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Re: williams-01, proposal to close (20030411)

From: Brian McBride <bwm@hplb.hpl.hp.com>
Date: Fri, 09 May 2003 11:54:14 +0100
Message-Id: <>
To: Graham Klyne <GK@NineByNine.org>, w3c-rdfcore-wg@w3.org

At 14:10 11/04/2003 +0100, Graham Klyne wrote:

>With reference to:
>   http://www.w3.org/2001/sw/RDFCore/20030123-issues/#williams-01

Which is closed an accepted:

did I mess up somewhere?


>I propose that this comment is addressed by revised text at:
>(copied below)
>This revision is to bring the introduction of the RDF graph concept, and 
>its use of URIs, into line with the agreed model [1], as articulated by 
>Pat [2].  The text has been revised from my original proposal in response 
>to discussion on the RDFcore list.  The change in terminology (property -> 
>predicate) means that the GIF image used section 3.1 is revised.
>[1] [[[ref?]]]
>[2] http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2003Feb/0152.html
>I also note that the description of abstract graph syntax in section 6 is 
>already consistent with this model.
>3.1 Graph data model
>The underlying structure of any expression in RDF is a collection of 
>triples, each consisting of a subject, a predicate and an object. A set of 
>such triples is called an RDF graph (defined more formally in section 6). 
>This can be illustrated by a node and directed-arc diagram, in which each 
>triple is represented as a node-arc-node link (hence the term "graph").
>   [image of the RDF triple comprising (subject, predicate, object)]
>Each triple represents a statement of a relationship between the things 
>denoted by the nodes that it links. Each triple has three parts:
>    1. a subject,
>    2. an object, and
>    3. a predicate (also called a property) that denotes a relationship.
>The direction of the arc is significant: it always points toward the object.
>The nodes of an RDF graph are its subjects and objects.
>The assertion of an RDF triple says that some relationship, indicated by 
>the predicate, holds between the things denoted by subject and object of 
>the triple.  The assertion of an RDF graph amounts to asserting all the 
>triples in it, so the meaning of an RDF graph is the conjunction (logical 
>AND) of the statements corresponding to all the triples it contains.  A 
>formal account of the meaning of RDF graphs is given in [RDF-SEMANTICS].
>3.2 URI-based vocabulary
>A node may be a URI with optional fragment identifier (URI reference, or 
>URIref), a literal, or blank (having no separate form of 
>identification).  Properties are URI references. (See [URI], section 4, 
>for a description of URI reference forms, noting that relative URIs are 
>not used in an RDF graph. See also section 6.4.)
>A URI reference or literal used as a node identifies what that node 
>represents.  A URI reference used as a predicate identifies the 
>relationship between the nodes it connects.  A predicate URI reference may 
>also be a node in the graph.
>A blank node is a node that is not a URI reference or a literal.  In the 
>RDF abstract syntax, a blank node is just a unique node that can be used 
>in one or more RDF statements, and has no globally distinguishing identity.
>A convention used by some linear representations of an RDF graph to allow 
>several statements to reference the same unidentified resource is to use a 
>blank node identifier, which is a local identifier that can be 
>distinguished from all URIs and literals. When graphs are merged, their 
>blank nodes must be kept distinct if meaning is to be preserved; this may 
>call for re-allocation of blank node identifiers. Note that such blank 
>node identifiers are not part of the RDF abstract syntax, and the 
>representation of triples containing blank nodes is entirely dependent on 
>the particular concrete syntax used.
>Graham Klyne
>PGP: 0FAA 69FF C083 000B A2E9  A131 01B9 1C7A DBCA CB5E
Received on Friday, 9 May 2003 06:53:35 UTC

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