[Versa] More on literal queries

[Michael Olson]

>
> I think I follow about 50% of all this (again back to my comments about
> RDF having turned itself into an inscrutable mess).
>
> My position comes from the simplest point of view.  I would be bloody
> surprised if the result of an XPath query "3.0" was the empty node set
> just because I didn't happen to have that literal value anywhere in my
> XML.
>
> I daresay any user would be surprised to see the same weirdness in
> Versa.
>

What is the purpose of the query "3.0"?  Is it just to fire up the old  
parser to make sure it work?  Because you would not get any meaningful  
information from the RDF model from that query.

So, we should either not support it, unless like in the case of XPath  
it becomes easier to support it then not support it, or we should have  
it be a meaningful query.  To me, it is a meaningful query and nice  
short hand over

filter(all(),type(rdfs:Literal),eq("3.0"))



> I will comment on one thing you say:
>
>> If however, we wish to support a higher level of semantics in the  
>> Versa
>> language, then I see no other path then to use the rdf semantics as a
>> guide.  If we don't, then how do we expect others to implement Versa  
>> as
>> a RDF query language if the language itself is not designed to work
>> with a RDF model?
>
> One thing I do know about the battle to turn RDF into CGng is that RDF
> was *not* changed to assert a closed world assumption.  Whether or not
> someone chooses closed or open world assumptions is up to them.
>
> As such, there is nothing in the RDF semantics that says that "if
> one particular graph does not have an instance of a resource, that
> resource does not exist".  If there were, it would not work for the  
> Web.
>
> In short, I don't believe there is anything in RDF semantics that
> mandates the closed world context you're advocating.
>

I guess I don't follow you.  Nothing I've said is closed world in my  
mind.   I've never stated that if the resource does not exists in our  
model then it exists no where.  What I did state is that if you query  
the model for that resource and it does not exists in that model, then  
the results should be an empty set.

Are you saying that the results should always contain the resource  
because we must assume that it exists some where?  I hope not because  
that would be silly.

Mike


>
> --  
> Uche Ogbuji                               Fourthought, Inc.
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> XML Output with 4Suite & Amara -  
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>
------------------------------------------------------------------------ 
-----------------
Mike Olson                                                Principal  
Consultant
mike.olson at fourthought.com                +1 720 253 4662
Fourthought, Inc.                                       
http://Fourthought.com
PO Box 270590,                                       http://4Suite.org
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