Information retrieval system and method of operation

Abstract: The present invention provides, in a database, a technique for automatically indicating what property a current set of documents narrowed by a search criteria possesses, and an approach for retrieving a set of similar documents by specifying a document rather than a keyword. First, in a set of keywords attached to the set of documents narrowed in response to the user retrieval processing, a system according to preferred embodiments of the present invention counts the number of documents to which each of the keywords is attached and displays the keywords in order of decreasing frequency. Next, a user specifies his/her document(s) of interest among the set of documents. In response to this, out of the keywords attached to the documents specified by the user, a keyword able to retrieve any documents other than are specified is displayed. From the set of keywords attached to the current set of document narrowed, this is determined by omitting the keywords meeting the following conditions: (1) the keyword is not attached to any documents other than the specified one; and (2) the keyword is attached to all the documents in the current set of documents. An automatic retrieval with this keyword will enable narrowing by document rather by the keyword.

Description: Field of the invention The present invention relates to a retrieval technique for database(s) holding data, such as newspaper items, patent publication, or image information, in such a manner as to be retrievable by computer processing. Background art Nowadays, databases such as those holding newspaper items, patent publication, or image information in such a manner as to be retrievable by using computers are widely used. In such systems, to make information easier to retrieve, a plurality of keywords are attached for every individual element of the database (for individual articles in a newspaper or for every individual patent publication). To perform a retrieval, generally, an interactive retrieval method called a free keyword scheme is used. According to this, retrieved results are obtained with a user's successive keyword inputs and consequently this method is advantageous for a skilled user in preparing a plurality of retrieval expressions and successively narrowing the extent until a desired number of items are obtained. Such retrieval expressions normally contain logical operations (AND, OR, NOT, and the like) for a plurality of conditions. However, this type of conventional scheme does not makes it possible to predict what degree of effect was given by which condition. In other words, to check that no other literature is omitted than found, the difference in retrieval results between the included case and the removed case for each of the conditions used in retrieval must be verified one by one. However, even a slight increase in the complication of retrieval will so greatly increase the number of combinatorial cases with logical expressions that such methods cannot be applied in practice. Furthermore, because most retrieval systems are designed on the assumption that "users are well acquainted with information to be searched after and its neighbouring fields", an unskilled user unable to think of appropriate keywords finds it difficult to narrow numerous retrieved literatures down to several appropriate literatures. Thus, a system is required that will only require a user to know a general tendency of literatures to be retrieved even if insufficient in knowledge about a field to be retrieved. Further required is a system that presents a group of keywords effective for retrieval to an unskilled user unable to think of appropriate keywords, and navigates even an unskilled user in such a manner as to be able to reach interesting items of information. For this purpose, it becomes necessary to estimate the amount of information or the topicality given by keywords. In this connection, techniques described in the following publications are known. PUPA 63-238622 discloses a keyword-specified information retrieval scheme comprising the steps of installing a means for storing related keywords previously having a relation to a certain keyword, reading related keywords from said keyword storing means by specifying a keyword, and performing information retrieval by using the related keywords. PUPA 2-1057 discloses a method comprising the steps of installing a means for extracting keywords from registered documents and an inverted file creation means for creating an inverted file indicating a relation between the keywords, further creating a keyword connection table for describing related information between the keywords, and selecting a document that meets the retrieval conditions from an inputted keyword by using the inverted file and the keyword connection table. PUPA 3-65763 discloses a retrieval apparatus comprising a keyword extraction means for extracting keywords contained in a retrieval statement, and a retrieval means for retrieving a retrieval target statement under consideration of the strength of relationship between a keyword extracted and the keywords contained in the retrieval target statement. In retrieving data related to the currently displayed data, PUPA 5-35798 discloses a method comprising the steps of retrieving data from a database based on a logical OR of all keywords in the possession of the displayed data, and if a plurality of candidates is found, determining whether an index in the possession of these retrieved data items is contained in elements of the keyword used for retrieval or not, and preferentially displaying data whose index is contained in elements of the keyword used for retrieval. However, the prior art techniques mentioned above have disclosed no technique enabling one to readily determine by what keyword the group of documents obtained from retrieval are inclusively characterized. In addition, a method effective in that one deepens the understanding about one's totally not specialized or unfamiliar field by oneself, is known which comprises the repeated steps of reading a basic introduction to the relevant field or an elementary book, getting and looking through a reference or citation described in the end of the introduction or elementary book, and further referring to literature cited in the reference or citation. If a method similar to this is substantiated by computer processing in a database comprising a plurality of documents, it would assist a user in retrieving a document in his/her unfamiliar field. However, the prior art mentioned above, though giving a technique for narrowing targets of retrieval in accordance with a keyword, suggests no dynamic technique whatever for navigating from one document to another based on the relatedness. Summary of the Invention Viewed from a first aspect, the present invention provides An information retrieval method for retrieving data from a database comprising a plurality of individually identifiable data elements, each data element having keywords attached thereto, the method comprising the steps of: (a) responsive to a retrieval request specifying a search query, retrieving a set of data elements matching the search query; (b) counting the frequency of each attached keyword in the set of data elements; and (c) sorting said keywords based on the count values; and (d) displaying the sorted list of said keywords to the user. Viewed from a second aspect, the present invention provides an information retrieval system for retrieving data from a database comprising a plurality of individually identifiable data elements, each data element having keywords attached thereto, the system comprising: (a) means, responsive to a retrieval request specifying a search query, for retrieving a set of data elements matching the search query; (b) means for counting the frequency of each attached keyword in the set of data elements; and (c) means for sorting said keywords based on the count values; and (d) means for displaying the sorted list of said keywords to the user. The present invention provides a system and method which can automatically indicate the property of the currently narrowed set of documents in a document database. Further, the present invention provides a technique for automatically indicating a keyword effective in further narrowing to a user having no detailed knowledge about the contents of a document database. In a set of keywords attached to the documents narrowed in response to a user's retrieval processing, the present inventive system first performs the process of evaluating the number of documents to which each of the keywords is attached and displaying the keywords according to their frequencies. Based on this information, a user can obtain some idea of what property the narrowed set of documents has. Next, a user may specify a document of interest among a set of documents (to specify a plurality of documents of interest is also possible). In response to this, the system preferably displays keywords capable of retrieving documents other than the document(s) specified by a user among the keywords attached to the specified document(s). This is carried out by determining elements in the set of keywords attached to the specified document(s) from among the set of keywords attached to the set of narrowed documents. However, at this time, the keywords meeting the following conditions are in preferred embodiments omitted: (1) the keyword is not attached to any documents other than the specified one; and (2) the keyword is attached to all the documents in the current set of documents. The system displays the keywords determined by the above approach according to their frequencies. This information enables a user to find what keyword should be specified to obtain a document similar to the specified document. Then, a user can obtain a set of more relevant documents by using such a keyword for further narrowing. Brief Description of the Drawings The present invention will be described further, by way of example only, with reference to a preferred embodiment thereof as illustrated in the accompanying drawings, in which: Figure 1 is a block diagram of a hardware configuration according to a preferred embodiment of the present invention; Figure 2 is a block diagram of a system configuration according to a preferred embodiment of the present invention; Figure 3 is a flowchart of the processing in a first embodiment of the present invention; and Figure 4 is a flowchart of the processing in a second embodiment of the present invention. Description of Preferred Embodiments A. Hardware configuration With reference to Figure 1, a general schema of the system configuration for implementing the preferred embodiments of the present invention is illustrated. This is an ordinary configuration connecting to a bus 101 a central processing unit (CPU) 102 for controlling arithmetic operations and input/output, a main memory (RAM) 104 for storing a program and giving a work space for the CPU 102, a keyboard 106 for key inputting commands or character strings, a hard disk 108 in which are stored an operating system for controlling the CPU 102, a database file, a retrieval engine, index file, and the like, a display device 110 for displaying the retrieved results of a database, and a mouse 112 for pointing to any position on the screen of the display device 110 and conveying the positional information to the CPU. An operating system is used which preferably supports as standard a GUI multi-window environment such as Windows (Microsoft's TM), OS/2 (IBM's TM), X-WINDOW system (MIT's TM) or AIX (IBM's TM), but the present invention is also implementable even in a character base environment such as PC-DOS and MS-DOS (Microsoft's TM) and is not limited to a definite operating system environment. Figure 1 shows a system in a stand-alone environment but, since generally a data file requires a large capacity disk device, it is possible to implement the present invention as a client/server system, to dispose a database file and a retrieval engine at a server machine, to LAN connect a client machine to the server machine through Ethernet, token ring, or the like, and provide only a display control section for viewing the retrieved results on the client machine side. B. System configuration Next, referring to the block diagram of Figure 2, the system configuration of preferred embodiments of the present invention will be described. Incidentally, it should be noted that the elements indicated with individual blocks are stored in the hard disk 108 of Figure 1 individually or collectively as data files. In Figure 2, a document database contains a plurality of documents, newspaper articles and patent publications, and unique IDs are preferably related to individual documents. For keywords extracted from individual documents in the document database 202, the keyword-to-ID index 204 is a file for storing the IDs for one or more documents containing each of them with IDs related to the relevant keyword. For the respective ID for each document in the document database 202, the ID-to-keyword index 206 is a file to store one or more keywords extracted from the document corresponding to the ID while keeping the correspondence relation. Based on a retrieval expression formed of a single keyword or plural keywords combined by logic symbols, the keyword retrieval engine 208 retrieves the keyword-to-ID index 204, accesses the contents of the document database 202 with the ID for the relevant document, and returns the title or the contents of the relevant document. The user input/display module 210 gives a keyword to be retrieved or other commands to the keyword retrieval engine 208 and displays the title or contents of a document returned from the keyword retrieval engine 208. The keyword collection & sort module 212 performs a function to collect data on keywords contained in the documents retrieved by the keyword retrieval engine 208 and the number of documents containing individual keywords, to sort them in order of decreasing number of documents, to provide the data to the user input/display module 210, and to display them onto the display 110. In response of selecting more than one document from the list of documents retrieved by the keyword retrieval engine 208 and displayed on the display 110, the similar document retrieval module 214 omits, among keywords extracted from the selected documents, a keyword that meets either of the following conditions: (1) the keyword is not attached to any document other than the selected one; and (2) the keyword is attached to all the documents in the current set of documents, and retrieves documents by using the highest frequency one in the rest keywords as a retrieval keyword. C. Document retrieval processing C1. 1st embodiment Figure 3 illustrates the flow of processing in a system according to the first embodiment of the present invention. At Step 302 of Figure 3, first, the user input of a keyword is performed using the user input/display module 210 of Figure 2 and keyboard 106. This keyword may be a single keyword or may be a retrieval expression of keywords linked by AND or OR. At Step 304, the keyword or retrieval expression inputted thus is delivered to the keyword retrieval engine 208, by use of which the keyword retrieval engine 208 retrieves the keyword-to-ID index 204 and returns a set of IDs for documents corresponding to the keyword or retrieval expression. At Step 306, based on a set of documents obtained at Step 304, the results of keyword retrieval (number of retrievals, title, or the like) are presented preferably on individual and separate windows in display 110 by the user input/display module 210. At Step 308, all keywords of a specified category, attached to individual documents in the obtained set of documents, are determined and the frequencies for each keyword attached to a set of documents obtained at Step 306 are counted. Incidentally, if no keyword is previously attached to each individual document, the system may be arranged to automatically extract keywords from a set of documents narrowed after retrieval. At Step 310, keywords obtained at Step 308 are sorted preferably in order of decreasing count value by using the module 212 and displayed on individual and separate windows in display 110 by the user input/display module 210 also. By viewing the list of keywords sorted thus in order of descending frequency, a user is made aware of what property is possessed by a set of documents narrowed at Step 306, and can further narrow the set of documents narrowed at Step 306 by using keywords listed. Furthermore, by using the head keyword in the list of keywords sorted in order of decreasing frequency, the system may be arranged to automatically narrow the current set of documents. C2. 2nd embodiment With reference to Figure 4, the flow of a second embodiment of the present invention will now be described. At Step 402 of Figure 4, first, a user's keyword input is performed with the user input/display module 210 and keyboard 106. Herein also, this keyword may be a single keyword or may be a retrieval expression of keywords linked by AND or OR. At Step 404, a keyword or retrieval expression inputted thus is delivered to the keyword retrieval engine 208, and the keyword retrieval engine 208 then retrieves the keyword-to-ID index 204 and returns a set of IDs for documents corresponding to the keyword or retrieval expression. Incidentally, if no keyword is previously attached to each individual document, it may be so arranged as to automatically extract keywords from individual documents in a set of documents narrowed after retrieval. At Step 406, based on a set of IDs for documents obtained at the Step 404, the results of keyword retrieval (number of retrievals, titles, and the like) are displayed preferably on a separate window in the display 110. At Step 408, by viewing titles of the list resultant from a retrieval displayed on a separate window as a result of Step 406, a user selects one or plural documents that seem to be of interest. This is executable, for example, by clicking the displayed row of the relevant title with the mouse 112. The clicked row of title display is displayed in an inverse video and is understood to be selected. At Step 410, all keywords of a specified category, attached to individual documents in the obtained set of documents, are determined and the frequencies for each keyword attached to a set of documents are obtained and the frequencies for each keyword attached to a set of documents obtained at Step 404 are counted. At Step 412, from a set of documents obtained at Step 404 by using the similar document retrieval module 214, the system selects a keyword having the highest frequency among those keywords attached to a specified document which do NOT meet any of the following conditions: (1) the keyword is not specified in any documents other than the specified one; and (2) the keyword is attached to all the documents in the current set of documents. At Step 414, the system retrieves the current set of documents with the obtained keyword taken as a retrieval keyword. Incidentally, at Step 414, instead of retrieving the current set of documents with the obtained keyword taken as a retrieval keyword, the system may list the keywords meeting the conditions (1) and (2) mentioned above along with their frequencies, preferably in order of decreasing frequency, thereby allowing a user to select his/her desired keyword. D. Example of a navigation processing An example of performing a retrieval and navigation by using the system according to the embodiments mentioned above in a database in which newspaper articles for a definite period are collected will now be described. First, as a result of retrieval concerning the keyword "accident", the number of hits was 109. In response to this retrieval processing, a window entitled "Article subcategory display" is opened in accordance with the processing shown in the flowchart of Figure 3, displaying the list of keywords contained in the retrieved documents that are arranged in order of decreasing frequency. New tram 32 Cause 29 Runaway 27 Runaway accident 27 System 23 Death 22 Traffic system 21 Resume 20 Accident causation 17 Safety 16 Running resumption 16 Also, at the same time, dates and titles of the 109 articles retrieved are displayed in another window as follows: 931101 Since the accident of Chernobyl atomic power station, the real status of old soviet made atomic reactors has been gradually 931101 Possible cause of runaway accident, faulty in new tram relay 921101 New tram runaway accident, faulty in a relay device, relay in the 3rd car 931101 TOMEI Speedway, trucks and buses totally burnt -- fire arising from loaded paints or the like 931102 Burn due to pans ceaseless -- caution against grips On selection of an article, entitled "Since the accident of Chernobyl atomic power station ....", on this window indicating dates and titles, for example, by the user clicking a title with the mouse, the relevant row is displayed in inverse video. At this time, selection of plural articles is also possible by a similar operation. Upon the user making a similar document selection by clicking the button entitled "Similar document" on the screen, for the articles selected by the processing shown in the flowchart of Figure 4, the highest frequency keyword of those NOT meeting any of the following conditions: (1) the keyword is not specified in any articles other than the specified one; and (2) the keyword is attached to all the articles in the current set of articles retrieved; is selected by the system. In this example, such a keyword is "Safety", and the system automatically performed a retrieval concerning the keyword of "Safety" in the current set of retrieved articles and obtained 16 hits of articles therefrom. By viewing the titles or contents of these 16 articles, a user came to be navigated to articles related to the title "Since the accident of Chernobyl atomic power station ....." and thereby could deepen the understanding of his/her interesting articles. As described above, the preferred embodiments of the present invention enable a user to take a look at the property of the set of documents narrowed from the list of keywords automatically created by the system and view related documents in sequence without a definite previous knowledge, this being achieved by the system automatically navigating the user to other documents related to the document selected by the user. In such a way, the preferred embodiments of the present invention allow for search by document rather than by keyword.

Claims: An information retrieval method for retrieving data from a database comprising a plurality of individually identifiable data elements, each data element having keywords attached thereto, the method comprising the steps of: (a) responsive to a retrieval request specifying a search query, retrieving a set of data elements matching the search query; (b) counting the frequency of each attached keyword in the set of data elements; and (c) sorting said keywords based on the count values; and (d) displaying the sorted list of said keywords to the user. A method as claimed in claim 1, further comprising the step of: (e) searching for further data elements by using the keyword having the highest count value among said keywords. A method as claimed in claim 1 or claim 2, further comprising the initial step of extracting keywords from the individual data elements in said set. A method as claimed in any of claims 1 to 3, further comprising the steps of: displaying the contents of the given set of said data elements or part of the contents or titles thereof; in response to the user selection of at least one data element out of said given data elements, selecting a keyword having the highest count value among those which do NOT meet any of the following conditions: (i) the keyword is not attached to any documents other than the selected one; and (ii) the keyword is attached to all the documents in the given set of documents; and searching for further data elements by using the selected keyword. An information retrieval system for retrieving data from a database comprising a plurality of individually identifiable data elements, each data element having keywords attached thereto, the system comprising: (a) means, responsive to a retrieval request specifying a search query, for retrieving a set of data elements matching the search query; (b) means for counting the frequency of each attached keyword in the set of data elements; and (c) means for sorting said keywords based on the count values; and (d) means for displaying the sorted list of said keywords to the user. An information retrieval system as claimed in claim 5, further comprising: means (210) for displaying the contents of the given set of said data elements or part of the contents of titles thereof; means (214), responsive to the user selection of at least one data element out of said given data elements, for selecting a keyword having the highest count value among those which do NOT meet any of the following conditions: (i) the keyword is not attached to any documents other than the selected one; and (ii) the keyword is attached to all the documents in the given set of documents; and means for searching for further data elements by using the selected keyword. An information retrieval system as claimed in claim 5 or claim 6, wherein the sorting means (212) is arranged to sort said keywords in decreasing order of the count values.

Inventors: NOMIYAMA HIROSHI, NOMIYAMA, HIROSHI
Applicants: IBM, INTERNATIONAL BUSINESS MACHINES CORPORATION
Application year: 1996
Main classification: G06F17
IPC codes: G06F17