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An Alignment-based Pattern Representation Model for Information Extraction
1. An Alignment-based Pattern Representation Model
for Information Extraction
Seokhwan Kim, Minwoo Jeong, Gary Geunbae Lee
{megaup, stardust, gblee}@postech.ac.kr
Abstract - In this paper, we propose an alternative pattern representation model and the effective method of utilizing it. While the previous pattern
representation models completely depend on the result of dependency analysis, our approach is basically based on the lexical alignment and
considers the result of dependency analysis only as a meaningful feature of the alignment process. In this way, we can cope with the errors of
incomplete dependency analysis. An evaluation of a scenario template task shows that our proposed model outperforms the previous
syntax-dependent models.
Pattern Representation Model for Information Extraction
Information Extraction Pattern Representation Model for IE Related Works
Extracting the defined number of relevant Problem Definition Lexical Sequence Pattern Models
arguments from natural language documents Ex) A set of lexical sequences
Subtasks <hum_tgt> be kidnapped
About 50 peasants have been kidnapped by terrorists of the FMNL
be kidnapped by <prep_ind>
# of arguments subtask
1 named-entity recognition Extraction Pattern Syntax-dependent Pattern Models
2 binary relation extraction ? A set of subtrees (from D-tree)
more than 2 relation/event extraction
incident type kidnapping kidnapped
Approach prep_ind terrorists nsubjpass agent
Automatic Pattern Learning prep_org FMNL peasants terrorists
hum_tgt peasants
Pattern Representation Model prep_of
Pattern Learning Algorithm (kidnapped ({HUM_TGT}-nsubjpass) FMNL
(kidnapped ({PREP_IND}-agent))
(kidnapped ({PREP_IND}-agent ({PREP_ORG}-prep_of)))
Method
Our Approach Pattern Sequences Extraction
Pattern Model 1) Searching the sentences containing all Ex) (3+1)/(0+1) = 4
Lexical Sequence Pattern arguments of each tuple in source documents
2) Segmenting out subpart of the sentence kidnapped
+ Term Weight (from Dependency Analysis)
based on clausal boundaries nsubjpass agent
<HUM_TGT> of [NP] have been kidnapped by <PRED_IND>
3) Replacing the parts of arguments in the
(1+1)/(1+1) = 1 (2+1)/(1+1) = 1.5
1 0.33 0.33 4 4 4 1.5 1.5
sub-sentence with argument labels
Computing Term Weights <HUM_TGT> <PREP_IND>
Soft Pattern Matching
Sequence Alignment wi = (ri + c) / (di + c) prep_of prep_of
about 50 peasants have been kidnapped by terrorists wi : weight of i-th term
ri : number of relevant terms within [NP] <PREP_ORG>
a subtree, ti as root
<HUM_TGT> of [NP] have been kidnapped by <PREP_IND> di : distance from root node (0+1)/(2+1) = 0.33 (1+1)/(2+1) =0.67
c : for smoothing (default:1)
Experiment
Pattern Matching
Sequence Alignment Experimental Setup Experimental Result
Based on a Dynamic Programming Data Pattern Models
Alignment Matrix MUC-3/4 Data SVO Model (Yangarber ‘00)
peasants have been kidnapped by terrorists About the Terrorism Events Linked-Chain Model (Greenwood ‘06)
<HUM_TGT> 1 0 0 0 0 0
of 0 1 0 0 0 0
Simpler template structure with 4 slots Subtree Model (Sudo ‘03)
[NP] 0 0.66 1 0 0 0 perp_ind, perp_org, phys_tgt, hum_tgt Our Model
have 0 4 3 2 1 0
been 0 0 8 7 6 5 Dev-set (training), Test-set (evaluation) Result
kidnapped 0 0 4 12 11 10 Preprocessing Model Precision Recall F-measure
by 0 0 0 8 13.5 12.5
<PRED_IND> 1.5 0.5 0 0 0 15 Dependency Parsing and NP-chunking SVO 21.74 20.62 21.16
Stanford Parser Linked-Chain 20.04 26.55 22.84
Matrix Computation Extracting Pattern Candidates Subtree 23.34 32.73 27.25
Alignment 23.35 45.62 30.89
Mi-1,j-1 + sim i-1,j-1 * wi-1 Selecting all pattern candidates for test
Mi-1,j + gp * wi-1 Without pattern filtering Our proposed model achieved much
Mi,j = max
Mi,j-1 + gp * wi To compare not the pattern filtering higher recall than the other models with
0 method, but the representative performance similar precision
among pattern models