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Re: Editorial thread for BGP matching

From: Pat Hayes <phayes@ihmc.us>
Date: Mon, 23 Jan 2006 11:17:38 -0600
Message-Id: <p06230902bffabb25887d@[10.100.0.23]>
To: Enrico Franconi <franconi@inf.unibz.it>, Andy Seaborne <andy.seaborne@hp.com>
Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>

>On 21 Jan 2006, at 20:43, Enrico Franconi wrote:
>
>>
>>I propose to have an explicit text to present the reader the 
>>alternative semantics

Its only an alternative form of words which gets the same result. The 
semantics isn't changed at all.

>>by Pat in a simple way, immediately before "As an example of a 
>>Basic Graph Pattern:", as follows:
>>
>>"In the case of simple entailment, if the scoping graph G' is such 
>>that it does not share blank nodes with BGP, then the above 
>>definition can be simplified to use a standard RDF merge instead of 
>>an OrderedMerge."
>
>Ooops! I meant a union, not a merge!
>
>"In the case of simple entailment, if the scoping graph G' is such 
>that it does not share blank nodes with BGP, then the above 
>definition can be simplified to take the union between G' and BGP, 
>instead of an OrderedMerge."

This works for any kind of entailment, which is why I prefer the 
simpler wording: and then we don't need this odd notion of ordered 
merging at all. In fact, I'd suggest that the simpler wording should 
be normative, as it expresses the intended meaning more directly and 
straightforwardly. Also, it keeps distinct issues separate. Exactly 
how an engine handles bnode scoping (what gets re-written, or maybe 
use hash-tables, whatever) really is an implementation decision. We 
shouldn't build into the entailment clause what is in effect an 
implicit decision about how to implement bnode scoping.

Pat

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Received on Monday, 23 January 2006 17:17:45 GMT

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