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Re: Wording change (was : Re: Final text for Basic Graph Patterns)

From: Enrico Franconi <franconi@inf.unibz.it>
Date: Thu, 19 Jan 2006 02:50:08 +0100
Message-Id: <210C2AEA-07BE-49E0-980D-AAF0A723298A@inf.unibz.it>
Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>
To: Pat Hayes <phayes@ihmc.us>


On 19 Jan 2006, at 00:15, Pat Hayes wrote:
> Anyway, see what y'all think of that. We have until next Tuesday to  
> argue about it :-)

As it is, it does not work. Now, please, allow me the following. I am  
serious.

<rant>
To be honest, you can not pretend to change your mind every few days,  
throw at us super-verbose sloppy definitions, have me read them,  
enter in your head, understand, and then I have to say that they do  
not work. It's going on this way since three months, and I simply  
can't spend too much time with you, OK?
It's almost 3 in the night, I spent almost one hour to answer, and I  
am tired, I already fixed your yesterday's version this morning.
Do you want to see me dead?
</rant>

The rant is to let you know about my inability to work in this way,  
and it is not intending to judge your behaviour.

> that we have some leeway with specifying the scoping graph which we  
> can utilize, in particular we can require that the scoping graph be  
> standardized apart from the BGPs. So suppose it is. Then we can  
> replace
>
> S(G' OrderedMerge BGP)
>
> by
>
> (G' union S(BGP))
>
> in the definitions, which is clearer and more intuitive.

You can't have the told-bnode case anymore with your wording.
Since it's so late in the night, I leave the easy proof of this as an  
exercise to the students.
Hint: the told-bnode case is about coreferencing bnodes in the query  
with bnodes in the graph; without a formal function relating the two  
(in our case, the OrderedMerge, where you can fix some of the  
renamings - see our 2nd November document) you can not express  
formally this relationship. I am sure that you understand the scoping  
graph to avoid the merge, but not having the merge anymore does not  
allow you to define which bnodes should not be renamed, when they  
play the role of told bnodes in the query.
On the other hand, the only role for which I find the scoping graph  
useful is because you want to distinguish the told-bnode case with  
the one where bnodes can be arbitrary. Of course, the equivalence  
theorem with the subgraph matching implementation (done by most  
system, and standard in the LC design) holds only in the case of the  
told-bnode (i.e., when G=G'). Ah.

Is it fixable? Who knows, probably yes, with some other lenghty  
proposal you may throw at us.

And by the way, I wouldn't call this only a wording change ;-)

I stick to my proposal of this morning - of course, editorial changes  
are welcome (for example, I accept the critique of using the word  
'default'; but I want to leave clear the idea that simple entailment  
is essentially about reading the structure of a graph with anonymous  
labels (the bnodes), as opposed to entailments that consider the  
semantics of RDF or RDFS or OWL).

--e.
Received on Thursday, 19 January 2006 01:50:25 GMT

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