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Re: Confusion about Collections

From: Frank Manola <fmanola@mitre.org>
Date: Sun, 12 Jan 2003 16:33:08 -0500
Message-ID: <3E21DF14.8020708@mitre.org>
To: Garret Wilson <garret@globalmentor.com>
CC: Shelley Powers <shelleyp@burningbird.net>, www-rdf-comments@w3.org

Garret Wilson wrote:

> Frank,
> Frank Manola wrote:
>> Shelley Powers wrote:
>>> Clarification on this, Frank: there is a strong mapping between the 
>>> of the Container and the generated graph, but almost no mapping at all
>>> between the Collection RDF/XML and the generated graph. One could say 
>>> that
>>> the Collection is the ultimate RDF shortcut. This is going to cause
>>> confusion, particularly as people try and figure how to programmatically
>>> access a 'Collection'. (N-Triples of the graph might help with that.)
>>> Wouldn't be a good idea to show the 'long form' of the Collection, as
>>> tedious as it is, in addition to the short form? With this, then 
>>> people can
>>> see for themselves the mapping. They'll be able to take the steps 
>>> that get
>>> them from Point A to Point B.
>> I need some clarification about your clarification.  I understand what
>> you say about the mapping between the RDF/XML of the collection and the
>> generated graph (there is one;  it's described in the Syntax
>> specification, but reading it isn't for the faint of heart), and I'm
>> concocting some words to try to describe it.  However, I'm not sure I
>> understand what you mean by the "long form" of the Collection.
> Simple: the long form would be, for example (from the primer):
>   <rdf:Description rdf:about="http://example.edu/courses/6.001">
>     <s:students>
>       <rdf:Description>
>         <rdf:type="&rdf;List"/>
>         <rdf:first="http://example.edu/students/Amy"/>
>         <rdf:rest>
>           <rdf:Description>
>             <rdf:type="&rdf;List"/>
>             <rdf:first="http://example.edu/students/Tim"/>
>             <rdf:rest>
>               <rdf:Description>
>                 <rdf:type="&rdf;List"/>
>                 <rdf:first="http://example.edu/students/John"/>
>                 <rdf:rest>
>                   <rdf:Description>
>                     <rdf:type="&rdf;List"/>
>                     <rdf:first="http://example.edu/students/John"/>
>                     <rdf:rest rdf:resource="&rdf;nil"/>
>                   </rdf:Description>
>                 </rdf:rest>
>               </rdf:Description>
>             </rdf:rest>
>           </rdf:Description>
>         </rdf:rest>
>       </rdf:Description>
>      </s:students>
>   </rdf:Description>
> Note that this "long form" doesn't show that each referenced student has 
> an rdf:type of s:student. Maybe the example should just use 
> rdf:Description for each Collection node.


Point of clarification:  none of the forms is supposed to show each 
referenced student as having an rdf:type of s:student.  s:students is 
the name of the relationship between the course and the collection of 
students.  If you wanted to identify the students as each having 
rdf:type of s:student, you could of course do so, but that's not part of 
the example at the moment.

>  > It seems
>> to me that the graph is the "long form" (that is, it shows the consed
>> list, in all its "glory"), and there's a drawn graph in the Primer.  Are
>> you saying that a *triples* version of that graph would be clearer, and
>> would help people more than the drawing (he asked in astonishment)?  If
>> so, do you mean in addition to or instead of the drawing?
> Not the graph, not the triples---the long form of the RDF+XML 
> serialization. (Of course, the graph is very useful, too.)

OK, I now understand what you mean by the "long form";  I just don't 
know how much it clarifies (the "long form" isn't even illustrated in 
the Syntax spec), and I don't think we expect anyone to write the "long 
form" directly (unlike some of the other abbreviated forms).  I'll think 
about adding this, but even if I do, it won't appear in the Last Call 
version (which we expect to be out shortly).


Frank Manola                   The MITRE Corporation
202 Burlington Road, MS A345   Bedford, MA 01730-1420
mailto:fmanola@mitre.org       voice: 781-271-8147   FAX: 781-271-875
Received on Sunday, 12 January 2003 16:14:46 UTC

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