KR100736754B1 - Method for investigating citation relations using spanning tree - Google Patents

Abstract

A citation relationship search method using a minimum spanning tree showing a citation relationship of a patent in three dimensions with perspective and angle. The citation relationship information of a plurality of technical document data and citation relationship information input from the server And a conversion system for converting a citation relationship into a citation relationship, wherein the conversion system requests the server for citation relationship investigation for a specific technical document, and the conversion system converts citation relationship information of the technical document inspected and sent by the server. Receiving, the transformation system tracking the minimum spanning tree using the received citation relationship information, and the transformation system two dimensions of each node of the tracked minimum spanning tree in the x-axis and y-axis planes. And the transform system outputs a z-axis at each node of the minimum spanning tree. This stage, the conversion system for computing the coordinates of the statistical information includes the step of outputting a 3-D relationship is also incorporated with a perspective angle and a combination of the x, y, z-axis value.

By using the above-described citation relationship investigation method using the spanning tree, the citation relationship between patents can be easily identified by showing the citation relationship of the patent in three dimensions having a perspective and an angle.

 Spanning Tree, Citations, Citations, Citations, Station

Description

Citation relationship investigation using spanning tree {METHOD FOR INVESTIGATING CITATION RELATIONS USING SPANNING TREE}

1 is a block diagram illustrating a system for examining a citation relationship diagram using a spanning tree according to the present invention;

2 is a flowchart for explaining a method of examining a citation relationship diagram according to an embodiment of the present invention;

3 is a graph showing an embodiment of a three-dimensional citation relationship diagram using a spanning tree according to the present invention;

4 is a view showing an embodiment of a citation relationship between technical documents according to the present invention;

5 is a diagram illustrating a process of tracking a minimum spanning tree according to the present invention;

6 is a view showing an embodiment of a spring model according to the present invention,

7 is a diagram illustrating a method of outputting a three-dimensional citation relationship diagram according to a point of view of the present invention;

8 is a view illustrating various views of a three-dimensional citation relationship diagram according to a user's viewpoint in accordance with the present invention.

Explanation of symbols on the main parts of the drawings

10: conversion system 20: server

101: coordinate means 102: storage means

201: investigation means 202: transmission means

203: database

The present invention relates to a citation relationship diagram, and more particularly, to a citation relationship investigation method using a minimum spanning tree that shows the citation relationship of a patent in three dimensions with perspective and angle.

In general, when conducting a prior patent technology search using a patent database, terms representing technical contents, patent classifications, or unique codes of the database are frequently used. As the technology advances, the terminology continues to change, and if the term is currently used, the original basic patent may not be searched. In addition, only old patents may be searched, and recently applied patents may not be searched. In this way, if a user selects a term, a classification, a code, or the like used in a search, a desired patent cannot be found. In addition, when searching using the applicant's name, if the organization name is changed, the search should be performed using the new organization name. Therefore, using the citation of the patent it is easier to find the desired patent.

The patent specification lists cited documents and cited patents citing prior art. This list is the literature and patents cited to represent past patents and is referred to as cited in terms of the patents to be investigated. Many patent databases contain these citations, which can be used to infer the importance of each patent. These citations can also be referred to in patent publications and the like. Older data can be found by reversing the cited material.

In contrast, in terms of citations, the invention to be investigated is referred to as a citing patent, and the patent to be investigated is filed more recently than the publication of references. These cited patents are difficult to investigate only by referring to the patent specification, but can be searched relatively simply in a search using a database. In addition, if the number of citations in the cited patent is confirmed in the same form as the citation, it can be used for evaluation of each patent.

This citation and citation information can be used to obtain a very large amount of information by identifying related patents and literature descriptions, and to investigate in depth technically relevant patents, even if the terminology changes as the technology advances. Can be. In addition, the examination of cited patents may be utilized as a preliminary investigation before filing a patent.

One of the methods of analyzing the correlation between each registered patent for patent analysis is a method of visually showing the correlation between the cited patents and showing them visually. For example, use the citation relationship between the cited patents related to the patent to be investigated to determine the importance of the technology by investigating which patent is the basic patent in a particular technology and which citations are cited the most among the related patents. Will be done. This is similar to evaluating the value of a paper according to the citation status of references cited in each article in the paper.

In addition to examining such basic patents and important patents, cited patents are also effectively used to examine related invalid evidence data of patents. For example, it is useful to find similar invalid reference materials by intensively examining what patents are related to US family patents and which patents are cited again. can do.

You can also find out how your patent is being cited to others who have filed it later. This may be used as a judgment data about the use of my patent, problems between inventions, or licensing.

An example of a visual presentation method of such a search result is disclosed in Japanese Patent Laid-Open No. 2004-355286 (a search result presentation method, apparatus and program).

According to the technique disclosed in the above publication, in each search result using a plurality of search terms, the frequency of occurrence of each search term is acquired, a metering is calculated based on the frequency of appearance of each search term, and the three-dimensional space is searched based on the frequency of appearance of the desired search term. Set the scale unit weighing for each display axis, determine the coordinate position in the three-dimensional space of each search result based on this set scale unit weigh, and arrange and present each search result in the three-dimensional space of this coordinate position A method, apparatus and program for presenting search results are disclosed.

Moreover, an example of the apparatus which visually showed the mutual relationship of technical documents is disclosed by Unexamined-Japanese-Patent No. 2004-348771 (technical document retrieval apparatus).

The technique disclosed in the above publication is a technical document retrieval apparatus for retrieving a technical document such as a patent document or a technical paper, comprising: a retrieving means and related document extracting means for extracting information of a reference document cited in the technical document; The related document extracting means extracts information of a reference document cited as the underlying technical document, and the searching means searches for a technical document corresponding to the reference document extracted by the related document extracting means, and the retrieved technical document Disclosed is a technical document retrieval apparatus which extracts information of a reference document cited by the related document extraction means, repeats this operation, and displays the relationship of each technical document to be retrieved so as to visually know.

However, the conventional patent citation relationship diagram is in the form of a two-dimensional tree, a graph, etc. Since the information of the patent corresponding to each node is expressed in letters or colors, it is not easy to grasp the overall information and compare the patents. In the case of a large number of patents included, the connection lines are complicated, making it difficult to identify the citation relationship between patents, or the entire citation relationship information cannot be viewed as a selective output of the connection line for the whole citation relationship.

Also, in Publication No. 2004-355286, the search results are shown in three dimensions, but based on the frequency of occurrence of search terms, there is a problem that is insufficient to investigate the citation relationship between the patents, basic patents, important patents, and the like.

In the above-mentioned publication No. 2004-348771, although the interrelationships of technical documents are shown in three dimensions, they are expressed in a simple and single form of three dimensions, and do not show a significant difference in quantification. There was a problem that was difficult to optimize.

An object of the present invention is to solve the problems as described above, to provide a citation relationship investigation method using a spanning tree showing the citation relationship of the patent in three dimensions having a perspective and an angle so as to easily identify the citation relationship between the patents It is.

Another object of the present invention is to provide a citation relationship research method using a spanning tree showing a citation relationship diagram at a point in time desired by a user without losing citation relationship information.

It is another object of the present invention to provide a citation relationship investigation method using a spanning tree that can be effectively used to grasp the citation relationship between patents more effectively, the use of patents, pre-application preliminary examination, reference patents and important patents, licensing will be.

In order to achieve the above object, a citation relationship research method using a spanning tree according to the present invention includes a server for examining citation relationship information of a plurality of technical document data and a conversion system for converting citation relationship information input from the server into citation relationship. In the citation relationship investigation method comprising the step of the conversion system to request the citation relationship investigation for a specific technical document to the server, the conversion system receives the citation relationship information of the technical document sent out by the server is investigated The tracking system tracks the minimum spanning tree using the received citation information, and the transformation system arranges each node of the tracked minimum spanning tree in two dimensions on the x and y axis planes. The statistical system to output the z-axis output from each node of the minimum spanning tree Calculating coordinates of the coordinates; and outputting a three-dimensional citation relationship diagram having perspective and angle by combining the values of the x, y, and z axes, and the conversion system outputs the z-axis. When the information is changed, the 3D citation relationship diagram may be output by reflecting the changed value.

In the citation relationship investigation method using the spanning tree according to the present invention, the step of tracking the minimum spanning tree by using the citation relationship information examined by the conversion system may include: the citation relationship information examined by the conversion system; Calculating a common citation factor for the step, wherein the conversion system constructs a graph of citation relationships using the calculated common citation factor as a weight of citation relationship, and the conversion system calculates a minimum spanning tree from the created graph. And tracing.

Further, in the citation relationship investigation method using the spanning tree according to the present invention, the step of placing each node of the tracked minimum spanning tree in two dimensions on the x-axis and y-axis plane in the transformation system is the elastic force between each node to be arranged By applying a spring model using the repulsive force is characterized in that the arrangement on the x-axis and y-axis plane.

In addition, in the citation relationship investigation method using a spanning tree according to the present invention, the three-dimensional citation relationship diagram is characterized in that it can be output by moving horizontally or rotationally depending on the coordinates and angles of the viewpoint selected by the user. It is done.

In addition, in the citation relationship investigation method using the spanning tree according to the present invention, the citation relationship diagram is the minimum spanning tree, the entire citation relationship outputting all connection lines according to the user's selection, and all the connection line highlighting the minimum spanning tree Characterized in that the output can be printed with the entire citation relationship.

In addition, according to the present invention, a method for searching a citation relationship using a spanning tree may include storing all of the citation relationship diagram or some technical documents selected by a user.

In addition, the method for searching a citation relationship using a spanning tree according to the present invention is characterized in that the entire citation relationship diagram or a part shown on the screen can be converted into an image file and stored.

Before describing the present invention, some terms used in the present invention will be described.

The citation relationship between nodes in the technical document is complicated, and when it is expressed in graph, it is difficult to grasp the citation relationship between the entire citation relationship and each technical document. Therefore, it is necessary to remove a part of the citation relationship. In other words, since the citation relationship between nodes in the technical document is complicated, part of the citation relationship should be removed, and the spanning tree is used.

First, a spanning tree refers to a tree connecting all vertices of G among subgraphs of a specific graph G. In other words, the spanning tree is the minimum subgraph that contains all the vertices of the graph and is connected.

When the edges of the spanning tree are weighted, the smallest spanning tree of the sum of the weights is called the minimum spanning tree and is also called the minimum cost extension tree. The minimum spanning tree contains only the corners that originally existed in the graph, and contains only n-1 edges when the number of vertices is n, and there should be no cycle.

Hereinafter, the most preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily practice the present invention. . In addition, in description of this invention, the same code | symbol is attached | subjected to the same part and the repeated description is abbreviate | omitted.

1 is a block diagram illustrating a system for examining a citation relationship diagram using a spanning tree according to the present invention.

As shown in FIG. 1, a system for visualizing a citation relationship diagram using a spanning tree may be used by a user who wants to know citation relationship information of a specific technical document to connect to a network and request citation relationship information. And a server 20 connected to the conversion system 10 through a network and checking the citation relationship of the technical document data according to a request input from the conversion system 10. The conversion system 10 is a conventional computer system and is provided with input / output means, such as a printer, a monitor, a keyboard, and a mouse.

In addition, in FIG. 1, the conversion system 10 receives the citation relationship information irradiated from the server 20 and converts the coordinates to be output to the citation relationship diagram. Storage means 102 for storing data,

The server 20 is a search means 201 for examining the citation relationship information of the technical document data, a sending means 202 for transmitting the examined citation relationship information to the conversion system 10, and a database 203 for storing the technical document data. ).

Next, a method of storing condition information according to an embodiment of the present invention will be described with reference to FIGS. 2 to 8.

2 is a flowchart illustrating a method of examining a citation relationship diagram according to the present invention, and FIG. 3 is a graph showing an embodiment of a three-dimensional citation relationship diagram using a spanning tree according to the present invention.

First, as shown in FIG. 2, the user connects to the server 20 using the conversion system 10 to check the citation relationship (ST 2010). In this case, the server 20 performs a member authentication procedure to check whether the member is available using a known technology in the art. If it is confirmed that the member is not a usable member in the authentication procedure, a registration procedure for converting to a usable member using a known technology in the art is performed. Member authentication and joining procedures are well-known techniques commonly used in the art, so detailed descriptions are omitted.

Next, the conversion system 10 requests the server 20 to examine the citation relationship for a specific technical document (ST 2020), and receives the citation relationship information of the technical document examined and sent by the server. That is, upon request, the search means 201 of the server 20 searches the database 203 for citation relationship information of the requested technical document and examines it (ST 2030), and converts the examined citation relationship information to the conversion system 10. Is sent (ST 2031), and the conversion system 10 receives it (ST 2032).

Coordinates to be output on the x, y, and z axes are obtained using the citation relationship information received from the coordinate means 101 of the conversion system 10. First, a common citation coefficient is calculated for each received citation relationship information to obtain coordinates of the x and y axes (ST 2040). The calculation method for the common citation coefficient will be described later with reference to FIG. 4. The calculated common citation coefficient is calculated as (1-common citation coefficient) to create a graph of the citation relationship with the weight of the citation relationship (ST 2050), and then the minimum spanning tree is traced from the created graph (ST 2060). The method of tracking the minimum spanning tree will be described later with reference to FIG. 5. Each node of the traced minimum spanning tree is applied to the spring model and placed in two dimensions on the x and y axis planes (ST 2070) to create a two-dimensional minimum spanning tree rooted in the technical document to be investigated. . A method of arranging the x-axis and the y-axis by applying a spring model will be described later with reference to FIG. 6.

Next, the coordinates of the statistical information, such as the reference number or the referenced number to be output on the z-axis at each node of the minimum spanning tree are calculated (ST 2080). The information to be printed on the z-axis uses the values of the preset items as default values, and the item values can be changed by the user even after the citation relationship is completed and printed. By combining the calculated values of the z-axis and the values of the x- and y-axes arranged in two dimensions, a three-dimensional citation relationship diagram having perspective and angle as shown in FIG. 3 is output (ST 2090). The output citation relationship diagram is displayed in the form of a 3D citation relationship graph.

As shown in FIG. 3, the output citation relationship outputs the minimum spanning tree (FIG. 3A), the total citation relationship outputting all the connection lines (FIG. 3B), and all the connection lines in which the minimum spanning tree portion is highlighted. It can be output as a full citation relationship (Fig. 3c). At this time, the output is in the reverse order of the z coordinate.

The output 3D citation relationship diagram may be output by horizontally or rotationally moving according to the coordinates and angles of the viewpoint selected by the user. In other words, the user can be regarded as viewing the tree at a specific angle at a specific position in the three-dimensional space. When a viewpoint change is input to the conversion system 10 (ST 2100), it is checked whether it is horizontal movement (ST 2101). The viewpoint change is input by dragging the mouse. If the horizontal movement, the coordinate means 101 calculates the difference between the current coordinate and the previous coordinate to change the values of the x and y axes by the size of the x component and the size of the y component (ST 2102). The values of the x and y axes are updated with the changed values (ST 2104), and the 3D citation relationship diagram is output again using the updated values (ST 2090). The output citation relationship diagram is displayed in the form of a 3D citation relationship graph.

If it is determined in step ST 2101 that the movement is not horizontal, it may be determined that the movement is rotation. Accordingly, the coordinate means 101 obtains the difference between the current coordinates and the previous coordinates, and changes θ by the size of the x component and φ by the size of the y component (ST 2103). The values of the x and y axes are updated with the changed values (ST 2104), and the 3D citation relationship diagram is output again using the updated values (ST 2090). The output citation relationship diagram is displayed in the form of a 3D citation relationship graph. A method of horizontally moving or rotatingly moving according to the user's viewpoint will be described later with reference to FIGS. 7 and 8.

Also, the information to be output on the z-axis in the output 3D citation relationship diagram may be selectively set by the user. That is, when a z-axis change request is input to the conversion system 10 (ST 2110), the coordinate means 101 updates the z-axis value using the input z-axis value (ST 2104), and then updates the updated value. The 3D citation relationship diagram is output again (ST 2090). The output citation relationship diagram is displayed in the form of a 3D citation relationship graph.

In addition, when an image file storage request is input to the conversion system 10 (ST 2120), the entire cited relation diagram or the part shown on the screen is converted into an image file such as jpg and stored in the storage means 102 (ST 2121). When the technical document storage request is input to the conversion system 10 (ST 2130), the entire technical document of the citation relationship diagram or the partial technical document selected by the user is stored in the storage means 102 (ST 2131).

In addition, a toolbar is provided to enable zooming / reducing, grouping of applicants / IPCs, selecting 1-dimensional statistical information, and viewing patent DOCs, expanding child nodes, closing extended child nodes, and deleting nodes. The same application function, such as a display function, is provided in the form of a popup.

After all the work is completed, if a request to store the investigation result is input to the conversion system 10 (ST 2140), the investigation result is stored in the storage means 102 (ST 2141).

The arrangement of citations between technical documents in two dimensions on the x-axis and y-axis planes using the minimum spanning tree will be described with reference to FIGS. 4 to 6.

4 is a diagram illustrating an embodiment of a citation relationship between technical documents according to the present invention.

The citation relation between nodes of technical documents is complicated and it is difficult to grasp the whole citation relation and citation relation between each technical documents when expressed in graph, so that users can grasp the entire overview visually by emphasizing important connection relation among citation relations. I need to work. Use the minimum spanning tree for this task.

Spanning tree is a subgraph having a tree structure in which all nodes are connected in a graph structure, and a minimum spanning tree is a spanning tree in which the sum of weight values of the connections is minimum. It is known that applying this minimum spanning tree to the citation relationship diagram preserves much of the citation relationship of the citation relationship diagram with a relatively small amount of computation. A citation relationship refers to a citation relationship such as a hub that quotes many nodes and an authority that is a node quoted by a large number of nodes.

The common citation factor, which is the similarity of the two technical documents in the citation relationship, can be calculated as follows (ST 2040).

식(1)

Formula (1)

In equation (1), c (d _i ) is the number of times the document d _i is cited by another document, and cc (d _i , d _j ) is the number of times the documents d _i and d _j are cited simultaneously by the same document. , sim (d _i , d _j ) is the common citation factor of d _i and d _j . The common citation coefficient is a kind of normalized co-citation coefficient.

For example, suppose document A is cited by documents C, D, E, F, G, and document B is cited by C, D, F, H, I, as shown in FIG. ) = 5, c (B) = 5, cc (A, B) = 3, it is calculated as follows.

In order to include the high similarity citation relationship in the spanning tree, the actual minimum spanning tree algorithm creates a graph of the citation relationship using 1-sim (di, dj) as the weight of the citation relationship (ST 2050).

5 is a diagram illustrating a process of tracking a minimum spanning tree according to the present invention.

As shown in FIG. 5, after selecting an arbitrary node from the graph created in step ST 2050, the smallest weight among the connections between the tree configured in each step and the nodes not included in the tree is connected and included in the tree. Trace the minimum spanning tree (ST 2060).

The process of tracing the minimum spanning tree shown in FIG. 5 is by the Prim algorithm. Prim algorithm is performed by the following process.

First, select any node and add it to the spanning tree.

Next, find the minimum weight among the edges connecting nodes included in the spanning tree and nodes not included in the spanning tree, and add the edges and nodes not included in the spanning tree to the spanning tree. Repeat this (total number of nodes minus 1).

For example, if there are seven nodes, first select any node and add it to the spanning tree, and then repeat six times to find and add the minimum weight among the edges connecting the spanning tree and the remaining nodes.

6 is a view showing an embodiment of a spring model according to the present invention.

The layout of the minimum spanning tree is a two-dimensional layout of each node of the spanning tree on the x- and y-axis planes by applying a spring model that visualizes the relationship using elastic and repulsive forces (ST 2070). ), Create a two-dimensional minimum spanning tree rooted at the technical documents to be examined.

At this time, after arranging the nodes so that the links do not overlap in time order, the force applied to each node is calculated until the position variation of each node is less than or equal to a threshold value, and the nodes are recomputed accordingly. Repeat that.

The elastic force and the repulsive force applied to each node can be calculated as follows. In formulas (2) and (3), C _si , C _d , and C _ri are positive constants, and V _i is a set of nodes connected to node i.

The spring force of node i

식(2)

Formula (2)

Repulsive force received by node i

식(3)

Formula (3)

As shown in FIG. 6, the elastic energy F _s of the deformed spring tries to maintain the length between the two nodes, and the repulsive force F _r is applied between the nodes to push in the opposite directions.

The 3D citation relationship diagram is converted and output according to the viewpoint of the user, according to FIGS. 7 and 8.

7 is a diagram illustrating a method of outputting a three-dimensional citation relationship diagram according to an embodiment of the present invention.

As shown in FIG. 7, the 3D citation relationship diagram output in step ST 2090 may be output by horizontally moving or rotatingly moving according to the coordinates and angles of the viewpoint selected by the user.

To output the citation tree in three-dimensional space according to the viewpoint, initialize the three-dimensional position coordinates (tx, ty, tz) and the angle information (θ, φ) of the line of sight of the user's viewpoint information, and then terminate the program. Repeatedly converting and outputting the node, link coordinates and statistical coordinates of the tree.

Converting and outputting node, link coordinates and statistical coordinates of the tree are as follows. First, translate to (-t _x , -t _y , -t _z ) (FIG. 7A), rotate by -θ perpendicular to the z-axis (FIG. 7B), and rotate by -φ perpendicular to the x-axis. (FIG. 7C).

Next, we apply perspective transformation to express perspective. Z _min is the minimum value from the user's point of view to the viewing volume.

Finally, draw the (x '', y '') coordinates in large order by sorting them in the z '' component of the transformed coordinates.

8 is a view illustrating various views of a three-dimensional citation relationship diagram according to a user's viewpoint according to the present invention.

As shown in Fig. 8, in the case of viewpoint rotation (Fig. 8A), the difference between the current coordinate and the previous coordinate of the pointer indicating the citation relationship diagram is obtained, and θ is equal to the size of the x component and y is equal to the size of the y component. Update φ. If the view is moved (FIG. 8B), the difference between the current coordinate and the previous coordinate of the pointer is obtained, and the current view is moved by the size of the x component and the size of the y component. This feature can provide navigation to the user.

As mentioned above, although the invention made by this inventor was demonstrated concretely according to the said Example, this invention is not limited to the said Example and can be variously changed in the range which does not deviate from the summary. That is, the conversion system 10 inputs a request for changing the viewpoint (ST 2100), changing the z-axis (ST 2110), saving the image file (ST 2120), saving the technical document (ST 2130), and saving the investigation result (ST 2140). The receiving step is not received in the same order as in the above embodiment, and after outputting the citation relationship diagram (ST 2090), the receiving step is performed at any time regardless of the order and performs the next step accordingly.

As described above, according to the method of investigating the citation relationship using the spanning tree according to the present invention, the citation relationship of the patent is shown in three dimensions having a perspective and an angle, so that the citation relationship between the patents is easily obtained.

In addition, according to the method for searching a citation relationship using a spanning tree according to the present invention, the citation relationship diagram and the whole citation relationship diagram at the point of time desired by the user can be obtained without losing the citation relationship information.

In addition, according to the method for searching a citation relationship using a spanning tree according to the present invention, it is possible to grasp the citation relationship between patents more easily to effectively use the patent, pre-application preliminary examination, reference patents and important patents, licensing, etc. The effect is also obtained.

Claims (7)

A citation relationship investigation method comprising a server for examining citation relationship information of a plurality of technical document data and a conversion system for converting citation relationship information input from the server into citation relationship. Requesting, by the conversion system, a citation relationship investigation for a specific technical document to the server; Receiving, by the conversion system, citation relationship information of the technical document sent out by the server; Tracking, by the conversion system, a minimum spanning tree using a common citation factor for each received citation relationship information; The conversion system placing each node of the tracked minimum spanning tree in two dimensions on an x-axis and y-axis plane, Calculating, by the conversion system, coordinates of statistical information to be output on a z-axis at each node of the minimum spanning tree; Outputting a three-dimensional citation relationship diagram having perspective and angle by combining the values of the x, y, and z axes by the conversion system; And a three-dimensional citation relationship diagram outputting the changed three-dimensional citation relationship when the information to be output on the z-axis is changed. The method of claim 1, The step of tracking the minimum spanning tree by using the citation information that is examined by the conversion system, Calculating, by the conversion system, a common citation factor for each of the examined citation relationship information; Generating, by the conversion system, a graph of citation relationships using the calculated common citation coefficients as weights of citation relationships; And the transformation system tracks a minimum spanning tree in the created graph. The method of claim 1, The step of arranging each node of the tracked minimum spanning tree in two dimensions on the x-axis and y-axis planes is performed by applying a spring model using elastic force and repulsion between each node to be placed on the x-axis and y-axis planes. Citation relationship investigation method using a spanning tree, characterized in that. The method of claim 1, The three-dimensional citation relationship diagram is a citation relationship investigation method using a spanning tree, characterized in that the output can be moved horizontally or rotated in accordance with the coordinates and the angle of the viewpoint selected by the user. The method of claim 1, The citation relationship diagram may be a spanning tree, which may be output as a minimum spanning tree, an entire citation relationship for outputting all connection lines, and a total citation relationship for outputting all connection lines in which the minimum spanning tree portion is highlighted. Citation relationship investigation method used. The method of claim 1, Citation relationship investigation method using a spanning tree, characterized in that for storing the technical document of the whole of the citation relationship diagram or a part selected by the user. The method of claim 1, Citation relationship investigation method using a spanning tree, characterized in that for converting the entire or the visible portion of the citation relationship diagram to an image file.

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