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Re: RIF-in-RDF: Requirement 4 [Switching to KR Argument]

From: Michael Kifer <kifer@cs.stonybrook.edu>
Date: Sun, 25 Jul 2010 22:30:58 -0400
To: Sandro Hawke <sandro@w3.org>
CC: public-rif-wg <public-rif-wg@w3.org>
Message-ID: <20100725223058.07e7c8e5@kiferserv>
OK, I think I am getting closer. You should have started with this.
So, it is not a matter of inference and its completeness but rather
of which rule exactly a particular RDF graph encodes, right?

That is, if we do not use lists explicitly in RDF then there is no way to encode


correctly? That it will be instead be encoding a set of rules that in addition
includes  a&b=>d, a&c=>d, a=>d, etc.

This looks like a strong argument. I haven't thought about it.

Dave, Harold, do you see a way around this problem?


On Sun, 25 Jul 2010 22:10:52 -0400
Sandro Hawke <sandro@w3.org> wrote:

> I think we're misunderstanding each other.   It's possible I'm just
> wrong (as you seem to think), but I don't think so.   I can try to
> refine my language, but it's not clear to me how to do that right now.
> So let me try a completely different line of argument for a minute.
> Please try to read between the lines of my poor command of the language
> of philosophy and formal logic:
>   1. RDF is a KR.  An RDF graph is a logical statement; it makes claims
> about some world.
>   2. If someone makes a claim by stating RDF Graph G, they are implying
> all the claims made by all the graphs entailed by G.
>   3. While there may be some debate about which logics (and therefore
> which entailments) are appropriate/standard, RDF Simple Entailment
> certainly is.  So whenever you say something as an RDF Graph G, you are
> implying all the claims of all the subgraphs of G.
>   4. Assume we have the RIF rule, a&b&c=>d, and it's encoded in graph G
> as node R. This means the agent stating G is claiming that R says
> a&b&c=>d.  
>   5. If we use the repeated-properties mapping for that step-4 encoding,
> then there will be subgraphs of G which describe R as saying a&b=>d,
> a&c=>d, a=>d, etc.  
>   6. If the agent stating G is also asserting R, then (by #5) the agent
> is also implying a&b=>d, a&c=>d, c=>d, etc.    If c is true, the agent
> will have implied d.   Consumers trusting that agent may justifiably
> infer d.  If it turns out a or b was false, this conclusion is wrong.
> So, this is bad.
>   7. With the list-style mapping, the only subgraphs of G in which R
> encodes a RIF Document are those in which that encoded document has the
> same RIF meaning.  This is because the list-style mapping is essentially
> fragile; all the non-trivial subgraphs simply don't describe a RIF
> document.   So we avoid #6 badness.
> I'm sorry I don't know how to say this in the proper mathematical
> language.  I hope it still makes sense.  Let me know which steps I need
> to expand on/clarify.
>      -- Sandro
Received on Monday, 26 July 2010 02:31:32 UTC

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