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Re: RDF "data model" (was comments on syntax draft)

From: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
Date: Thu, 03 Jan 2002 16:46:00 +0000
Message-Id: <5.1.0.14.2.20020103154921.03941020@joy.songbird.com>
To: Frank Manola <fmanola@mitre.org>, Eric Miller <em@w3.org>
Cc: w3c-rdfcore-wg@w3.org
At 09:36 AM 1/3/02 -0500, Eric Miller wrote:
>At 02:13 PM 1/3/2002 +0000, Graham Klyne wrote:
>>At 08:59 AM 1/3/02 -0500, Frank Manola wrote:
>>>I don't know that anything as short as a "paragraph" is going to get the 
>>>job done.
>>
>>I think there are a *few* key ideas and pointers that it *should* be 
>>possible to get over in less than half a page.  I think brevity here is 
>>key to making sure the ideas are not overlooked.
>>
>>>Why don't you have a look at what's in the Primer now (or I could send 
>>>you the revision), and see if it's along the lines of what you had in mind?
>>
>>I'll do that.  I just found what I think is the latest version.
>
>http://www.w3.org/2001/09/rdfprimer/rdf-primer-20011101 is still the 
>latest version that includes contributions from Aaron, Sean Palmer, Danbri 
>and Frank.
>
>Frank's description of the RDF data model can be found in 
>http://www.w3.org/2001/09/rdfprimer/rdf-primer-20011221 but there are 
>problems associated with the markup that have yet to be corrected.


OK, I took a look and didn't see what I had in mind.  So I guess I've 
painted myself into the corner of having to draft something ;-)

Well here goes...

----

RDF Roadmap/Overview/Key Points     [pick something]

RDF is a general purpose language for representing information on the World 
Wide Web, and in particular metadata about WWW resources.  It is 
constructed using the following key ideas:

- a data model, based on a directed graph structure, labelled with 
URI-references and literal strings.  The nodes of a graph correspond to 
described concepts, and the arcs correspond to primitive RDF statements 
about those concepts.  The graph model is specified in [RDFMT] section x.x, 
and explained in [RDFPrimer] section x.x.

- a formal semantics, in the form of a model theory for the RDF graph 
model.  This explains how meaning can be ascribed to a given RDF graph, and 
provides a basis for determining whether or not some transformation on the 
graph structure can be said to preserve meaning.  The RDF model theory is 
defined in [RDFMT].  A full understanding of the model theory is not needed 
to make use of RDF, and [RDFPrimer] provides an informal account of RDF 
meaning.

- a serialization syntax, as rules for encoding an RDF graph in XML.  The 
syntax specifies XML Infoset forms that describe RDF graphs, and defines 
transformations between an XML Infoset and an RDF graph.  (Other XML 
specifications define the transformation between XML Infoset and textual 
documents.)  The RDF syntax is defined in [RDFSyntax], and explained in 
[RDFPrimer] section x.x.  (NOTE:  other RDF graph serialization forms may 
be defined, sharing the same formal semantics, but these are not part of 
the official specification of RDF.)

- a schema language, which uses RDF to describe RDF vocabularies.  An RDF 
vocabulary designates an intended interpretation for some collection of 
URI-references when used as RDF graph labels.  The RDF schema language is 
defined in [RDFSchema] and explained further in [RDFPrimer] sections on 
"RDF modules".

----

So it's not a paragraph, but it (just) fits on a single screen in my email 
client, which is good enough for me.

The goals of this proposed section, which I think could usefully be 
included toward the start of the Primer, Model Theory and Syntax documents, 
are:
- to set out the key underpinning ideas of RDF, without "fogging" them with 
subservient details,
- to help a reader find both formal specification and explanatory material 
for each of the key areas (i.e. all the details that are deliberately 
omitted here), and
- to use language which is primarily descriptive, but which is also used 
consistently with the more formal definitions.

While the topic coverage is deliberately high-level, the language is 
intended to be technical rather than tutorial.  The descriptions given are 
intended to be completely accurate, if not fully complete.  My intended 
audience here is an experienced developer or system designer who is trying 
to come to terms with RDF.  In short, something like what I would have 
liked to find when I was first encountering RDF in my work on CC/PP.

I hope you find this helpful.

#g



------------------------------------------------------------
Graham Klyne                    MIMEsweeper Group
Strategic Research              <http://www.mimesweeper.com>
<Graham.Klyne@MIMEsweeper.com>
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Received on Thursday, 3 January 2002 11:54:51 EST

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