Using Signals to Improve Automatic    Classification of Temporal Relations                      
Time in language    ●   In natural languages, significant effort is devoted to         describing time (tense, aspect, adv...
 Temporal AnnotationWhat to annotate?    ●   Events and time expressions (intervals)    ●   Temporal, aspectual and subord...
Temporal signalsTemporal links between intervals (TLINKs) specify a relation – BEFORE, AFTER, INCLUDESImplicit sources of ...
Baseline and corpusThe TLINK classification task is difficult:    ●   TempEval­1:  59%    ●   TempEval­2:  61%    ●   Most...
Feature setTo augment the baselines features with information about signals:    ●   Signal phraseTextual position of event...
ResultsAdding signals to our feature set improved overall performance from 60.32% to 61.46% ­ marginal improvement.Explana...
ConclusionSignals as described by us are helpful to the TLINK classification task.Future work     ●   Automatically annota...
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Using signals to improve automatic classification of temporal relations

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Temporal information conveyed by language describes how the world around us changes through time. Events, durations and times are all temporal elements that can be viewed as intervals. These intervals are sometimes temporally related in text. Automatically determining the nature of such relations is a complex and unsolved problem. Some words can act as “signals” which suggest a temporal ordering between intervals. We use these signal words to improve the accuracy of a recent approach to classification of temporal links.

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Using signals to improve automatic classification of temporal relations

  1. 1.   Using Signals to Improve Automatic Classification of Temporal Relations   
  2. 2. Time in language ● In natural languages, significant effort is devoted to  describing time (tense, aspect, adverbials). ● We have occurrences and states which we can temporally  “position” or ask about. ● Events, points and periods in time can all be related with  language. ● Understanding and processing this information is difficult. ● How can we formally describe time in language?   
  3. 3.  Temporal AnnotationWhat to annotate? ● Events and time expressions (intervals) ● Temporal, aspectual and subordinate links between intervals ● Signals that indicate recurrence or temporal orderingTimeML is a formal specification for annotating these kinds of entityTimeBank is an annotated corpus of ~65 000 tokens   
  4. 4. Temporal signalsTemporal links between intervals (TLINKs) specify a relation – BEFORE, AFTER, INCLUDESImplicit sources of information for TLINKs: ● Tense/aspect ­ “I had showered and I left.” ● World knowledge ­ “Ben pulled out a gun. The smell of  cordite filled the air.”We also have explicit information from signals. ● “The road was built. Subsequently, travel time improved.”We hypothesize that signal words can be described as features to improve TLINK classification.   
  5. 5. Baseline and corpusThe TLINK classification task is difficult: ● TempEval­1:  59% ● TempEval­2:  61% ● Most­common­class:  50­55%We replicated established recent work, using a merge of TimeBank v1.2 and the AQUAINT TimeML corpus. ● Event­event TLINK classification: 60%   
  6. 6. Feature setTo augment the baselines features with information about signals: ● Signal phraseTextual position of event word and signal can affect temporal interpretation of a relation: ● “I run before I sleep” ● “Before I run I sleep”We capture ordering using these features: ● Arg1 / signal order ● Signal / Arg2 order ● Token distance between arg1 / signal / arg2   
  7. 7. ResultsAdding signals to our feature set improved overall performance from 60.32% to 61.46% ­ marginal improvement.Explanation:Only 5.1% of TLINKs in evaluation data use a signal – the corpora show strong evidence of under­annotation.So, we split our data into TLINKs with and without signals. ● On unsignalled links, performance remained the same ● On signalled links, we saw a jump to 82.19% classification  accuracy   
  8. 8. ConclusionSignals as described by us are helpful to the TLINK classification task.Future work  ● Automatically annotate signals ● Add more sophisticated features for signals ● Repair some under­annotation in TimeBankThanks ­ Any questions?   

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