDF triples.

***********************************

peter
Received on Friday, 30 November 2007 14:56:25 GMT

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