ExProM Workshop @ COLING 2016
Special Session on Negation
December 12, 2016 - Osaka, Japan
Building a Dictionary of
Affixal Negations
Chantal van Son, Emiel van Miltenburg, Roser Morante (VU Amsterdam)
[email protected]
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Introduction: Affixal negations
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Words marked with negative affix; typically flag
the absence of particular features
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English: un-, in-, dis-, a-, an-, non-, im-, il-, ir-, -less
e.g. unable, disagree, impossible
Automatic detection could benefit NLP tasks
such as text mining, recognizing textual
entailment, paraphrasing and QA
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Introduction: Affixal negations
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Blanco & Moldovan (2011): very difficult to
detect without substantial false positive rate
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how to distinguish between ineffective and invite?
—> check whether word is still valid after removing prefix:
how to prevent inform from being annotated?
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how do deal with ambiguity: invalid (a) vs. invalid (n)?
Automatic detection might benefit from
dictionary-based approach
Eduardo Blanco and Dan Moldovan. 2011. Some issues on detecting negation from text. In Proceedings of the
24th International Florida Artificial Intelligence Research Society Conference , pages 228–233.
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Overview of today’s talk
1. Defining lexical negation
1. affixal negations and regular antonyms
2. typology of affixal negations (Joshi 2012)
2. Building a negation dictionary (preliminary study)
1. annotation tasks
2. evaluation
3. Discussion & Conclusion
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Defining lexical
negation
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Affixal negation
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Morante and Daelemans (2012): annotation of (affixal)
negation in two Conan Doyle stories
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Main goal: to annotate information relative to the negative
polarity of an event (negation + scope)
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‘Narrow’ definition: only annotated if they are direct
antonyms of their non-affixed base
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unclear (not clear)
disappear (*not appear), unspoken (*not spoken)
What is considered an affixal negation should depend on the
task at hand
Roser Morante and Walter Daelemans. 2012. Conan Doyleneg: Annotation of negation in Conan Doyle stories.
In Proceedings of the Eighth International Conference on Language Resources and Evaluation (LREC) .
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Semantic categories (Joshi 2012)
• Joshi (2012): distinction between direct and
indirect affixal negations
• Direct: direct opposition with its positive counterpart
and characterized by the NOT-element (e.g. unhappy)
• Indirect: does not logically negate the existence of its
base, yet still maintains a negative connotation (e.g.
disconnect, debug)
Shrikant Joshi. 2012. Affixal negation – direct, indirect and their subtypes. Syntaxe et semantique, (1):49–63.
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Semantic categories (Joshi 2012)
Table: Subtypes of indirect negation from (Joshi, 2012, p. 27).
Shrikant Joshi. 2012. Affixal negation – direct, indirect and their subtypes. Syntaxe et semantique, (1):49–63.
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Relation to regular antonyms
• Full range of lexical opposites
• The difference between affixal negations and
regular antonyms is only morphological
a. distasteful
b. disgusting
c. dead
(a ‘true’ affixal negation)
(only etymologically an affixal negation)
(a regular antonym)
continuous scale going from explicitly (a) to implicitly (c) marked
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Full range of negation
Figure: Taxonomy of negations, based on (Joshi, 2012)
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Antonymy in WordNet
• Direct antonymy: a lexical relation between
individual lexemes that have clear opposite
meanings (wet:dry, clear:unclear)
• Indirect antonymy: results from similarity relations
defined for the members of direct antonym pairs
(moist:dry, legible:unclear)
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Antonymy in WordNet
Figure: Similarity and antonymy relations in WordNet, from (Gross and Miller, 1990).
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Building a negation
dictionary
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Annotation of WordNet antonyms
• Ideal lexical negation dictionary: regular antonyms + affixal
negations specified for their subtypes
• Starting point: all direct antonyms in WordNet (3,557 pairs,
including verbs, nouns, adjectives and adverbs)
• We included the following information from WordNet:
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the lemmas of both antonyms
the lemma identifiers of both antonyms
the definitions of both antonyms
the part of speech
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Annotation tasks
• Two expert annotators
• Three annotation tasks
1. Affixal or non-affixal
2. Direct or indirect (if affixal)
3. Subtype: 9 subtypes by (Joshi 2012) + additional
label LACKING (if indirect)
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Example of entries
Table: Simplified examples of entries of affixal negations in the dictionary
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Evaluation: IAA
Subtask 1:
Affixal or nonaffixal
n (antonym pairs) n = 500
Subtask 2:
Subtask 3:
Direct or indirect Subtype
n = 268
n = 43
Cohen’s kappa
0.55
0.76
0.80
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Evaluation: confusion matrix
Table: Confusion matrix for the annotation of subtypes
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Evaluation: confusion
Table: Antonym pairs where both annotators recognized an indirect affixal negation but disagreed on the subtype.
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Discussion
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Discussion: doubt case (1)
fasten:unfasten
fastened:unfastened
Reversal of Action
Direct negation
States expressed by participles (adjectives) with a negative
affix can be interpreted as:
A. Indirect negation: a result of the action expressed by its verbal
base (unfasten)
B. Direct negation: the opposite of another state, i.e. its antonym
(fastened)
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Discussion: doubt case (2)
Another example: spinous:spineless
• Affix -less indicates indirect negation (lacking something)
w.r.t. its base spine
• But: spineless is direct negation w.r.t. spinous
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Discussion
• Two options to consider for annotation:
A. relation between affixed form and its base
(spine:spineless)
B. relation between two members of antonym pair
(spinous:spineless)
• In case of (a): what exactly should be considered
the base? E.g. unfastened: fastened vs. fasten
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Discussion
• A negation dictionary is only as good as its
coverage
• Affixal negation is productive phenomenon; what
could be a fallback strategy? —> training a
classifier for detection and classification
• We still need to think about what relations this
classifier should learn (annotation guidelines)
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Conclusion
• Set out the full scope of (lexical) negation
• Explored the possibility of an affixal negation/regular
antonyms dictionary to support automatic detection
• Preliminary study: annotated WordNet’s direct antonym pairs
• No definite solution, but we hope it contributes its share to the
discussion by highlighting some of the main issues to be considered
• The annotations are openly available at: https://github.com/cltl/lexical-negation-dictionary
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Thank you for your
attention
[email protected]
This work was supported by the Amsterdam Academic Alliance Data Science (AAA-DS) Program
Award to the UvA and VU Universities, and by the Netherlands Organization for Scientific Research
(NWO) via the Spinoza-prize awarded to Piek Vossen (SPI 30-673, 2014-2019).
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