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From Michael J Gurley <m-gur...@northwestern.edu>
Subject Re: cTakes polarity problem
Date Wed, 31 Dec 2014 16:21:31 GMT
I think this demonstrates that machine learning is not the right approach
to the negation/polarity problem.


Michael Gurley
m-gurley@northwestern.edu
312 925 3268
Northwestern University Clinical and Translational Sciences Institute
(NUCATS)
http://www.nucats.northwestern.edu
Rubloff Building
750 N Lake Shore Drive, 11th Floor
Chicago, IL 60611







On 12/31/14 9:13 AM, "Miller, Timothy"
<Timothy.Miller@childrens.harvard.edu> wrote:

>Hi Yu,
>
>The new polarity module is machine-learning based so it is not always
>easy to diagnose accuracy issues. But generally it might mean there was
>no example like that in the training data. It was trained on multiple
>corpora, but sometimes certain phrases slip through the cracks, and
>"Deny hepatitis," while possible in the truncated language of clinical
>notes, seems like an unlikely phrase and so it may not be in our data.
>Is that a real example you saw or just a minimum (not) working example?
>If not do you have a real example (i.e. a whole sentence) where "deny"
>should cause a negation but does not? If so I will look into it. We have
>had a few reports like this so it may be worth keeping track of missed
>examples for future iterations of the module. It is important that they
>be real examples "from the wild" though.
>
>(As an aside, machine learning methods don't understand language the way
>people do so even if it seems obvious to a human that "Deny <disease>."
>should be negated, if it looks different enough from the context of an
>example from the training data the ML will sometimes fall back to the
>majority class of "Not negated".)
>
>Tim
>
>
>On 12/31/2014 10:03 AM, Yu Liang wrote:
>> I have a quick question about CTAKES.
>> I am using AE ³AggregatePlaintextUMLSProcessor.xml² and want to get
>>some negation results by referring to polarity attribute.
>> However, it turns out, for example ³Negative for hepatitis², is not
>>negated. I think it is weird and I tried ³No hepatitis², ³ Denies
>>hepatitis² which return ³polarity= -1², but ³Deny hepatitis.² returns
>>³polarity=1².
>>
>> any one could give me some clue that what is wrong? Thank you!
>


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