KR101241330B1 - Method for recognizing relation based on PAS(Predicate-Argument Structure) and apparatus thereof - Google Patents

Abstract

Provided are a method and apparatus for extracting a relationship using a lexical pattern based on a PAS (Predicate-Argument Structure).
According to an embodiment of the present invention, there is provided a method of predicting a relationship between objects to obtain a PAS pattern representing a significant relationship between two entities in a sentence by analyzing a predicate-argument relationship of a sentence; Generating a feature vector by using the extracted predicate-argument pattern by using a predicate word, an argument word, a kind of predicate, and a relationship label between the predicate and the argument; And inputting the feature vector into a machine learner to identify semantic relations between objects.
In the method and apparatus for identifying a relationship according to the present invention, the PAS pattern may be usefully used in a high-level natural language processing application such as information extraction, automatic summary, and question and answer, in which the meaning of a sentence plays a key role.

Description

Method for recognizing relation based on predicate-argument structure (PAS) and apparatus approximately}

The present invention relates to a method of identifying a relationship between entities existing in a document, and more particularly, to a method and apparatus for identifying a relationship using a lexical pattern based on a predicate-argument structure (PAS). .

Information extraction is a key area in natural language processing and text mining. The final goal of information extraction is to identify important and relevant information present in the text to extract and transform the tabular structured data within the unstructured text data. The element technologies constituting such information extraction techniques include (1) Named-Entity Recognition, (2) Relationship Extraction, and (3) Co-reference Resolution. Among these, relationship extraction is recognized as the most difficult unsolved field to date.

So far, various supervised learning based relationship extraction techniques have been introduced to improve the performance of relationship extraction. They can be classified into three types: (1) rule-based methods, (2) feature-based methods, and (3) kernel-based methods.

As a relatively recently developed method, the effects of a kernel-based method of newly constructing a kernel function specialized for relation extraction and applying it to a support vector machine (SVM) are attracting attention. The characteristics of kernel-based methods in the field of relation extraction are that the performance of the kernel is best represented by constructing a kernel that best expresses the relationship between two entities in a sentence, and calculates the similarity between two relation-containing statements that includes it most effectively. It is very high.

The present invention proposes a method for improving relation extraction performance using lexical features based on PAS (Predicate-Argument Structure) pattern.

An object of the present invention is to provide a method for predicting a relationship by using a PAS pattern that significantly represents a relationship between entities existing in a sentence.

Another object of the present invention is to provide an apparatus suitable for the above method.

In order to achieve the above object, a method of identifying relationships between entities according to the present invention is

In the method of identifying a relationship between two entities in a sentence,

Analyzing a predicate-argument relationship of a sentence to obtain a PAS pattern representing a meaningful relationship between two entities in the sentence;

Generating a feature vector by referring to the extracted PAS pattern by using a predicate word, an argument word, a kind of predicate, and a relationship label between the predicate and the argument;

And inputting the feature vector into a machine learner to identify semantic relations between objects.

Here, the predicate-argument relationship of the sentence may be analyzed by using a parser using a head-driven structure structure grammar (HPSG).

In addition, the machine learning machine is characterized in that the RBF (Radias Basis Function) of the SVM (Support Vector Machine).

Apparatus for identifying a relationship between entities according to the present invention for achieving the above another object is

In the apparatus for identifying a relationship between two entities in a sentence,

A parser that analyzes the predicate-argument relationship of a statement and obtains a predicate-argument relationship graph connecting the two entities;

A PAS pattern extractor configured to extract a PAS representing a significant relationship between two entities existing in a sentence from the output of the parser to form a PAS pattern;

A feature vector generator for generating a feature vector using a predicate word and an argument word connected on the PAS pattern, a kind of predicate, and a relationship label between the predicate and the argument;

A relationship model learner for generating a relationship extraction model using the feature vectors; And

And a relationship predictor for predicting the relationship between the two entities using the feature vector generated from the relationship extraction model and the execution set.

The apparatus for recognizing a relationship according to the present invention further includes an object feature extractor for extracting important identification information of an object using unique property information of the object, wherein the feature vector generator includes the PAS pattern extractor and the object feature extractor. The final feature vector is constructed using the result of.

The relationship identification method and apparatus of the present invention uses a PAS structure expressing a significant relationship between each word present in a sentence using a predicate-argument relationship for each word constituting the sentence, as a feature vector. It has the effect of grasping the semantic relation between them.

Accordingly, the method and apparatus for identifying a relationship according to the present invention can be usefully used in high-level natural language processing applications such as information extraction, automatic summaries, and question and answer, in which the meaning of sentences plays a key role.

1 is a flowchart illustrating a relationship identification method according to the present invention.
2 shows an example of sentence analysis results using the Enju parser.
Figure 3 shows a predicate-argument relationship graph of each word obtained using the results provided by the Enju parser.
FIG. 4 illustrates a configuration of a pattern by extracting only PAS representing a meaningful relationship between two entities actually present in a sentence from the relationship graph shown in FIG. 3.
5 illustrates a configuration of the PAS-based relationship identification device developed in the present invention.

PAS is a structure that expresses a significant association between each word in a sentence using a predicate-argument relationship. In addition, the PAS pattern refers to an ordered sequence consisting of a minimum set of predicate-arguments that connect objects with important objects in a predicate-argument relationship graph for all words constituting the sentence.

Because of these characteristics, the PAS pattern becomes important feature information that expresses the association between two entities interacting within a sentence. Thus, relationship identification can be performed using the PAS pattern, which provides a semantic link from one entity to another.

1 is a flowchart illustrating a relationship identification method according to the present invention. Referring to FIG. 1, in the relation recognition method according to the present invention, a process of obtaining a predicate-argument relationship graph using a parser (s102), a process of obtaining a PAS pattern from a predicate-argument relationship graph (s104), and a feature vector from the PAS pattern Generating (S106) and identifying a semantic association between the entities using the feature vector (S108).

In step s102, a predicate-argument relationship graph is obtained by analyzing a predicate-argument relationship of a sentence. In the present invention, the sentence was analyzed using the Enju parser. The Enju parser is an HPSG parser developed by the Tsujii laboratory of the University of Tokyo's Computer Science.

2 shows an example of sentence analysis results using the Enju parser.

Referring to FIG. 2, the Enju parser receives a sentence as an input and analyzes and provides a predicate-argument relationship of each word constituting the sentence. The table below describes each field of the result of predicate-argument analysis.

Column number detailed description One predicate word 2 the basic form of a predicate word 3 parts of predicate words 4 Part-of-speech of the basic form of a predicate word 5 Position of predicate word in sentence 6  predicate types 7 Label of relationship between predicate and argument 8 argument word 9 argument base type 10 argument The part of speech of the word 11 argument The part-of-speech of the base type of the word 12 Position of word argument in sentence

Referring to the second and third row of FIG. 2, which is an analysis result of the sentence “Radon_exposure is the second leading cause of lung_cancer in the general population.” It has arguments 1 and 2 as verbs, of which argument 1 refers to the noun word radon_exposure and argument 2 refers to the other noun word cause.

The first line of the analysis simply expresses the root predicate of the statement, and the fourth line can be interpreted in the same way as the second and third lines.

Figure 3 shows a predicate-argument relationship graph of each word obtained using the results provided by the Enju parser.

In step s104, the PAS pattern is constructed by extracting only the PAS representing a meaningful relationship between two entities in the sentence from the predicate-argument relationship graph.

FIG. 4 illustrates a configuration of a pattern by extracting only PAS representing a meaningful relationship between two entities actually present in a sentence from the relationship graph shown in FIG. 3. Referring to FIG. 4, the linking of the arrows means that the predicate-argument relationship can be tracked from one entity to another interacting entity.

Therefore, if we trace the relationship between radon_exposure and lung_cancer, we can see that the relationship is formed based on an important lexical pattern such as is cause of. Again, this pattern can be used as an important feature in identifying interactions between two entities.

As a result, the relationship between entity 1 and entity 2 can be identified by the PAS pattern connecting the two entities in a meaningful relationship.

Therefore, by constructing a set of patterns that appear for each relationship and using the set of patterns as a basis for relationship prediction, it can be used for a relationship extraction system that extracts relationships between objects.

In step s106, feature vectors for machine learning are generated from the PAS pattern. In order to use the PAS pattern as a lexical feature, the present invention uses a predicate-argument structure, that is, a vector value using a predicate word, an argument word connected by an arrow in FIG. 4, a kind of predicate, and a relation label between the predicate and the argument. Generated.

In step s108, machine learning is performed using the generated feature vector to perform relationship identification. In the present invention, relationship identification was performed using the Radial Basis Function (RBF) kernel, which is one of the built-in kernels of the support vector machine (SVM).

5 illustrates a configuration of the PAS-based relationship identification device developed in the present invention. Referring to FIG. 5, the PAS-based relationship identification apparatus according to the present invention includes an integrated feature processing module 100 and an SVM module 200.

The integrated feature processing module 100 used a parser (Parser, 104), a basal phrase recognizer (Chunker, 112), and a part-of-speech tag (POS-tagger, 114). In order to extract various types of language features, the basal recognizer 112 and the part of speech tagger 114 were independently developed and combined with the system, and the parser 104 introduced Enju Parser and implanted into the system.

The integrated feature processing module 100 generates feature vectors for machine learning using the language analysis tool developed as described above. The PAS pattern extractor 106 using the parser 104 analyzes a predicate-argument relationship of sentences and extracts a PAS pattern connecting two entities.

The object feature extractor 116 extracts important identification information of the object by using the characteristic information of the object. Using the results of the PAS pattern extractor 106 and the object feature extractor 116, the integrated feature processing module constructs the final feature vector. However, when the characteristic information of the entity does not exist in the learning set 102 or the execution set 110, the feature vector may be configured by the PAS pattern alone.

The feature vectors configured as described above are used as inputs of the relationship model learner 204 and the relationship predictor 208 using the built-in kernel 202 of the SVM module 200, which is a machine learning algorithm. The relationship model learner 204 generates a relationship extraction model 206 using the feature vectors generated from the training set, and the relationship predictor 208 generates the relationship extraction model 206 and the integrated feature processing module 100. Use the feature vectors to predict what the relationship between the two entities really is.

<Example>

In order to examine the possibility that the PAS pattern can be used as a useful feature of relationship prediction, the following experiments were conducted on the AIMed collection.

  First, a relationship identification experiment was performed on all PAS patterns that express meaningful relationships among individuals. The pattern targeted here included not only lexical patterns but also symbolic patterns such as parentheses and commas.

Second, experiments were conducted on only patterns containing verb phrases that best represented significant relationships among individuals. If a verb phrase is abstracted above a certain level, the verb phrase can be an important clue for identifying a relationship so that it becomes a kind of relationship.

The two experiments presented above were performed using libsvm, and the experimental results are shown in Table 2.

Option value Result value cost gamma accuracy All patterns 512.0 0.0078125 86.2478 Pattern containing verbs 8.0 0.5 87.1499

Through this embodiment, we found that the PAS pattern that connects two entities can be a very useful clue when extracting the relationship between entities. In addition, patterns containing key words such as verb phrases can contribute more to performance. It was confirmed that there is. Therefore, when developing a relationship extraction system, a better performance relationship extraction system can be developed by utilizing the results obtained through the present invention.

In the present invention, a relationship extraction system was developed using a PAS pattern expressing a meaningful relationship between entities in a sentence, and through experiments, it was proved that the PAS pattern could be used as an important feature for relationship extraction.

In the future, a study on a method of constructing a mixed kernel by combining the relationship discrimination power of the PAS pattern demonstrated in the present invention with other existing methods of utilizing features, for example, using the similarity of syntax trees, is required.

By combining the syntax tree technique using syntactic similarity and the PAS pattern technique using semantic similarity, we can develop a better relation extraction system.

100 ... Integrated Quality Processing Module 200 ... SVM Module
102 Learning Set 104 Parser
106 ... PAS Pattern Extractor 108 ... Feature Vector Generator
110.Run Set 112 ... Basic Recognizer
114 ... 116 ... Object Feature Extractor
202 Built-in kernel 204 Relationship model learner
206 Relationship Extraction Model 208 Relationship Predictor

Claims (5)

Analyzing a predicate-argument relationship of a sentence and extracting a PAS pattern representing a meaningful relationship between two entities in the sentence;
Generating a feature vector by referring to the extracted PAS pattern by using a predicate word, an argument word, a kind of predicate, and a relationship label between the predicate and the argument; And
And inputting the feature vector into a machine learner having a relationship extraction model constructed from a set of PAS patterns appearing for each relationship to identify semantic relations between entities.
The method of claim 1,
A relationship identification method comprising analyzing a predicate-argument relationship of a sentence using a parser using a head-driven structure structure gradient (HPSG).
The method of claim 1,
The machine learner is a relationship identification method, characterized in that the RBF (Radias Basis Function) of the SVM (Support Vector Machine).
A parser that analyzes the predicate-argument relationship of a statement and obtains a predicate-argument relationship graph connecting the two entities;
A PAS pattern extractor configured to extract a PAS representing a significant relationship between two entities existing in a sentence from the output of the parser to form a PAS pattern;
A lipid vector generator for generating a feature vector using a predicate word and an argument word connected on the PAS pattern, a kind of predicate, and a relationship label between the predicate and the argument;
From the set of PAS patterns appearing for each feature vector and relationship A relationship model learner for generating a relationship extraction model; And
And a relationship predictor for predicting a relationship between two entities using the feature vector generated from the relationship extraction model and the execution set.
5. The method of claim 4,
It further comprises an object feature extractor for extracting important identification information of the object using the unique characteristic information of the object,
Wherein the feature vector generator configures a final feature vector using the results of the PAS pattern extractor and the feature feature extractor.

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