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Re: comment on /2001/11/13-RDF-Query-Rules/ re 'single arc languages'

From: Eric Prud'hommeaux <eric@w3.org>
Date: Tue, 18 Mar 2003 16:56:57 -0500
To: Libby Miller <Libby.Miller@bristol.ac.uk>
Cc: Dan Brickley <danbri@w3.org>, www-rdf-rules <www-rdf-rules@w3.org>
Message-ID: <20030318215657.GD7015@w3.org>

On Tue, Mar 18, 2003 at 09:39:13PM +0000, Libby Miller wrote:
> 
> I think Versa might be one of these 'single arc' types - see
> http://uche.ogbuji.net:8080/uche.ogbuji.net/tech/rdf/versa/versa.doc?xslt=/ftss/data/docbook_html1.xslt
> 
> and especially
> http://uche.ogbuji.net:8080/uche.ogbuji.net/tech/rdf/versa/versa-by-example.txt
> 
> Libby

Versa and TAP were my only examples. Beyond that, the obvious wrapping
of a serialization protocol around an API.

> On Tue, 18 Mar 2003, Dan Brickley wrote:
> 
> >
> > Eric,
> >
> > I'm reviewing http://www.w3.org/2001/11/13-RDF-Query-Rules/
> >
> > Rather than try to prepare a single detailed review, I'm sending
> > separate msgs on particular bits as and when I grab time to do this. If you'd
> > rather I tried to make a more unified review doc, I could do that. The
> > current approach seemed a quicker way to make gradual progress...
> >
> >
> > So first thing I wanted to ask about:
> >
> > Under "Goal Characteristics", you distinguish...
> > [[
> > graph or arc
> >     Some languages express a single arc, others an open subgraph.
> >     No observed single arc languages support variables. This
> >     leaves them unable to answer the specific query
> >     represents(?x ?x) "What lawyers represent themselves?" but
> >     instead the more general question represents(?x ?y) "What
> >     lawyers represent anybody?". At this point, all single
> >     arc query languages are outside the scope of this survey.
> > ]]
> >
> > This paragraph makes me curious. You rule discussion of these languages
> > out of scope, and don't cite any. Are they a theoretical rather than
> > actual possibility? In my experience 'single arc' functionality is only
> > exposed via RDF APIs, rather than textually represented query languages.
> > I don't know of any actual 'single arc' query syntaxes, though perhaps
> > some of the path-oriented efforts might fall under this heading?
> >
> > Your claim that "No observed single arc languages support variables" would
> > carry more oomph if you listed some observed single arc languages. Can you
> > give examples? Even if for the purposes of ruling them out of scope for
> > detailed analysis. If there aren't any, this is probably worth noting.
> >
> > Dan
> >
> > ps. you also have "some languages" in the first entry, and "some query engines"
> > in the second, under "Goal Characteristics".

fixed - tx

>                                                Are you comparing query
> > languages or software designs / implementations? (these have tended to be
> > 1:1 in recent history, I guess...). My assumption is that the focus here is
> > on language comparison.

languages, mostly
there's a section for implementation characteristics

[1] http://www.w3.org/2001/11/13-RDF-Query-Rules/#implChar
-- 
-eric

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Received on Tuesday, 18 March 2003 16:57:01 GMT

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