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Re: First order logic and SPARQL

From: Adrian Walker <adriandwalker@gmail.com>
Date: Mon, 6 Sep 2010 18:49:51 -0500
Message-ID: <AANLkTi=dvsQi+7vKMd8ZYjkHQrAYp+Nb6GndQ=AN4V+E@mail.gmail.com>
To: Bob MacGregor <bob.macgregor@gmail.com>
Cc: semantic-web@w3.org, public-sparql-dev@w3.org
Hi Bob --

For datalog plus recursion and negation-as-failure, the original
stratification semantics [1,2] is based on the simple idea that one should
rule out proving X with a proof that depends on being unable to prove X.

This can be efficiently enforced with a static syntactic check, so it does
not impinge on runtime efficiency.

                                   -- Adrian

[1]  Towards a Theory of Declarative Knowledge,  K. Apt, H. Blair, A.
Walker. In: Foundations of Deductive Databases and Logic Programming, J.
Minker (Ed.), Morgan Kaufman.

[2]  Backchain Iteration: Towards a Practical Inference Method that is
Simple
    Enough to be Proved Terminating, Sound and Complete.
    Journal of Automated Reasoning, 11:1-22

Internet Business Logic
A Wiki and SOA Endpoint for Executable Open Vocabulary English Q/A over SQL
and RDF
Online at www.reengineeringllc.com
Shared use is free, and there are no advertisements

Adrian Walker
Reengineering



On Mon, Sep 6, 2010 at 6:22 PM, Bob MacGregor <bob.macgregor@gmail.com>wrote:

> Hi Adrian,
>
> I'll let you guys hash out the recursion.  Without it, NAF has a very
> simple semantics
> and implementation.  With it, you need stratified logic, magic sets,
> whatever ...
>
> - Bob
>
>
> On Mon, Sep 6, 2010 at 3:02 PM, Adrian Walker <adriandwalker@gmail.com>wrote:
>
>> Bob --
>>
>> +1 vote for that, but why rule out recursion?
>>
>>                                 -- Adrian
>>
>>
>> Internet Business Logic
>> A Wiki and SOA Endpoint for Executable Open Vocabulary English Q/A over
>> SQL and RDF
>> Online at www.reengineeringllc.com
>> Shared use is free, and there are no advertisements
>>
>> Adrian Walker
>> Reengineering
>>
>> On Mon, Sep 6, 2010 at 3:21 PM, Bob MacGregor <bob.macgregor@gmail.com>wrote:
>>
>>> I would say that the mindset "NAF is not appropriate for SPARQL" is a
>>> piece of the explanation for the
>>> glacial pace of adoption of Semantic Web technology in commercial
>>> settings.  If indeed SPARQL is
>>> supposed to be religiously open-world (I'm not saying I agree), then IMO
>>> that strengthens the argument for
>>> the adoption of a second RDF language, e.g., something like non-recursive
>>> Datalog with negation, that
>>> is more practical/useful.
>>>
>>> Bob
>>>
>>>
>>> On Sun, Sep 5, 2010 at 11:54 PM, Pat Hayes <phayes@ihmc.us> wrote:
>>>
>>>>
>>>> On Sep 6, 2010, at 12:13 AM, Bob MacGregor wrote:
>>>>
>>>> Hi Pat,
>>>>
>>>> On Sun, Sep 5, 2010 at 6:31 PM, Pat Hayes <phayes@ihmc.us> wrote:
>>>>
>>>> On Sep 5, 2010, at 4:48 PM, Bob MacGregor wrote:
>>>>
>>>> > My personal interest is in a query language for RDF that's easy to
>>>> use, and, among other things,
>>>> > has a negation operator that is intuitive.
>>>>
>>>> Id be interested to know what you consider to be intuitive here. Is
>>>> negation by failure intuitive for most Web sources? Do you routinely
>>>> conclude, from a failure to find a sentence asserted on a website, that it
>>>> is false?
>>>>
>>>> Fundamental to your argument seems to be "sentence asserted on a
>>>> website".   If I grabbed
>>>> triples from some random Website, I might not be confident in using
>>>> NAF.  But I don't do that.  I work
>>>> with graphs that I've built from sources I trust, and I know which parts
>>>> of the graph are expected to
>>>> be complete, and NAF is perfect for those parts.
>>>>
>>>>
>>>> Well, bully for you, but SPARQL is supposed to be a standard for use
>>>> with RDF on the Web. These nice assumptions of completeness just where you
>>>> expect it cannot be sustained in the wider world of RDF data, and there is
>>>> no way to transmit them (the assumptions) even when they are correct. So NAF
>>>> is not appropriate for SPARQL.
>>>>
>>>> Pat
>>>>
>>>>
>>>> - Bob
>>>>
>>>>
>>>>  ------------------------------------------------------------
>>>> IHMC                                     (850)434 8903 or (650)494 3973
>>>>
>>>> 40 South Alcaniz St.           (850)202 4416   office
>>>> Pensacola                            (850)202 4440   fax
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>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> =====================================
>>> Robert MacGregor
>>> bob.macgregor@gmail.com
>>> Mobile: 818-397-3468
>>> =====================================
>>>
>>
>>
>
>
> --
> =====================================
> Robert MacGregor
> bob.macgregor@gmail.com
> Mobile: 818-397-3468
> =====================================
>
Received on Monday, 6 September 2010 23:50:24 GMT

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