Re: subgraph/entailment

On 19 Sep 2005, at 23:32, Pat Hayes wrote:
>> Though it took some work to get there. I've been testing this account  
>> with various people who are actively concerned with querying, albeit  
>> typically against more expressive languages such as OWL. *Serious*  
>> confusion ensues.
>
> Hmm, I wonder why. This has seemed kind of obvious since early in the  
> entire RDF process, surely? BTW, have you tried talking to people who  
> are familiar with SQL querying?

That would be me :-)
I argued elsewhere about SQL  
<http://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2005Sep/ 
0072.html>.

>>  While I understand that the charter rules out specification of the  
>> more expressive bits (though, frankly, I could junk that; I don't see  
>> that it's a *useful* constraint)
>
> Ah, there we differ. I see it as central. The primary purpose of  
> SPARQL is to help get RDF deployed in real applications.

Of course, but this does not mean that we can not get also  
interoperability with OWL-DL like languages, without losing the  
efficiency of SPARQL for your "syntactic" based queries.

> Most of the people working on these applications will not be using  
> more expressive languages in any depth, and are not interested in  
> inference or entailment.

I find this statement very dangerous to say to a semantic web  
community. Of course, we want efficient systems, but ideally we also  
want a semantics behind them. Having no interest in semantics or  
entailment really means that there should be no interest in *semantics*  
seriously speaking, so why bother with your long RDF-MT document :-)

> If SPARQL gets used for a few years and then a completely different  
> protocol is developed for 'logical' querying, I will be quite happy:  
> it will have done its job. If SPARQL is warped or delayed just to  
> provide it with a logically clean extension path, that warping or  
> delay is doing far more harm than good, IMO.

Our plan is not to delay or to change what has been already done. It is  
just about giving a nice logic based semantics to what has been done in  
a way that also opens new possibilities for well founded extensions.
So, I agree with your concerns, but if we wark together we can have the  
cake and eat it too!

> For myself, apart from the small group of logic police, whose  
> objections I can script in advance, *nobody* I have chatted with has  
> evinced the slightest interest in any formal semantic issues at all.
> They tend to regard such matters as arcane academic baloney.

So, why did you give us the nice RDF-MT document? This is a very strong  
statement. I guess we are working with the same spirit. And, by the  
way, it is not nice to use terms like "logic police"; I'd like to have  
more politeness in our discussion.

>> ). A virtual graph approach, suitably described, might work as well  
>> for these audience. But the current document is *not* adequate on  
>> this front.
>
> I wish to know why, and in what regard, it is inadequate. All the  
> objections I have read so far have been to the effect that there MUST  
> be a semantic story which makes querying into a species of  
> entailment-checking: and this view is, IMO, both wrong and (in the  
> SPARQL context) wrong-headed. It is false for SQL, probably the most  
> widely used query language ever.

See again above my comments on SQL.

cheers
--e.