W3C home > Mailing lists > Public > public-rdf-dawg@w3.org > October to December 2004

Re: tests and inference? (and UNSAID)

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Thu, 23 Dec 2004 11:52:19 +0000
Message-ID: <41CAB173.2030909@hp.com>
To: Pat Hayes <phayes@ihmc.us>
Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>

Pat Hayes wrote:
>> On Wed, Dec 22, 2004 at 10:32:11 +0000, Andy Seaborne wrote:
>>>  >>FROM could make sense - the server offers a numer of graphs and the
>>>  >>URI in teh FROM must choose one of them.  If it names some graph the
>>>  >>server is not publishing, then the query generates an error.  FROM
>>>  >>isn't a requirements to load any graph (I worry about the security
>>>  >>issues of that).  A server may require that there is only one URI in
>>>  >>the FROM clause - i.e. no arbitrary RDF merge of graphs.  It is 
>>> just a
>>>  >>request for something that the server does not offer.
>>>  >
>>>  >
>>>  >Agreed. I think we should allow a server to refuse to answer a 
>>> query if
>>>  >it names FROM a graph that the server cannot (prefers not to) access,
>>>  >and we should allow the query to provide a variable in the FROM 
>>> position
>>>  >which gets bound to the name of the source as part of the answer, so
>>>  >that a query can say, in effect: answer this from any source you 
>>> choose,
>>>  >but tell me what the source was.
>>>  Woudl using "SOURCE ?src { ... query pattern ... }" achived this 
>>> effect if
>>>  the query is over the collection of named graphs?
>> I would hope so, named grpahs or not.
>>>  >Query-answering servers should be
>>>  >required to provide a binding to any such variable, even if it is a
>>>  >'trivial' one which simply identifies the server itself (which means,
>>>  >roughly: I am the source, and that's all you are going to get out 
>>> of me
>>>  >on that topic.)
>>>  Interesting - this is saying the default graph has a URI.
> Default graph?? That sounds like a horrible idea.  Where did that come 
> from? I don't remember seeing anything in the draft about default graphs.
> (What is entailed by the default graph? Or would those only be default 
> entailments? If I already have a graph, can I import the default graph 
> into it by default?)
> Pat



A datset is one unnamed graph, which is what patterns match against when 
there is no SOURCE being applied.  A dataset also has a number (0+) of named 
graphs and you access them with SOURCE.

"default" isn't a gerat name - "unnamed"? maybe.  "main"?


>>  >
>>>  I wonder how that interacts with the protocol.
>> I interpreted that part of the protocol as refering to the KB level, ie.
>> the level at which triples dont interact. Though I contradicted that in a
>> previous mail. Must learn to stop sending mail pre-coffee.
>> - Steve
Received on Thursday, 23 December 2004 11:52:48 UTC

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