Abstract:
A system that intelligently abstracts and archives a document for storage and interprets a free form user retrieval query to recall the document from the storage file. The system includes a method for automatically selecting keywords from the document using a parts of a speech directory. A method is given for weighing the importance or centrality of each keyword with respect to the document of its origin. Using the same logic paths, a free form query that describes the document in the same manner that it would have to be described to a secretary to &#34;find&#34; it in a filing cabinet, the system automatically determines the key matching terms and finds the archived document(s) with the greatest affinity.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to information storage and retrieval and more particularly to methods of automatically abstracting, storing and retrieving documents using free form inquiry. 
     2. Description of the Prior Art 
     In implementing a document storage and retrieval system, the practicality and utility of such a facility is governed by the ease that respective documents are catologed into the system and the efficiency with which a user&#39;s request can be associated with the related document catalog representation (description). State of the art document storage and retrieval is based on manually selecting keywords to represent a document in the system&#39;s catalog or index and then effecting retrieval by recalling from memory appropriate keyword terms and either automatically or manually searching the index for an &#34;appropriate&#34; level of match against the prestored keywords. Procedures have been developed in the prior art for abstracting documents and retrieving them based on keyword matching. One of the procedures requires the requestor to supply in a fixed format certain details about the subject document such as: author, addressee, date and keywords or phrases. For retrieval, a summary sorted listing is prepared under each of the above headings. The requestor must discern the appropriate document by examining the entries under the retrieval information headings. No latitude is allowed in the search clues. The search may be done by manual perusal or using data processing global find commands. 
     A second procedure stores all non-trivial words (i.e., ignores articles and pronouns, etc.) in a document as a totally inverted file. The document/line/word position of origin is maintained in the catalog. Search of the database for retrieval is effected by the user supplying keywords based on the user&#39;s memory. The catalog is automatically searched with the added facility that the user can specify relations that must exist between the keywords as they exist in the original text (i.e., keyword 1 is before keyword 2, etc.). An example of such a system is the IBM Data Processing Division product Storage and Information Retrieval System, commonly called STAIRS. 
     A third method for document storage and retrieval is simply storing the document in machine readable form and searching all documents using a &#34;global find&#34; logic for each user supplied keyword. In theory and in practice for small data bases, the &#34;global find&#34; can be replaced by the user reviewing the documents verbatim as they are displayed on a CRT type device. 
     However, in all the above procedures for document storage and retrieval, the major intelligent burden for abstraction and retrieval association matching is put on the user. Where the system aids in abstraction or matching, it is done at the cost of voluminous cataloging procedures, massive data processing burden and a structure format is required for the user to communicate for retrieval with the system. 
     SUMMARY OF THE INVENTION 
     It has been discovered that all non-trivial correspondence is made topic specific by a relatively small number of message specialization terms. These are the words that transfrom the &#34;boiler plate&#34; of business correspondence into the message that the author wishes to convey. These terms consist mainly of numerics, proper names, acronyms, nouns and single purpose adjectives. Any meaningful description of a document for query purposes must contain at least some of these terms which give the document its particular meaning. This invention includes a technique for reliably locating the message specialization terms in a document and forming an abstract of the document using these terms. The technique utilizes the data storage technology disclosed in U.S. Pat. No. 3,995,254 issued Nov. 30, 1976 to W. S. Rosenbaum and incorporated herein by reference to store a dictionary of words for spelling verification, however, other dictionary storage methodologies could also be used. The specialization terms in the dictionary memory additionally have a data bit appended to them to indicate their status as a noun or single purpose adjective. Numerics, proper names, and acronyms are not stored in the dictionary memory. The test of the document is compared with the contents of the dictionary memory and those words that compare to nouns and single purpose adjectives in the dictionary and those words (proper names, numerics, acronyms) not found in the dictionary memory are accumulated to form an abstract of the document. Each word in the abstract is then stored in a word index file. Records in the word index file include the word, the identification code of the document(s) in which the word occurs, the number of times the word occurs in each respective document, an indicator as to whether the word is a numeric, proper name/acronym, noun/single purpose adjective, and an indicator as to whether the word occurs in the header, trailer, body or copy list of the document. (A single purpose adjective is a word whose primary use is adjectival, for example heavy, round, old, new, the colors red, blue, etc.) The words in an input query for retrieval of a document are compared against the word index file. Since some words in the word index file may occur in several documents, weighing factors are accorded each word based on the information stored with the word in the word index file. A score is accumulated for each document that contains any of the words in the retrieval query and those documents with highest scores are presented to the user for review. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of system components in the document storage and retrieval system. 
     FIG. 2 is a flow chart of the operation in abstracting and storing a document. 
     FIG. 3 is a flow chart of the operation of the system in retrieving a document in response to a user query. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1 there is shown a block-diagram of a document storage and retrieval system which includes a processor or CPU 10 of the general purpose type which is capable of decoding and executing instructions. The processor 10 is in two-way communication over bus 13 with a memory 14 containing instructions which control its operation and define the present invention. The processor 10 is also in a two-way communication over bus 7 with memory 8 which contains a partial speech dictionary where all nouns and single purpose adjectives are so noted. The memory 8 contains no numerics, acronyms or proper names. The processor 10 is also in two-way communication over bus 11 with main memory 12 which is used for storing the documents and key word index files. The instruction memory 14 and dictionary memory 8 may be of the read only storage or random access storage type, while the main memory 12 is of the random access storage type. 
     For document abstracting and archiving an input register 16 receives the text words from a source (not shown) over bus 17. The source may be any of various input devices including keyboard, magnetic tape reader, magnetic cards/disk/diskette files, etc. Text words are presented to processor 10 by register 16 over bus 15 for processing in accordance with instructions stored in instruction memory 14. The results of the processing (abstraction) performed on the text contents of register 16 are transmitted to memory 12 over bus 11. 
     For document retrieval, input register 16 receives the query text statement from a source (not shown) over bus 17. The source may be any of various input devices such as a keyboard, script table, or especially constituted touchtone pad. The query statement text is presented to processor 10 by register 16 over bus 15 for processing in accordance with instructions stored in instruction memory 14. The processor 10 under control of instructions from instruction memory 14 communicates with the contents of dictionary memory 8 over bus 7 and memory 12 over bus 11 to perform a document retrieval affinity evaluation on the contents of memory 12. The selected document(s) are transmitted from memory 12 over bus 11 and bus 9 to output register 18 and from output register 18 over bus 19 to a utilization device which may take various forms, including a display, printer or voicecoder, etc. The selected document(s) are then presented to the user for review. 
     The preferred embodiment of the present invention comprises a set of instructions or programs for controlling the document abstracting, archiving and query statement affinity match for retrieval for the document storage and retrieval system shown in FIG. 1. Referring to FIG. 2 there is shown a flow chart of the programs for abstracting and archiving documents. 
     It is standard practice in data processing systems having on-line storage to assign each record stored a unique identifier code or number. This code is usually eight characters in length and does not contain information that is descriptive of the contents of the record because of the limited length. The identifier code is useful for accessing the records where the user is able to associate the identifier code with a particular record. However, this technique for locating a record become impractical where the data base is large and several users have access to the same records. A record usually retains the same identifier code throughout its existence and modifications to the record replace the record in storage under the same identifier code. The program for abstracting and archiving documents makes use of the identifier code by including it as part of the abstract record. When a document is entered into the System, FIG. 2, the document identifier code or number for the document is read at block 20 and the word index files already stored in the system are compared to determine if a match is found indicating that an abstract is currently stored for the document. 
     
                                           TABLE 1__________________________________________________________________________Document Abstraction Routine__________________________________________________________________________BEGINPROCEDURE(OCRS --ABSTRACT);ENTER ABSTRACT, SAVE DOCUMENT NUMBER PARAMETER;READ DOCUMENT ABSTRACT FILE RECORD FOR DOCUMENT NUMBER;IFRECORD FOUNDTHENCALL (DELETE --ABSTRACT);ENDIF;WHILENOT END OF DOCUMENTDOWHILENOT END OF PAGEDOGET NEXT LINE OF TEXT FROM THE DOCUMENT;WHILEMORE CHARACTERS EXIST ON THE LINEDOGET NEXT WORD FROM THE LINE (2 OR MORECONSECUTIVE CHARACTERS A-Z, 0-9, OR&#39;);IFTHE WORD IS &#34;CC&#34;THENSET CC LINE NUMBER TO THE DOCUMENTLINE NUMBER MINUS 1;ENDIF;CALL (ABSTRACT --PROCESS --WORD);ENDWHILE;INCREMENT PAGE NUMBER BY 1;ENDWHILE;INCREMENT DOCUMENT LINE NUMBER BY 1;ENDWHILE;SET LAST BODY LINE COUNT TO THE LESSOR OF:THE CC LINE NUMBER AND THE DOCUMENT LINE NUMBER;DECREMENT THE LAST BODY LINE COUNT BY 4;CALL (ABSTRACT --END --PROCESSING);ENDPROCEDURE(OCRS --ABSTRACT):__________________________________________________________________________ 
    
     Table 1 is the program routine in Program Design Language (PDL) for abstracting the document. If the document number (identifier code) is found to exist in the abstract file, the program routine branches to the delete abstract routine of Table 2 which is shown as block 22 of the flow chart of FIG. 2. 
     
                                           TABLE 2__________________________________________________________________________Delete Abstract Subroutine__________________________________________________________________________BEGINPROCEDURE(DELETE --ABSTRACT);ENTER DELETE ABSTRACT;WHILENOT END OF DOCUMENT ABSTRACT RECORDDOGET THE NEXT ENTRY IN THE DOCUMENT ABSTRACT RECORD;READ THE WORD INDEX RECORD FOR THE WORD;WHILENOTE END OF WORD INDEX RECORDDOGET THE NEXT ENTRY IN THE WORD INDEX RECORD;IFTHE DOCUMENT NUMBER IN THE ENTRY IS THESAME AS THE DOCUMENT NUMBER FROMTHE DOCUMENT ABSTRACT RECORDTHENREMOVE THE ENTRY FROM THE WORD INDEXRECORD;IFTHERE ARE NOW NO ENTRIES IN THE WORDINDEX RECORDTHENDELETE THE WORD INDEX RECORD FROMTHE FILE;ELSEREWRITE THE WORD INDEX RECORD TO THEFILE;ENDIF;ENDIF:ENDWHILE;ENDWHILE;DELETE THE DOCUMENT ABSTRACT RECORD FROM THE FILE;ENDPROCEDURE(DELETE --ABSTRACT);__________________________________________________________________________ 
    
     The delete abstract subroutine of Table 2 deletes the abstract from memory by deleting occurrences of the words in the abstract from the word index file. The makeup of the word index file will be fully explained below. 
     Following deletion of the existing abstract from memory, or, if no words having the document number are stored in the word index file, the document is processed at block 23 to create an abstract. Referring to the program routine in Table 1, the next word in the document is tested to determine if the Carbon Copy (CC) list follows. If not, the program branches to abstract process word routine in Table 3 to determine if the word should be included in the abstract for the document. 
     
                       TABLE 3______________________________________Abstract Process Word Subroutine______________________________________ BEGINPROCEDURE(ABSTRACT --PROCESS  --WORD);ENTER PROCESS WORDINCREMENT DOCUMENT WORD COUNT BY 1;LOOK THE WORD UP IN THE DICTIONARY;IFTHE WORD WAS FOUND IN THE DICTIONARY BUTNOT FLAGGED AS A NOUN OR A SINGLEPURPOSE ADJECTIVETHENIGNORE THIS WORD;ELSEIFTHE WORD WAS FOUND IN THE DICTIONARY BUTFLAGGED AS A NOUN OR A SINGLE PURPOSEADJECTIVETHENFLAG THE WORD AS NORMAL;ELSEFLAG THE WORD AS ACRONYM;ENDIF;IFTHIS WORD HAS NOT BEEN FOUND PREVIOUSLY INTHIS DOCUMENTTHENSAVE THIS WORD;SAVE THE DOCUMENT LINE COUNT;SET FREQUENCY COUNT FOR THIS WORD TO 1;ELSEINCREMENT FREQUENCY COUNT FOR THIS WORD BY 1;ENDIF;ENDIF;ENDPROCEDURE(ABSTRACT --PROCESS  --WORD);______________________________________ 
    
     As was previously stated, the criteria for determining whether a word is included in the abstract is whether the word is determined to be a &#34;message specialization term&#34;, i.e., a noun, single purpose adjective, proper name, acronym, or numeric. The program routine of Table 3 compares the word to the contents of dictionary memory 108 (FIG. 1). If the word is found in the dictionary memory but it is not a noun or single purpose adjective then the word is ignored. The decision as to whether a word in the dictionary is a noun or single purpose adjective is made at the time of preparation of the dictionary memory 8 and those words designated as nouns or single purpose adjectives have appended to them a code bit. If the word is determined to be a noun or single purpose adjective, a code bit or &#34;flag&#34; is added to the word to indicate as &#34;normal&#34;. If the word is not in the dictionary then a code bit or &#34;flag&#34; is added to the word to indicate its status as acronym or proper name. Acronyms and proper names are considered to have more influence as message specialization terms than nouns and single purpose adjectives and therefore are more useful for document retrieval as will be shown below. The Process Word routine of Table 3 controls the processor 10 to save only one copy of each abstract term for storage in the word index file. However, the Process Word routine appends to the word the number of each line in the document where the word appears and a count of the number of times the word appears in the document. As will be seen below for document retrieval, the frequency of occurrence of the word in the document and the place of occurrence help determine the value of the word as a query term for retrieving the document. 
     Following completion of the Word Process subroutine control returns to the Abstract routine in Table 1 which repeats the routines for each word in the document. The Abstract routine accumulates a count for the number of pages in the document. Upon reaching the end of the document a count is calculated to determine the fifth line from the end of the body of the document and the Abstract End Processing subroutine of Table 4 is selected. 
     
                                           TABLE 4__________________________________________________________________________Abstract End Processing Subroutine__________________________________________________________________________BEGINPROCEDURE(ABSTRACT --END --PROCESSING);ENTER END PROCESSING;CREATE A DOCUMENT ABSTRACT RECORD CONSISTING OF;THE DOCUMENT NUMBER, THE DOCUMENT WORD COUNT, ANDEACH WORD IN THE ABSTRACT;WRITE THE DOCUMENT ABSTRACT RECORD TO THE FILE;WHILEMORE WORDS ARE LEFT TO PROCESS;DOREAD THE WORD INDEX RECORD FOR THE WORD;IFTHE RECORD WAS NOT FOUNDTHENCREATE A WORD INDEX RECORD CONSISTING OF:THE WORD, THE NORMAL/ACRONYM/PROPER NAMEFLAG, THE DOCUMENT NUMBER, THE FREQUENCYCOUNT, AND A FLAG INDICATING IN HEADER/TRAILER/CC LIST/BODY;WRITE THE WORD INDEX RECORD TO THE FILE;ELSEADD THE DOCUMENT NUMBER, THE FREQUENCY COUNT,AND A FLAG INDICATING IN HEADER/TRAILER/CCLIST/BODY TO THE RECORD;REWRITE THE WORD INDEX RECORD TO THE FILE;ENDIF;ENDWHILE;ENDPROCEDURE(ABSTRACT --END --PROCESSING);__________________________________________________________________________ 
    
     The Abstract End Processing subroutine controls the processor 10 to create an abstract record which includes all words saved by the Process Word subroutine of Table 3, a count of the number of words in the document and the document identifier code number. The Abstract End Processing subroutine also creates a Word Index Record for each word in the abstract record which includes the word, the &#34;normal&#34; or &#34;acronym/proper name&#34; code, the document number, the number of pages in the document, the frequency of occurrence of the word in the document, and a code indicating whether the word occurs in the header (first 10 lines), trailer (last 5 lines) or the copy list or body of the document. The words in the Word Index File are searched to determine if a record for the word already appears in the Word Index File. If it does then the record is updated by adding the document number, frequency count, and codes such that no duplicates of the word appear in the Word Index File. Following completion of the Abstract End Processing subroutine of Table 4 control returns to the Abstract routine of Table 1 which terminates the abstracting procedure. 
     To retrieve a document stored in the system, the requestor must enter a query for the document into the system. This may be done through a keyboard, for example. The queries used with the preferred embodiment of this system can be a natural language statement or string of words that describes the item. The search argument is created by testing the query words against the word index file. In many cases, the words in the search argument will occur in the key word records (abstracts) of several documents. In order to provide better discrimination between contending documents, different weights are applied to different key words. Weighting criteria are applied according to these general rules: 
     1--Matches on numeric key words are given greater weight than matches on alpha key words. 
     2--Matches with key words that are proper names or acronyms are given greater weight than matches with nouns or single purpose adjectives that are found in the dictionary memory. 
     3--The weight assigned to a key word match is proportional to the number of times that the word occurred in the document divided by the log of the number of pages in the document. 
     4--Matches with key words that occur in the first ten lines of the document are given greater weight than those of key words in the center of the body of text. 
     5--Matches that occur with key words in the last five lines of text (before any copy lists) are given more weight than matches with words in the center of the text, but less weight than matches with words in the first ten lines. 
     6--The weight of a key word match is increased when that word is the name of a month or year. 
     7--The weight of a key word match is inversely proportional to the number of documents in the entire file that contain that key word in the body of the document (excluding occurrences as part of the copy list). 
     The rationale behind these general rules is to give the greatest weight to those matches that involve key words that have the most narrowly specific meaning. It is assumed that specific names, numbers and dates have very specific meaning so they are weighed heavily. It is also assumed that the most specific items will be mentioned at the beginning or end of the correspondence. Hence, words occurring in these regions are also given greater weight. An example of an expression that satisfies the general rules is the following: ##EQU1## where: 
     F i ,j =number of times ith key word appears in jth document divided log 2  of the number of pages in document. 
     A i  =binary indicator if ith key word is an acronym or proper name. 
     K i  =binary indicator if ith key word occurs in first 10 lines. 
     L i  =binary indicator if ith key word is a numeric. 
     E i  =binary indicator if ith key word occurs in last 5 lines. 
     H i  =binary indicator if ith key word occurs in the dictionary as a noun or single purpose adjective. 
     M i  =binary indicator if ith key word is a month. 
     Y i  =binary indicator if ith key word is a year. 
     D i  =number of documents that contain ith key word. 
     Referring to FIG. 3, a flow chart of the processing of a query for a document is shown. At block 30 the user query is input to the processor 10 (FIG. 1) from input register 16 over bus 15. Tables 5, 6, and 7 show program routines for processing the user query according to the general rules stated above. 
     
                       TABLE 5______________________________________Query Routine______________________________________BEGINPROCEDURE(OCRS --QUERY);ENTER QUERY;WHILEMORE QUERY LINES OF TEXT EXISTDOGET THE NEXT LINE OF QUERY TEXT;WHILEMORE CHARACTERS EXIST ON THE LINEDOGET THE NEXT WORD FROM THE LINE (2 OR MORECHARACTERS A-Z, 0-9, OR &#39;);READ THE WORD INDEX RECORD FOR THE QUERYWORDIFWORD FOUNDTHENCALL (QUERY --PROCESS --WORD);ENDIFENDWHILE;ENDWHILE;CALL (QUERY --END --PROCESSING);ENDPROCEDURE(OCRS --QUERY);______________________________________ 
    
     The Query routine of Table 5 compares the query words to the contents of the word index file as shown in block 31 of the flow diagram of FIG. 3. The query words that match the word index file are processed at block 32 of the flow diagram by the Query Word Process subroutine of Table 6. 
     
                       TABLE 6______________________________________Query Process Word Subroutine Detailed Logic______________________________________BEGINPROCEDURE(QUERY --PROCESS --WORD);ENTER PROCESS WORD;IFTHE WORD IS A YEARTHENSET INDICATOR FOR YEAR IN QUERY;ENDIF;IFTHE WORD IS A MONTHTHENSET INDICATOR FOR MONTH IN QUERY;ENDIF;IFTHE WORD IS NUMERICTHENSET NUMBER WEIGHT TO 10;ELSESET NUMBER WEIGHT TO 0;ENDIF;THENCOUNT THE NUMBER OF DOCUMENTS CONTAININGTHIS WORD;COUNT THE NUMBER OF DOCUMENTS WHERETHE WORD IS NOT IN THE CC LIST;IFTHE WORD INDEX RECORD IS FLAGGED AS AN ACRONYM/PROPER NAMETHENSET ACRONYM/PROPER NAME WEIGHT TO 10;ELSESET NORMAL WEIGHT TO 5;ENDIF;WHILEMORE DOCUMENT ENTRIES ARE IN THE WORD INDEXRECORDDOGET THE NEXT DOCUMENT ENTRY FROM THE WORDINDEX RECORDIFTHE FLAG INDICATES THAT THE WORD OCCURREDIN THE HEADERTHENSET HEADER WEIGHT TO 10;ELSESET HEADER WEIGHT TO 0;ENDIF;IFTHE FLAG INDICATES THAT THE WORD OCCURREDIN THE TRAILERTHENSET TRAILER WEIGHT TO 5;ELSESET TRAILER WEIGHT TO 0;ENDIF;IFTHE FLAG INDICATES THAT THE WORD OCCURREDIN THE CC LISTTHENSET CC DIVIDE WEIGHT TO 99,999;ELSESET CC DIVIDE WEIGHT TO 1;ENDIF;SET THE RETRIEVAL VALUE TO:(ACRONYM/PROPER NAME WEIGHT + NUMBERWEIGHT + NORMAL WEIGHT + HEADER WEIGHT +TRAILER WEIGHT + WORD FREQUENCY DIVIDEDBY THE LOG BASE 2 OF COUNT OF NUMBER OFPAGES) DIVIDED BY THE LOG BASE 2 OF THECOUNT OF DOCUMENTS NOT CONTAINING THEWORD IN THE CC LIST;DIVIDE THE RETRIEVAL VALUE BY THE CC DIVIDEWEIGHT;IFTHIS DOCUMENT HAS NOT BEEN ANALYZED YETIN THIS QUERYTHENSAVE THE DOCUMENT NUMBER;SAVE THE RETRIEVAL VALUE;ELSEINCREMENT THE DOCUMENTS RETRIEVAL VALUEBY THE NEW RETRIEVAL VALUE;ENDIF;ENDWHILE;ENDPROCEDURE(QUERY --PROCESS --WORD);______________________________________ 
    
     Each query word is tested to determine if it is a month, year, numeric, acronym or normal (noun or single purpose adjective). The subroutine of Table 6 also adds weighting factors if the indicators in the word index file show the word occurs in the first ten lines (Header) of the document, last five lines (Trailer) of the document, or occurs more than once in the document. The value of the word is reduced if it occurs in the copy list of the document or occurs in more than one document. An overall calculation of value for each word is calculated and a total value for all query words that match words in the word index file for each document number having any matches is accumulated. The steps of calculating the retrieval value for words and the retrieval value for documents are shown in block 33 and 34 of FIG. 3. Following processing of all words in the query, the Query routine of Table 5 branches to the Month/Year Evaluation subroutine of Table 7. 
     
                       TABLE 7______________________________________Query Month/Year Evaluation______________________________________BEGINPROCEDURE(QUERY --END --PROCESSING);ENTER END PROCESSING;IFTHERE WAS A YEAR MENTIONED IN THE QUERYTHENINCREMENT THE RETRIEVAL VALUE OF EACHDOCUMENT THAT DID CONTAIN THE YEAR BY 20%;ENDIF;IFTHERE WAS A MONTH MENTIONED IN THE QUERYTHENINCREMENT THE RETRIEVAL VALUE OF EACH -DOCUMENT THAT DID CONTAIN THEMONTH BY 20%;ENDIF;RETRIEVE THE DOCUMENT NUMBERS OF THEDOCUMENTS WHOSE RETRIEVAL VALUE IS WITHIN25% OF THE HIGHEST RETRIEVAL VALUE;SORT THIS LIST BY THE NUMBER OF WORDS FROMTHE QUERY ACTUALLY OCCURRINGIN THE DOCUMENT;OUTPUT THE DOCUMENTS;ENDPROCEDURE(QUERY --END --PROCESSING);______________________________________ 
    
     The subroutine of Table 7 increases the retrieval value for each document that contains a year and/or month that matches a year and/or month in the query. The subroutine of Table 7 then controls the processor 10 to output those documents from main memory 12 to output register 18 whose retrieval value is within 25 percent of the highest retrieval value calculated. Control is then returned to the Query routine of Table 5 which terminates the query procedure. 
     While the invention has been shown and described with reference to a specific set of computer instructions, i.e. PDL, and retrieval weighting values, it will be understood by those skilled in the art that the spirit of this invention can be implemented in other computer languages and the set of document retrieval weighting factors can be modified without avoiding the scope of the invention claimed herein.