Segmentation technique increasing the active vocabulary of speech recognizers

Abstract

A speech recognition system and a method executed by a speech recognition system focusing on the vocabulary of the speech recognition system and its usage during the speech recognition process is provided. A segmented vocabulary and its exploitation is provided comprising a multitude of entries wherein an entry is either identical to a legal word or a constituent of a legal word of the language, and the constituent is an arbitrary sub-component of the legal word according to the orthography. A constituent can comprise any number of characters not limited to a syllable of a legal word or a recognition unit of the speech recognition system. The vocabulary is used to recognize constituents of the vocabulary for recombination of the constituents into legal words if a constituent combination table indicates that the recognized constituents are a legal concatenation in the language.

What is claimed is:  
     
         1 . A speech recognition system for recognition of spoken speech of a language, the speech recognition system comprising: 
 a vocabulary including a multitude of words of said language recognizable by said speech recognition system, the vocabulary comprising a multitude of entries wherein an entry is either identical to a legal word of said language, or an entry is a constituent of a legal word of said language and said constituent is an arbitrary sub-component of said legal word according to the orthography, and further wherein said constituent is not limited to a syllable of said legal word, or said constituent is not limited to a recognition unit of said speech recognition system.    
     
     
         2 . A speech recognition system according to  claim 1 , wherein said vocabulary defines legal words of said language recognizable by said speech recognition system either by an entry itself, or by legal recombination of up to S entries in combination representing a legal word of said language.  
     
     
         3 . A speech recognition system according to  claim 2 , wherein S is 2 or 3.  
     
     
         4 . A speech recognition system according to  claim 3 , wherein said vocabulary comprises, if S is 2, constituents allowing for recombination of legal words from a prefix-constituent and a core-constituent, or from a core-constituent and a suffix-constituent, or from a prefix-constituent and a suffix-constituent and further wherein said vocabulary comprises, if S is 3, constituents allowing for recombination of legal words from a prefix-constituent, a core-constituent and a suffix-constituent.  
     
     
         5 . A speech recognition system according to  claim 2 , further comprising a constituent-combination-table indicating which concatenations of said constituents are legal concatenations in said language.  
     
     
         6 . A speech recognition system according to  claim 5 , further wherein said constituent-combination-table comprises, in the case of S=2 or S=3, at least one of: 
 a core-prefix-matrix indicating whether a combination of a prefix-constituent and a core-constituent is a legal combination in said language or not;    a prefix-suffix-matrix indicating whether a combination of a prefix-constituent and a suffix-constituent is a legal combination in said language or not;    a prefix-prefix-matrix indicating whether a combination of a first-prefix-constituent and a second-prefix-constituent is a legal combination in said language building a third-prefix-constituent or not; and    a core-suffix-matrix indicating whether a combination of a core-constituent and a suffix-constituent is a legal combination in said language or not.    
     
     
         7 . A speech recognition system according to  claim 6 , further wherein for at least one of said core-prefix-matrix, said core-suffix-matrix, said prefix-suffix-matrix, said prefix-prefix-matrix, said core-constituents, said prefix-constituents and said suffix-constituents are represented by unique numbers forming the indexes of said matrixes.  
     
     
         8 . A speech recognition system according to  claim 7 , further comprising a post-processor responsive to an input comprising recognized constituents of said vocabulary for recombination of said constituents into legal words of said language exploiting said constituent-combination-table.  
     
     
         9 . A speech recognition system according to  claim 8 , further wherein said post-processor is at least one of: 
 (a) responsive to two consecutive constituents representing a first prefix-constituent and a second prefix-constituent by one of: 
 recombining said first prefix-constituent and said second prefix-constituent into a third prefix-constituent if said prefix-prefix-matrix is indicating said first prefix-constituent and said second prefix-constituent as a legal combination in said language, and  
 dropping said first prefix-constituent if said prefix-prefix-matrix indicating said first prefix-constituent and said second prefix-constituent as an illegal combination in said language;  
   (b) responsive to two consecutive constituents representing a prefix-constituent and a core-constituent by one of: 
 recombining said prefix-constituent and said core-constituent into a second core-constituent if said core-prefix-matrix is indicating said prefix-constituent and said core-constituent as a legal combination in said language, and  
 if said core-prefix-matrix is indicating said prefix-constituent and said core-constituent as an illegal combination in said language, by replacing said prefix-constituent with an alternative prefix-constituent and recombining said alternative prefix-constituent and said core-constituent if said core-prefix-matrix is indicating said alternative prefix-constituent and said core-constituent as a legal combination in said language;  
   (c) responsive to two consecutive constituents representing a prefix-constituent and a suffix-constituent by: 
 recombining said prefix-constituent and said suffix-constituent into a second prefix-constituent if said prefix-suffix-matrix is indicating said prefix-constituent and said suffix-constituent as a legal combination in said language; and  
   (d)responsive to two consecutive constituents representing a core-constituent and a suffix-constituent by: 
 recombining said core-constituent and said suffix-constituent into a second core-constituent if said core-suffix-matrix is indicating said core-constituent and said suffix-constituent as a legal combination in said language.  
   
     
     
         10 . A speech recognition system according to  claim 9 , further comprising at least one of the steps of: 
 not recombining said prefix-constituent and said suffix-constituent and treating said prefix-constituent as a separate entry if said prefix-suffix-matrix is indicating said prefix-constituent and said suffix-constituent as an illegal combination in said language; and    not recombining said core-constituent and said suffix-constituent and treating said core-constituent as a separate entry if said core-suffix-matrix is indicating said core-constituent and said suffix-constituent as an illegal combination in said language.    
     
     
         11 . A speech recognition system according to  claim 9 , further wherein said alternative prefix-constituent is retrieved from an alternative-list, said alternative-list comprising alternative prefix-constituents to said prefix-constituents in decreasing matching probability.  
     
     
         12 . A speech recognition system according to  claim 1 , further comprising a language-model of said language being computed based on the N-gram frequencies of a sequence of N entries of said vocabulary.  
     
     
         13 . A speech recognition system according to  claim 1 , wherein phones are used as smallest recognition units.  
     
     
         14 . A method for use with a speech recognition system for recognition of spoken speech of a language, said method using a vocabulary including a multitude of words of said language recognizable by said method, said method comprising the step of: 
 identifying, in said spoken speech, entries of said vocabulary wherein an entry is either identical to a legal word of said language, or an entry is a constituent of a legal word of said language and said constituent is an arbitrary sub-component of said legal word according to the orthography, and further wherein said constituent is not limited to a syllable of said legal word or said constituent is not limited to a recognition unit of said speech recognition system.    
     
     
         15 . A method according to  claim 14 , further comprising the step of: 
 post-processing an input comprising recognized constituents of said vocabulary for recombination of said constituents into legal words, said post-processing-step recombining up to S constituents if a constituent-combination-table indicates that said recognized constituents are a legal concatenation in said language.    
     
     
         16 . A method according to  claim 15 , wherein S is 2 or 3.  
     
     
         17 . A method according to  claim 16 , wherein the post-processing step further comprises: 
 recombining, if S is 2, legal words from a prefix-constituent and a core-constituent, or from a core-constituent and a suffix-constituent, or from a prefix-constituent and a suffix-constituent, and recombining, if S is 3, legal words from a prefix-constituent, a core-constituent and a suffix-constituent.    
     
     
         18 . A method according to  claim 17 , wherein the post-processing step further comprises at least one of: 
 (a)recombining two consecutive constituents representing a first-prefix-constituent and a second-prefix-constituent by one of: 
 recombining said first prefix-constituent and said second prefix-constituent into a third prefix-constituent if a prefix-prefix-matrix is indicating said first prefix-constituent and said second prefix-constituent as a legal combination in said language, and dropping said first prefix-constituent if said prefix-prefix-matrix indicating said first prefix-constituent and said second prefix-constituent as an illegal combination in said language;  
   (b)recombining two consecutive constituents representing a prefix-constituent and a core-constituent by one of: 
 recombining said prefix-constituent and said core-constituent into a second core-constituent if said core-prefix-matrix is indicating said prefix-constituent and said core-constituent as a legal combination in said language, and  
 if said core-prefix-matrix is indicating said prefix-constituent and said core-constituent as an illegal combination in said language, replacing said prefix-constituent with an alternative prefix-constituent and recombining said alternative prefix-constituent and said core-constituent if said core-prefix-matrix is indicating said alternative prefix-constituent and said core-constituent as a legal combination in said language;  
   (c)recombining two consecutive constituents representing a prefix-constituent and a suffix-constituent by recombining said prefix-constituent and said suffix-constituent into a second prefix-constituent if said prefix-suffix-matrix is indicating said prefix-constituent and said suffix-constituent as a legal combination in said language; and    (d)recombining two consecutive constituents representing a core-constituent and a suffix-constituent by recombining said core-constituent and said suffix-constituent into a second core-constituent if said core-suffix-matrix is indicating said core-constituent and said suffix-constituent as a legal combination in said language.    
     
     
         19 . A method according to  claim 18 , further comprising at least one of: 
 not recombining said prefix-constituent and said suffix-constituent and treating said prefix-constituent as a separate entry if said prefix-suffix-matrix is indicating said prefix-constituent and said suffix-constituent as an illegal combination in said language; and    not recombining said core-constituent and said suffix-constituent and treating said core-constituent as a separate entry if said core-suffix-matrix is indicating said core-constituent and said suffix-constituent as an illegal combination in said language.    
     
     
         20 . A method according to  claim 18 , wherein said alternative prefix-constituent is retrieved from an alternative-list, said alternative-list comprising alternative prefix-constituents to said prefix-constituents in decreasing matching probability.  
     
     
         21 . A method according to  claim 18 , wherein the post-processing step further comprises: 
 representing said core-constituents, said prefix-constituents and said suffix-constituents by unique numbers used as indexes of said core-prefix-matrix and/or said core-suffix-matrix and/or said prefix-suffix-matrix and/or said prefix-prefix-matrix.    
     
     
         22 . A method according  claim 14 , further comprising the step of using a language-model of said language being based on the N-gram frequencies of a sequence of N entries of said vocabulary.  
     
     
         23 . An article of manufacture for use with a speech recognition system for recognition of spoken speech of a language, said method using a vocabulary including a multitude of words of said language recognizable by said method, the article of manufacture comprising a machine readable medium containing one or more programs which when executed implement the step of: 
 identifying, in said spoken speech, entries of said vocabulary wherein an entry is either identical to a legal word of said language, or an entry is a constituent of a legal word of said language and said constituent is an arbitrary sub-component of said legal word according to the orthography, and further wherein said constituent is not limited to a syllable of said legal word or said constituent is not limited to a recognition unit of said speech recognition system.