|To:||"Ogbuji, Chimezie" <OGBUJIC@xxxxxxx>|
|Cc:||semanticweb@xxxxxxxxxxxxxxx, "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>, public-semweb-lifesci hcls <public-semweb-lifesci@xxxxxx>, semantic_web@xxxxxxxxxxxxxxxx, welty@xxxxxxxxxxxxxx|
|From:||Pat Hayes <phayes@xxxxxxx>|
|Date:||Thu, 26 Jun 2008 20:17:42 -0500|
At 6:31 PM -0400 6/26/08, Ogbuji, Chimezie wrote:
Hey, Pat. Comments below
Juat as an aside, its hardly fair to this in RDF which doesn't have negation of any kind.
that the question was asked.
Well, let me push on this. Lets suppose that whoever wrote the record did indeed know this, and they used the 'if I don't say it, its false' strategy, saving themselves some work. But now, this is all written down in RDF. Send this RDF somewhere else, where someone else reads it. How do they know that its OK to use NAF on this RDF? The RDF itself doesn't describe the nurse's data-recording conventions, and it doesn't say that its a closed world with respect to having headaches. All it does is not refer to headaches at all. There might be any number of reasons for this. Maybe the nurse just didn't think about headaches, maybe (like my wife's endocrinologist) the doctor just didn't consider headaches to be in his focus of attention. Maybe this RDF was extracted from a larger data set by a SPARQL query which didn't happen to refer to headaches. In general, you *don't* know anything more than what is *explicitly told* to you. At any rate, that has to be the ground assumption of an ontology engine, especially in a Web setting where you have absolutely no control over what happened to the data while it was on its way to you, and nobody is under any obligation to tell you.
The assumption that knowledge is *always*
But if that completeness is not somehow recorded as part of the data, then all the control in the world isn't going to justify a later or distant process of *inference*. Because this control - or its effects on what the data say - is itself part of the information that this inference needs to rely on. Its not enough to just be careful; you have to record the fact that you are being careful along with the carefully controlled results of your carefulness.
have decent control over the quality of the data in general or at least
Modify that to: if the person doing the analysis knows that decent control, etc. , and I will agree.
how the data is collected.
knowledge is *always* incomplete regardless of how you come about it.
There is a kind of Web Doctrine that SWeb methods must be monotonic because the Web is open-ended and you might get more information later, after you make any inference. But this is more of a kind of methodological justification than a serious factual claim, I think.
Well, OK, but give me a little bit of CL/IKL slack and I'll axiomatize your carefulness principle for you so that your nurse doesn't have to do any extra work. Let suppose there are some data recording protocols which work the way you sketch above. We can actually describe them:
(forall ((X protocol) (D Dataset) P)(if
Now all your dutiful nurse has to record is that her records were constructed using a protocol which is Completable wrt the property of having a headache, which is no doubt itself recorded in the home ontology describing the protocol:
LowCostMeds:method1 :a ama:CompletableProtocol .
LowCostMeds:HasAHeadache :CompletionPropIn LowCostmeds:method1 .
so the nurse just has to record her data in an RDF graph with a URI like
and include in the graph the self-referring assertion
SacreBleu:1263Xf5-220807 ama:ConstructedUsing LowCostMeds:method1 .
(which is actually going to be done by her computer) and now all the no-headache conclusions follow by classical reasoning.
Well, provided that you somehow record the fact that this process was used, so that the right conclusions can be drawn from the data. And then, if you do this right (cf above) its all classical reasoning again.
>reacting against some of the more tedious notational results
I don't agree. If you do the data recording responsibly, it always comes out as classical reasoning. And its never responsible to use NAF unless you know that the data justifies closed-world reasoning. BUt if you know this, it should be recorded somehow as part of the data: and if it is, then the reasoning isn't using NAF any more, but classical negation. Operationally it feels the same, but its all classical logic (which is a very nice thing, btw, as this is the only logic with a universally agreed semantics.)
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