KR101012504B1 - Method of extracting Triplets by searching dependency grammar setence tree - Google Patents

Abstract

The present invention relates to a method and system for automatically extracting information of a relation triple for constructing an ontology from sentences of grammatically correct evaluation sentences.

According to another aspect of the present invention, there is provided a method of automatically extracting a triple relationship tree by searching a dependency grammar syntax tree, the method comprising: a first step of parsing a target sentence to generate a dependency grammar syntax tree; A second step of preprocessing the generated dependent grammar syntax tree after the first step and converting the dependency grammar syntax tree into a form for relationship extraction; And a third step of automatically searching for the dependency grammar syntax tree converted in the second step in a postorder manner and automatically extracting the relation triple.

Dependency Grammar Syntax Tree, Relationship Triple

Description

Method of extracting triplets by searching dependency grammar setence tree}

The present invention relates to a method and system for automatically extracting information of a relation triple for constructing an ontology from sentences of grammatically correct evaluation sentences.

Until now, the lexico-syntactic pattern has been mainly used to extract the relation triple. This was first proposed in Marti Hearst's 1992 paper Automatic Acquisition of Hyponyms from Large Text Corpora. In other words, if various grammatical patterns are made and the form of a given sentence matches the defined pattern, the relation triple is extracted using the pattern.

For example, to extract a triple of the form <cat, ISA, dog> from the sentence "The cat is a dog", the ISA pattern "<argument 1> is a <argument 2>" is conventionally used. And apply it to each sentence. However, this method has two major problems.

First, "London, which has the biggest airport in England, is a city." Statements such as, cannot use this grammatical pattern to extract information. Even if you use a wildcard like *, there are too many words between "London" and "is" that make it impossible to filter properly.

Second, using this pattern, only triples of the form <argument 1, set relationship, argument 2> can be extracted. That is, the information on the mathematical relationship that additionally modifies the arguments 1 and 2 is lost.

The present invention has been devised to solve the above problems, and it is possible to automate a part of ontology construction work which is mostly operated manually, and to automatically reduce the cost and time, thereby automatically relying on search of the dependent grammar syntax tree. It is an object to provide a triple extraction method.

In order to achieve the above object, the automatic relation triple extraction method by searching the dependency grammar syntax tree according to the present invention,

A first step of parsing the target sentence to generate a dependent grammar syntax tree; A second step of preprocessing the generated dependent grammar syntax tree after the first step and converting the dependency grammar syntax tree into a form for relationship extraction; And a third step of automatically searching for the dependency grammar syntax tree converted in the second step in a postorder manner and automatically extracting the relation triple.

The first step may include generating a dependency grammar syntax tree using a dependency grammar parser.

The second step may include displaying and constructing a term in the target sentence using a predefined term dictionary, recognizing an entity name that may be given in the dependent grammar syntax tree, and the dependent grammar. If there are To-negatives and the same nouns in the syntax tree, the process of displaying them separately, the process of processing connected conjunctions in the dependent grammar syntax tree, and if there are relational pronouns in the dependent grammar syntax tree, the relation pronouns can be substituted. Searching for nouns, indicating the action to be used to group two or more relation triples together for the same action, and combining the negative or frequency information with the verb node it modifies.

Here, the process of processing the connection conjunction, when the parts of two words connected by the connection conjunction is the same, when the parts of the word is not a verb, characterized in that the two words are tied to a node of the grammar syntax tree dependent on the two words. do.

In addition, the process of processing the connected conjunctions, if the two parts of the word connected by the connected conjunctions is the same, and if the parts of the word is a verb, characterized in that if the verbs all have a subject and an object, the sentences are divided. .

In addition, the process of processing the connected conjunction, if the two parts of the word connected by the connected conjunction is the same part of speech, if the part of the word is a verb, only the first verb has a subject and if the following verb does not have a subject two verbs It is characterized by grouping into one node.

In addition, the process of processing the connected conjunction is, if the two parts of the word connected by the connected conjunction is the same part of speech, the part of the word is a verb, the first verb has both the subject and the object, the following verb If not, copy the subject, attach it to the lower verb, and divide the two sentences.

In addition, the process of searching for a noun that can substitute for the relative pronoun may be characterized by giving a link to a noun designated by the relative pronoun.

In addition, in the process of displaying the action, the action is a two node whose parts of speech are verbs, the subject and the object are connected to each other, and have one or more semantic relations, and a child node having one or more terms among the child nodes except the two nodes. If is present, the node is characterized by displaying as an Action.

In addition, by extracting the relationship triple by converting the verb of the node indicated by the action to the same name, and converting the expression of the triplet information into a structure that modifies the argument 1 or the argument 2 using the same name to convert two triple information into one triple information It is characterized by.

In the third step, each node in the dependent grammar syntax tree has three data structures: Reserved Term (hereinafter 'RT'), Reserved Clue (hereinafter 'RC') and Relation Queue (hereinafter 'RQ'). Holds only one term, the RC holds a string, and the RQ holds a list of Relation Blocks (where the Relation Block is a set of one or more relation triples).

According to the automatic relationship triple extraction method by searching the dependency grammar syntax tree according to the present invention as described above,

Significant time and cost savings can be achieved by automating much of the ontology building from common sentences. In addition, it has the effect of solving the long-distance problem (a problem that cannot extract the relation triples between words that are far apart in the sentence) when using the general grammatical pattern-based method.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention; In describing the present invention, detailed descriptions of related well-known functions or configurations are omitted in order not to obscure the gist of the present invention.

An object of the present invention is to extract a relational triple from a sentence that is correct in grammar and has solved all descriptive pronoun problems. The present invention is focused on the fact that there can be any relationship between words connected to each other in the dependent syntax grammar tree of a sentence, and extracts the relation triples by searching the dependent syntax grammar tree in a postorder manner. Such relationship triple extraction may be performed by a computer program containing an algorithm for performing the contents described herein, or may be performed by a computer using a recording medium containing the algorithm.

The relationship triple is divided into three elements: <argument 1, set relationship, and argument 2>. Arguments 1 and 2 are two related concepts, and the set relationship is the relationship between the arguments 1 and 2 It's kind.

Hereinafter, the <argument 1, the set relationship, the argument 2> is expressed as [arg1, rel, arg2], the argument 1 is expressed as 'arg1', the argument 2 is expressed as 'arg2', and the set relationship is expressed as 'rel'.

Given a target sentence, there are three major steps to extract the relation triples from the given sentence (see Figure 3):

First step; Parse the target statement to create a dependent grammar syntax tree.

Second step; The generated dependency grammar syntax tree is preprocessed and converted into a form for relationship extraction.

Third step; Automatically extract relation triples by searching the transformed dependent grammar syntax tree in a postorder fashion.

In the first step, the dependency grammar syntax tree is generated using the dependency grammar parser for triple information extraction by clearly identifying the mathematical relations between words (see 1. Parsing of FIG. 3).

In the second step, preprocessing is performed through the following seven processes (see 2. Preprocessing of FIG. 3).

1. Display and build the term

Display and build a term using a predefined term dictionary. Here, the term 'term' means that there is a concept corresponding to the ontology to be constructed. For example, in the case of 'James buys a company', 'James' and 'company' become terms.

2. Object Name Recognition

Recognize and display object names. Here, an entity name refers to an object that exists in real life, such as a person's name or an institution's name (e.g. 'James', 'Microsoft', etc.).

3. To-negative and noun

The To-negative and the same nouns are themselves marked as Actions and must be associated with other subjects, and they can have their own subjects and objects. Therefore, To-negative and same-named verbs are marked separately for consideration in the extraction of relations for this special treatment.

4. Connection Connection

Process the connection connection. This is because there is a case in which the connection is made with a connection, in the case of simple enumeration, and in the extracted relationship, the arguments 1 or 2 of the triples are shared. Also, when extracting a relationship, in case of enumeration type, the relationship is set by one verb, and the relationship setting is the same, but argument 1 or argument 2 can extract several other relationships, and they have to deal with them.

If a connection appears in a dependency, it is handled according to the following rules.

(1) When the parts of two connected words are the same and are not verbs: Combine the two nodes into one node of the dependent grammar syntax tree.

(2) When the parts of the two connected words are the same and are verbs:

a. When both verbs have a subject and an object: Truncate the sentence.

b. When the first verb only has a subject, and the later verb does not have a subject: When sharing a subject and sharing the object of the later verb, combine the two verbs into one node.

c. When the first verb holds both the subject and the object, and the later verb does not have the subject: Since two verbs share only the subject, copy and paste the subject into the lower verb and cut the two sentences.

5. Resolution of substitute pronouns

The problem of anaphora is solved for relative pronouns such as which and who to avoid problems in triple extraction. That is, they link to the nouns they refer to.

6. Display of Action

Action is the concept of ontology to be created and expresses the action or changing state of something. Action is used to group two or more relation triples for the same action.

Referring to FIG. 2, the first result (Result 1) means that Samsung held a seminar and also that Samsung held something in London, but it does not mean that Samsung held a seminar in London-that is, The results lose important content. This is because, although the two relationship triples actually describe the same behavior of Samsung, it is impossible to express that these two kinds of information describe the same behavior without using the concept of Action. Therefore, in the process of extracting the relationship, first, 'hold' is changed to 'Holding', which is a noun form, to express the action triplet to extract the relationship triple (Samsung, Process, Holding), and to use the two relationship triple as constraints of holding. The information of two triples is converted into one triple and expressed. (Result 2)

Here, the condition of the node to be expressed as Action is as follows: The part of the verb is a verb and basically the subject and the object are directly connected to each other and have one or more semantic relations. If there is a node with more than one term.

7. Indication of negation / frequency

Combine negative / frequency information with verb nodes that it modifies. This is because the information of negation / frequency greatly affects the semantic value of the relation triple extracted from the verb node that it modifies.

The extracting of the relation triple in the third step is performed in the following manner (see 3. Extracting Triplets in FIG. 3).

The dependency grammar syntax tree obtained through the preprocessing is searched in postorder to extract the relation triple. Each node has three data structures: Reserved Term (RT), Reserved Clue (RC), and Relation Queue (RQ). The Clue refers to all strings existing on a connection line connecting two terms having a relationship on a dependency syntax grammar tree. This is used to connect the information of the term or the relationship set at the bottom of the syntax tree with other information at the top of the syntax tree, respectively. In this case, RT can hold only one term, RC can hold a string, and RQ holds a list of relation blocks. A relation block refers to one or more sets of relation triples (arg1, rel, arg2), and the relation triples held by the relation block conceptually share the same arg1. Unless stated otherwise, adding a triple to the relation queue means making and inserting a relation block containing only one relation triple. Mark the first triple of the relation block RB as RB [1] and the second triple as RB [2]. (See Figure 4)

Represent the node currently being searched as T, the child node of the target node as C, the Term of any Node A as A [Term], RT as A [RT], RC as A [RC], and RQ as A [RQ]. lets do it. Then change the RT, RC and RQ of each node according to the following cases. The Final Relation Queue (FRQ) holds the final relation set.

The relation triple extraction is performed according to the rules described below.

Case 1. If the target node is Term

Case 1.1 If there are no children of the target node:

In order to transfer information to the parent node, the node's Term is put in RT (see Fig. 5).

Case 1.2 When Child of Target Node Exists

Case 1.2.1 When a target node is referenced by which, who, etc.

Copies the RT and RQ contents of the verb of the child.

Case 1.2.2 When the contents of RT and RQ of the target node's children are all empty

It is the case that there is no information transmitted from child node. Put the Term of the node in RT. (See Figure 6)

Case 1.2.3 When the contents of RT of children of target node is not empty

It is the case that the term to be used for establishing the relationship has been delivered from the child node, and it is necessary to set the relationship with the node currently being searched using this. For a child C whose contents of RT are not Empty, add the following relationship to T [RQ]: (see Figure 7).

In case 1.2.3.1, the position of T is before C: (T [Term], C [RC], C [RT])

If the position of C in front of Case 1.2.3.2 is before T: (C [RT], C [RC], T [Term])

Case 1.2.4 When RQ of Children of Target Node Is Not Empty

In this case, the term transmitted from the child node to establish the relationship with the target node has already been established with the other term. Therefore, it establishes a relationship between the target node and the delivered term, and gives a constraint on the established relationship using the contents of the delivered RQ.

For non-empty child C, add the following relationship to T [RQ]:

For each and every element t of C [RQ],

(T [Term], C [RC], RB [1] [arg1] and (RB [1] [rel] RB [1] [arg2]) and (RB [2] [rel] RB [2] [arg2 ]) and ...)

(Hereinafter, notation like (T [Term], C [RC], t [arg1] and (t [rel] t [arg2]) handles the constraint using all elements of each Relation Block as above. Means.)

In this case, RB [1] [arg1] is the term that has been passed, and (RB [1] [arg1], RB [1] [rel], RB [1] [arg2]), etc., have been set in advance. . (See Traverse 5 in Figure 8)

Case 2. If the target node is not a term

In this case, the target node itself does not have any information, and serves to convey information of the term located in the offspring, or to establish a relationship between the offspring.

Case 2.1 No Child of Target Node

There is no information from the child and no information to convey. Does nothing. (E.g. articles)

Case 2.2 When Child of Target Node Exists

Case 2.2.1 When the contents of RT and RQ of the target node's children are all empty

In this case, too, there is no information to be transmitted from the child and no information to be transmitted to the parent node exists. Does nothing too.

Case 2.2.2 The target node is the verb part or the same name of the To-negative

In this case, make the verb part of the target node into an Action, and the children connected to the target node into the newly created Action and Triple. It also makes all extracted relations into one relation block. Traverse 4 below shows that two triples are grouped into one relation block. (See Traverse 4 in Figure 9)

Case 2.2.3 A child node exists that has a dependency of its subject on the target node and is not an auxiliary verb

Case 2.2.3.1 A child node exists that has a dependency of an object on the target node

Case 2.2.3.1.1 When a target node is marked as an Action node

In this case, at least one node whose RT or RQ is not Empty among the children by the Action node indication criterion necessarily exists. In this case, two or more relation triples are calculated by the general method, and it is difficult to indicate the association between the triples. Instead, the target node is made into an action and the relations are expressed in the form of a formula for the target action. In other words, the verb is transformed into Action form and the subject is connected in Process, and the object and information of other children are added as constraints. To do this, perform the following steps.

For each child node C whose RT or RQ is not Empty, add the following to T [RQ]:

If the child node having the dependency of the subject is S and the child node having the dependency of the object is O, for each to (Triple of Object) in O [RQ] and tc (Triple of Child) in C [RQ] ,

a. (S [RT], Process, T [Term] (in Noun Form) AND (Objective O [Term]) AND (C [Clue] C [Term])) (See Traverse 6 of FIG. 10)

b. (S [RT], Process, T [Term] (in Noun Form) AND (Objective to [arg1] and (to [rel] to [arg2])) AND (C [Clue] C [Term])) 11 see Traverse 8)

c. (S [RT], Process, T [Term] (in Noun Form) AND (Objective O [Term]) AND (C [Clue] tc [arg1] and (tc [rel] tc [arg2])) See Traverse 8)

d. (S [RT], Process, T [Term] (in Noun Form) AND (Objective to [arg1] and (to [rel] to [arg2])) AND (C [Clue] tc [arg1] and (tc [ rel] tc [arg2]))) (see Traverse 10 in FIG. 13)

Case 2.2.3.1.2 If the target node is not an Action node

In this case, simply set the relationship between the subject and the object.

Case 2.2.3.1.2.1 If the extracted relationship is isA

If a node's RQ is not empty, that node is being modified by something. When a node that is modified by an isA relationship and an unqualified node are bound, it is obvious that the node that is modified in the classification system becomes a child of an unmodified node. That is, the unqualified side, that is, the side where RQ is Empty becomes 'arg1', and the side receiving the modifier, that is, the side where RQ is not empty, becomes 'arg2'. If neither node is modified, it naturally takes the form A is a B so that the subject is placed in place of arg1 and the object in arg2.

In order to actually show this, the following relationship establishing procedure is established (see Traverse 6 of FIG. 14).

If S [RQ] is empty, if O [RQ] is empty, add (S [RT], isA, O [RT]), or (S [for each triple to of O [RQ]). RT], isA, to [arg1]) and (S [RT], to [set relation], to [arg2]) are added to T [RQ].

If S [RQ] is not empty, then (O [RT], isA, ts [arg1]) and (O [RT], ts [rel], ts [arg2) for each triple ts of S [RQ]. ]) Is added to T [RQ]. (See Traverse 6 in FIG. 15)

Case 2.2.3.1.2.2 If the extracted relationship is not isA

In this case, simply establish the relationship between the subject and the object. At this point, clue simply sets it between the subject and the object in the dependency syntax tree. (See Figure 16)

Add the following to T [RQ]:

(S [RT], S [RC] + T [term] + O [RC], O [RT]) (+ means String Concatenation.)

For each to (Triple of Object) in O [RQ],

(S [RT], S [RC] + T [term] + O [RC], to [arg1] AND (to [rel] to [arg2]))

Case 2.2.3.2 When a target node does not have a child node with object dependencies

In this case, RT and RQ do not need to be empty but have relations with child nodes.

Case 2.2.3.2.1 If the extracted relationship is isA, the processing is the same as Case 2.2.3.1.2.1.

In the characteristic of the relationship of isA, the following is true.

If S [RQ] is empty, if C [RQ] is empty then (S [RT], isA, C [RT]), or for each triple tc of C [RQ] (S [RT] , isA, tc [arg1]) and (S [RT] .tc [rel], tc [arg2]) are added to T [RQ].

If S [RQ] is not empty, then (C [RT], isA, ts [arg1]) and (C [RT], ts [rel], ts [arg2) for each triple ts of S [RQ]. ]) Is added to T [RQ].

Case 2.2.3.2.2 If the extracted relationship is not isA, the processing is the same as in Case 2.2.3.1.2.2.

For children C of the target node whose RT or RQ is not empty, (S [RT], S [RC] + T [term] + C [RC], C [RT]) is set to T [RQ]. In addition, and also for each triple tc of C [RQ] (S [RT], S [RC] + T [term] + C [RC], tc [arg1] AND (tc [rel] tc [arg2) ])) Is added to T [RQ].

Case 2.2.4 A child node with subject dependencies does not exist in the target node or is an auxiliary verb

In this case, one child usually has contents in RT and RQ. Copies the contents of this child and adds the contents of the target node to clue. If the target node comes before the child node, add clue to the front. If it comes after, add clue to the back. This is usually the case with prepositions such as in or for.

Cases described above will be described with reference to FIG. 3.

In the example of FIG. 3, this is the process performed in 3. Extracting Triplets. The first node to look at by post-order traversing is "James". According to Case 1.1, the RT of the James ◎ node becomes James. The node "a" retrieved afterwards corresponds to case 2.1. It does nothing. The node "which" retrieved afterwards is a relative pronoun. Copies ("company") to its own RT, since the search for "has" is an auxiliary verb, so RT is "company" and RC is "has" by case 2.2.4. The same applies to node "London": case 2.2.4 applies to node "in", case 2.2.3.1.1 applies to node "hold", which is searched for the eighth node, and to node 9 " case "is applied to" company "and ◎ case 2.2.3.1.2.2 is applied to the last node" visit "to get the final result.

As described above, the automatic relation triple extraction method by searching the dependency grammar syntax tree according to the present invention has been described with reference to the drawings, but the present invention is not limited by the embodiments and the drawings disclosed herein, and the present invention. Of course, various modifications can be made by those skilled in the art within the scope of the technical idea.

1 is a flow chart illustrating a relation triple extraction order according to the present invention.

2 is an example of triple extraction when the concept of Action is used and when it is not used.

3 is an example of the overall relationship extraction process.

4 is a table illustrating definitions of words used in a relationship extraction process.

5 is an illustration of case 1.1 of a rule.

6 is an illustration of case 1.2.2 of the rule.

7 is an illustration of case 1.2.3 of the rule.

8 is an illustration of case 1.2.4 of the rule.

9 is an illustration of case 2.2.2 of a rule.

10 is an example of a of case 2.2.3.1.1 of a rule.

11 is an example of b of case 2.2.3.1.1 of a rule.

12 is an example of c of case 2.2.3.1.1 of a rule.

13 is an example of d of case 2.2.3.1.1 of a rule.

14 shows an example in which the RQ of the subject is empty in case 2.2.3.1.2.1 of the rule.

FIG. 15 shows an example in which the RQ of the object is empty in case 2.2.3.1.2.1 of the rule.

16 is an illustration of case 2.2.3.1.2.2 of the rule.

Claims (11)

A first step of parsing the target sentence to generate a dependent grammar syntax tree; A second step of preprocessing the generated dependent grammar syntax tree after the first step and converting the dependency grammar syntax tree into a form for relationship extraction; And, A third step of automatically searching for the dependent triplet syntax tree converted in the second step in a postorder manner and automatically extracting the relation triple Automatic relationship triple extraction method by searching the dependency grammar syntax tree comprising a. The method according to claim 1, The first step is an automatic relationship triple extraction method of searching a dependency grammar syntax tree using a dependency grammar parser. The method of claim 1, wherein the second step, Displaying and constructing a term in the target sentence using a predefined term dictionary; Recognizing a subject name that can be given in the dependent syntax syntax tree; If there is a To-negative and the same name in the dependency grammar syntax tree, the process of displaying it separately, Process of connecting conjunctions in the dependent grammar syntax tree, Searching for a noun that can substitute for a relative pronoun when there is a relative pronoun in the dependent grammar syntax tree, Displaying the Action to use to group two or more relation triples together for the same action, The process of combining negative or frequency information with the verb node it modifies Automatic relation triple extraction method by searching the dependency grammar syntax tree comprising a. The method according to claim 3, The process of processing the connected conjunction is characterized in that when the parts of two words connected to the connected conjunction are the same parts of speech and the part of the word is not a verb, the two words are bound by one node of the grammar syntax tree. Automatic relation triple extraction method by searching grammar syntax tree. The method according to claim 3, The process of processing the connected conjunction is, if the two parts of the word connected by the connected conjunction is the same part of speech, if the part of the word is a verb, the dependent grammar, characterized in that if the verbs have both the subject and the object, the sentence is divided A method of extracting automatic relation triples by searching the syntax tree. The method according to claim 3, The process of processing the conjunctive adjunct includes two parts of the verb connected to the conjunctive adjunct, and if the part of the word is a verb, only the first verb is given and the second verb does not have a subject. Automatic triple extraction method by searching dependent grammar syntax tree characterized by grouping by node. The method according to claim 3, The process of processing the conjunctive adjunct is that if the part of speech of two words connected with the conjunctive adjunct is the same and the part of the word is a verb, the first verb holds both the subject and the object, and the later verb does not have the subject. If not, the automatic relation triple extraction method by searching the dependent grammar syntax tree characterized by copying the subject, appending it to the lower verb, and dividing the two sentences. The method according to claim 3, The process of searching for a noun that can substitute for the relative pronoun is an automatic relation triple extraction method by searching for a dependency grammar syntax tree characterized by linking to a noun designated by the relative pronoun. The method according to claim 3, In the process of displaying the action, the action is two nodes in which the part-of-speech is a verb, and the subject and the object are connected to each other and have one or more semantic relations, and there is a child node having one or more terms among the child nodes except the two nodes. If it is, the automatic relationship triple extraction method by searching the dependency grammar syntax tree characterized in that the node is represented as an Action. The method according to claim 9, Converts the verb of the node indicated by the action into a same name verb, extracts a relation triple, and converts two triple information into one triple information by converting the expression triple into a structure that modifies the argument 1 or the argument 2 using the same name. Automatic relation triple extraction by searching dependent syntax syntax tree. The method according to claim 1, In the third step, each node in the dependent grammar syntax tree has three data structures: Reserved Term (RT), Reserved Clue (RC), and Relation Queue (hereinafter RQ). Only, where RC holds a string, and RQ holds a list of Relation Blocks (where Relation Block is a set of one or more relation triples). Relationship triple extraction method.

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