cTAKES also implements a rule-based approach to the negation/polarity problem. It was the default until the latest release. You are free to use the rule-based implementation and compare results with the ML approach. --Guergana
-----Original Message----- From: Michael J Gurley [mailto:[email protected]] Sent: Wednesday, December 31, 2014 11:22 AM To: [email protected] Subject: Re: cTakes polarity problem I think this demonstrates that machine learning is not the right approach to the negation/polarity problem. Michael Gurley [email protected] 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" <[email protected]> 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! >
