Approach

TASK 1 – SYNTAX ANALYSIS: THE SCOPE OF A NEGATION

THE SCOPE OF A NEGATION

( See file negation_conversion.py )

Step 1:

We find the scope by searching for its start word and its end word with the find_portee(doc) method. We first search for the negative words in the sentence and then find their head words in the dependency tree. For each head word found, we check that it is not a negative word by checking if its label is not ‘neg’ and if it does not belong to our list of negative words to avoid giving it a NOT_ prefix later. And we end by returning its start word and its end word.

Step 2:

Going through all the words in a sentence, we look to see if the word has a negative meaning using POS tagging in Spacy[1] or if this word is in the negative word list that we built in order to capture negative scopes not detected by Spacy.

List of negative words:
word_negatifs = [ "no", "No", "not", "Not", "without", "never do", "Never", "Without", "none", "None", "nothing", "Nothing", "hardly", "hardly be", "barely", "n't" ]

In addition, we have constructed a list of words and punctuation marks designating the end of a negative scope in order to identify the end of a negative scope to avoid certain errors in dependency analysis.

List of words and punctuation marks:
word_portee = [ "but", "as","liked","even", "which", "and", "while", "why", "." ]

Step 3:

We try to convert the sentence by checking each word in it.

• We do nothing if:


• The word is in the constructed list of stop words of the negative scope


• The word is in the list of stop words of the negative scope of the tree


• We apply the NOT_ prefix to the word if:


• The word is in the list of words of the negative scope of the tree


• Otherwise we apply the NOT_ prefix to the word

Once all the words have been processed, we reconstructs the sentence by adding a space in front of each word in the list and returns this sentence.

Examples

( See APPENDIX 1 – Results of task 1 )

Using displaCy we were able to display the dependency tree for each of the sentences in order to study them[2].

This sentence has two negative staves, one that begins with the word “no” and ends with a comma and the other begins with “not” and ends with a period.

This negative stave begins at the beginning of the sequence and ends with a comma.

Difficulties encountered

Build the negative scope using the dependency tree and not using a list of negative words.

Handle the various special cases that led us to false.

We fixed this:

• A negative scope that is not recognized in the dependency tree:
Conversion: I hardly recommend to you Abitazione Pigneto .
Real phrase: I hardly NOT_recommend NOT_to NOT_you NOT_Abitazione NOT_Pigneto .

• Small details like punctuation marks at the end of a sentence :
Conversion: Should n't NOT_it NOT_be NOT_minor NOT_league NOT_?
Real phrase: Should n't it be NOT_minor NOT_league ?

We chose (due to lack of time) not to resolve this:

• The application of the _NOT prefix in some cases is not immediately after a negative word.
Conversion: A bigger difference could hardly NOT_be NOT_imagined .
Real phrase: A bigger difference could hardly be NOT_imagined .

• Spacy tokenization errors:
Conversion: I have tried for two weeks without NOT_a NOT_returned NOT_e NOT_- NOT_mail and none NOT_have NOT_come NOT_back
Real phrase: I have tried for two weeks without NOT_a NOT_returned NOT_e-mail and none NOT_have NOT_come NOT_back

• A poorly detected end of range:
Conversion: I am barely NOT_able NOT_to NOT_stay awake while reading it .
Real phrase: I am barely NOT_able NOT_to NOT_stay NOT_awake while reading it .

We could not solve this:

• Adding a space at the beginning::
Conversion: I can cook all these things without NOT_a NOT_book .
real phrase: I can cook all these things without NOT_a NOT_book .