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From: Graham Klyne <GK@ninebynine.org>
Date: Tue, 04 Nov 2003 10:37:09 +0000
Message-Id: <>
To: Adam Souzis <adam-l@souzis.com>, www-rdf-interest@w3.org

At 00:33 03/11/03 -0800, Adam Souzis wrote:
>Rx4RDF provides a deterministic mapping between the RDF abstract syntax to 
>the XPath data model,  allowing you to query, transform and update a RDF 
>model with languages syntactically indentical to XPath, XSLT and XUpdate 
>(which we call  RxPath <http://rx4rdf.liminalzone.org/RxPath>, RxSLT 
><http://rx4rdf.liminalzone.org/RxSLT>, and RxUpdate 
><http://rx4rdf.liminalzone.org/RxUpdate>, respectively).
>A reference implementation (in Python) and formal specification can be 
>found at http://rx4rdf.liminalzone.org/

I'm taking a quick look at the RxPath spec [1], and have a question:

[1] http://rx4rdf.liminalzone.org/RxPathSpec

Do you really mean the Subject Elements to include all graph nodes that 
appear as objects of any statement?  The spec says so, but the naming seems 
at odds with this.

Some other comments:

I'm a little concerned by (what seems to me) the indecisive treatment of 
loops in an RDF graph.  I think having a distinction between 
"circularity-checked" and "circularity-unchecked" *in the data model* is 
confusing.  My inclination would be to let the data model contain infinite 
trees (ala "circularity-unchecked"), and provide for a finite traversal of 
the nodes as an *operational mode* of an RxPath processor.  In practical 
terms, this shouldn't be very different from what I imagine you do now, but 
it feels more soundly based to me.


At first glance, I like your XML serialization for RDF, particularly when 
coupled with the RhizML syntax.  Maybe we don't really need a new syntax 
for RDF right now, but this does seem to capture a nice balance of 
directness w.r.t. the RDF model, and simplicity.


Do you have any plans for an "RxForms" module?  I.e. some way of allowing 
new information to be entered into defined structures (including definition 
of new structures).  A simple example application would be something like 
foaf-a-matic [2].  (I was working on something like this a while ago, but 
that's rather fizzled out for now as I got distracted by other things, but 
it's something I'd like to revisit.)

[2] http://www.ldodds.com/foaf/foaf-a-matic.html


Can Rhizome use different RDF stores for its back-end?  (I'm thinking of 
Jena, which I know can be called directly from Python, using Jython.  Or 
maybe a Joseki module in Python?)


Overall, based on a quick scan, I think this looks like rather nice work.


Graham Klyne
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Received on Tuesday, 4 November 2003 06:29:02 UTC

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