Patent Publication Number: US-5839107-A

Title: Method and apparatus for automatically generating a speech recognition vocabulary from a white pages listing

Description:
FIELD OF THE INVENTION 
     This invention relates to a method and an apparatus for automatically performing desired actions in response to spoken requests. It is particularly applicable to a method and an apparatus for automatically providing desired information in response to spoken requests, as may be used to partially or fully automate telephone directory assistance functions. 
     BACKGROUND OF THE INVENTION 
     In addition to providing printed telephone directories, telephone companies provide telephone directory assistance services. Users of these services call predetermined telephone numbers and are connected to directory assistance operators. The operators access directory databases to locate the directory listings requested by the users, and release the telephone numbers of those listings to the users. 
     Because telephone companies handle a very large number of directory assistance calls per year, the associated labor costs are very significant. Consequently, telephone companies and telephone equipment manufacturers have devoted considerable effort to the development of systems which reduce the labor costs associated with providing directory assistance services. 
     In a typical directory assistance system the caller is first prompted to provide listing information, in other words to specify in what area resides the business or individual whose telephone number he seeks. If valid speech is detected, the speech recognition layer is invoked in an attempt to recognize the unknown utterance. On a first pass search, a fast match algorithm is used to select the top N orthography groups from a speech recognition dictionary. In a second pass the individual orthographies from the selected groups are re-scored using more precise likelihoods. The top orthography in each of the top two groups is then processed by a rejection algorithm which evaluates if they are sufficiently distinctive from one another so the top choice candidate can be considered to be a valid recognition. 
     Usually the speech recognition dictionary that contains the orthographies potentially recognizable by the speech recognition layer on a basis of a spoken utterance by a user is created from screened tokens. These are actual call records in which are stored the spoken request by the user. This information allows to determine how people verbally formulate requests in connection with a certain entity whose telephone number is being sought. For example, the business &#34;The First Wall of Glass Company&#34; on Wilmington street, may be requested in a variety of different ways, such as &#34;Wall of Glass&#34;, &#34;First Wall of Glass on Wilmington&#34;, First Wall of Glass Company&#34; and &#34;Wall of Glass on Wilmington&#34;, among others. After examining the different formulations associated with the entity, orthographies are created, where each orthography corresponds to an particular request formulation. Thus, for each entry in the white pages a number of orthographies are produced that collectively form a speech recognition vocabulary. In practice, not all possible formulations are retained to avoid creating extremely large speech recognition vocabulary that may not be able to offer real-time performance. Only the formulations that occur the most often are retained. 
     Although the use of screened tokens allows to construct a precise speech recognition vocabulary that well reflects the manner in which spoken requests are formulated, this method is time consuming and very expensive to put in practice. Indeed, a large number of screened tokens are required to construct a useful vocabulary, in the order of 50,000 to 100,000. 
     Thus, there exists a need in the industry to develop automated methods for generating a speech recognition vocabulary that at least partially reduces the reliance on screened tokens to complete this task. 
     OBJECTS AND STATEMENT OF THE INVENTION 
     An object of the present invention is to provide a method for generating a speech recognition vocabulary from a listing containing a plurality of entries. 
     Another object of the present invention is to provide an apparatus for generating a speech recognition vocabulary from a listing containing a plurality of entries. 
     A further object of the invention is a computer readable medium containing a program element that instructs a computer to process a listing to generate a speech recognition vocabulary. 
     The present inventors have made the unexpected discovery that a useful speech recognition vocabulary may be automatically created by applying to a listing a heuristics model that simulates the manner in which spoken requests can be made. Typically, the listing contains entries, names of individuals for example, that the speech recognition system can potentially identify based on a spoken utterance by the user. In a specific example, the listing may be a white pages list that is a source of information associating an entity name, such as an individual or a business with a telephone number or some pointer leading to a telephone number. Most preferably, the white pages also provide civic address information for each entity. In essence, the heuristics model observes the different words from which the entry in the entry in the listing is constructed and combines those words in a different manner to create orthographies that mimic the way a query of that particular entry is likely to be made. 
     As embodied and broadly described herein the invention provides a method for generating a speech recognition vocabulary for use in a speech recognition system, the method comprising the steps of: 
     providing a computer readable medium containing a listing of a plurality of entity identifiers, each entity identifier including at least one word that symbolizes a particular meaning, said plurality of entity identifiers being distinguishable from one another based on either one of individual words and combinations of individual words, at least some of said entity identifiers including at least two separate words; 
     generating for each one of said at least some of said entity identifiers an orthography set including a plurality of orthographies, each orthography in a given set being a composition of different words and at least one of said different words being selected from a respective entity identifier; 
     storing said orthography set on a computer readable medium in a format such that the orthographies of said set are potentially recognizable by a speech recognition system on a basis of a spoken utterance by a user. 
     In a preferred embodiment, the above defined method is used to generate a speech recognition vocabulary for use in an automated directory assistance system. The list of entity identifiers is a white pages listing that is a database providing for each entry, information such as name and civic address. The particular heuristics model selected to generate the orthography set for each entry combines different words from the various database fields to produce individual orthographies having different levels of expansion, i.e., containing different informations. In a very specific example, one orthography may consist of the first word of the name field. Another orthography may consist of the full name of the entity. Yet, another orthography may be formed by associating the full name and some elements of the civic address, such as the street name. In most instances, each orthography of a given set will share at least one word with another orthography of the set. This, however, is not a critical feature of the invention as it is very well possible to develop heuristics models that produce an orthography set where no common word is shared between a certain pair of orthographies. 
     The list containing the entity identifiers is in a computer readable format so it may be processed by a computer programmed with the selected heuristics model to generate the speech recognition vocabulary. The particular format in which the various words forming the entity identifiers are stored or represented in the computer readable medium is not critical to the invention. 
     In another embodiment of the invention the entity identifier includes title information in addition to the name and civic address data. The title information is used by the particular heuristics model to develop orthographies that contain the title of the particular entity. In a specific example, an entity identifier may include the following information elements: 
     
         ______________________________________                                    
FULL NAME  STREET      NUMBER   LOCALITY                                  
______________________________________                                    
Little Red Bottomo     987      Sunshine                                  
Cars                            Beach                                     
______________________________________                                    
 
    
     After applying the following heuristics model; 
     Full Name 
     Full Name+Street 
     Full Name+Locality 
     Full Name+Street+Locality 
     The set of orthographies will be as follows: 
     Little Red Cars 
     Little Red Cars on Bottomo 
     Little Red Cart in Sunshine Beach 
     Little Red Cars on Bottomo in Sunshine Beach 
     In a different example the entity identifier includes the following information elements: 
     
         ______________________________________                                    
FULL NAME                                                                 
         STREET    NUMBER    LOCALITY TITLE                               
______________________________________                                    
Bill Titus                                                                
         Smart     1234      Montreal Attorney                            
______________________________________                                    
 
    
     After applying the following heuristics model: 
     Full Name 
     Full Name+Street 
     Full Name+Locality 
     Full Name+Street+Locality 
     Full Name+Title 
     Full Name+Title+Street 
     The set of orthographies will be as follows: 
     Bill Titus 
     Bill Titus on Smart 
     Bill Titus in Montreal 
     Bill Titus on Smart in Montreal 
     Bill Titus Attorney 
     Bill Titus Attorney on Smart 
     In the above examples it will be noted that the orthographies in each set share among them at least one common word, namely &#34;Little&#34;, &#34;Red&#34; and &#34;Cars&#34; for the earlier example, while in the latter example &#34;Bill&#34; and &#34;Titus&#34; are common words. 
     The heuristics model used to generate the orthography sets may be simple or of a more complex nature. For example, the model may be such as to generate a first orthography based on the first word in the entity identifier and a second orthography that is a combination of the first and second words of the identifier. For example, the entity identifier &#34;Computer Associates company&#34; will generate by applying this heuristics model the first orthography &#34;Computer&#34;, a second orthography &#34;Computer Associates&#34;, etc. This model can be refined by ignoring certain words that may be meaningless by themselves. Words such as &#34;First&#34;, &#34;The&#34;, do not convey sufficient information when used alone. Thus, to avoid the introduction of orthographies unlikely to lead to correct automation no orthographies based solely on these individual words are used. In those circumstances the first orthography will comprise at least a pair of words. For example &#34;The first machine industry&#34; will generate the orthographies &#34;First machine&#34;, &#34;First machine industry.&#34; etc. 
     As embodiment and broadly described herein the invention also provides an apparatus for generating a speech recognition vocabulary for use in a speech recognition system, said apparatus comprising: 
     first memory means for holding a listing of a plurality of entity identifiers, each entity identifier including at least one word that symbolizes a particular meaning, said plurality of entity identifiers being distinguishable from one another based on either one of individual words and combinations of individual words, at least some of said entity identifiers including at least two separate words; 
     a processor in operative relationship with said first memory means; 
     a program element providing means for generating for each one of said at least some of said entity identifiers an orthography set including a plurality of orthographies, each orthography in a given set being a composition of different words and at least one of said different words being selected from a respective entity identifier. 
     As embodied and broadly described herein the invention further provides machine readable medium containing a program element for instructing a computer to generate a speech recognition vocabulary for use in a speech recognition system, said computer including; 
     first memory means for holding a listing of a plurality of entity identifiers, each entity identifier including at least one word that symbolizes a particular meaning, said plurality of entity identifiers being distinguishable from one another based on either one of individual words and combinations of individual words, at least some of said entity identifiers including at least two separate words; 
     a processor in operative relationship with said first memory means; 
     program element providing means for generating for each one of said at least some of said entity identifiers an orthography set including a plurality of orthographies, each orthography in a given set being a composition of different words and at least one of said different words being selected from a respective entity identifier. 
     As embodied and broadly described herein the invention also provides a machine readable medium containing a speech recognition vocabulary generated by the above described method or apparatus. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a white pages listing entry corresponding to a business organization; 
     FIG. 2 is a general flow chart of the process for expanding abbreviation in the white pages listing; 
     FIG. 3 is a functional block diagram of an apparatus for generating a speech recognition vocabulary from a white pages listing; and 
     FIG. 4 is a general flow chart of the process for generating the speech recognition vocabulary from a white pages listing. 
    
    
     DESCRIPTION OF A PREFERRED EMBODIMENT 
     As an introductory comment it should be pointed out that the invention does not directly relate to the structure and operation of an automated directory assistance system. Rather, the invention is concerned with a method and apparatus for generating a speech recognition vocabulary that can be used in a speech recognition system, such as an automated directory assistance system from a listing of entities potentially recognizable or identifiable by the speech recognition system. For more information on the structure and detailed operation of an automated directory assistance system the reader may refer to the following documents whose contents are hereby incorporated by reference. 
     
         ______________________________________                                    
U.S. PATENTS                                                              
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5,488,652         Gregory, J. Bielby et al.                               
4,164,026         Dubnowski et al.                                        
4,761,737         Gerson et al.                                           
4,797,910         Daudelin                                                
4,959,855         Daudelin                                                
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5,050,215         Nishimura                                               
5,052,038         Shepard                                                 
5,091,947         Ariyoshi et al.                                         
5,097,509         Lennig                                                  
5,127,055         Larlosy                                                 
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5,088,479         Taloanaga et al.                                        
______________________________________                                    
 
    
     
         __________________________________________________________________________
PRIOR ART                                                                 
TITLE          AUTHOR  SOURCE                                             
__________________________________________________________________________
Dynamic Adaptation of Hidden                                              
                       1989, IEEE International Symposium on Circuits     
Markov Model for Robust Speech                                            
                       and Systems vol. 2, May 1989 pp. 1338-1339         
Recognition                                                               
Dynamic Modification of the                                               
                       IBM Technical Disclosure Bulletin, vol. 27, No.    
                       7A,                                                
Vocabulary of a Speech Dec. 1954                                          
Recognition Machine                                                       
Adaptive Acquisition of                                                   
               Gonn et al.                                                
                       Computer Speech and Language, vol. 5, No. 2        
Language               Apr. 1991, London, GB, pp. 101-132                 
Automated Bilingual Directory                                             
               Lenning et al.                                             
                       IEEE Workshop on Interactive Voice Technology      
Assistance Trial In Bell Canada                                           
                       for Telecon Application, Piscataway.               
                       NJ. Oct, 1992.                                     
Unleashing the Potential of                                               
               Labov and                                                  
                       Telesis, Issue 97, 1993, pp. 23-27                 
               Lennig.                                                    
Human-To-Machine                                                          
Communication                                                             
An introduction To Hidden                                                 
               Rabiner and                                                
                       IEEE ASSP Magazine, Jan. 1966, pp. 4-16            
Markov Models  Juang                                                      
Putting Speech Recognition to                                             
               Lennig. Computer, published by IEEE Computer Society,      
Work In The Telephone Network                                             
                       vol 23, No. 8, Aug. 1990                           
Flexible Vocabulary Rocognition                                           
               Lennig et al.                                              
                       IEEE Workshop on Interactive Voice Technology      
of Speech Over The Telephone                                              
                       for Telecom Applications, Piscataway, NJ, Oct.     
                       1992                                               
Mobile Robot Control by a                                                 
                       Nagata et al. pp. 69-76, 1989                      
Structural Hierarchical Neural                                            
Network                                                                   
Large Vocabulary Continuous                                               
               Steven Young                                               
                       IEEE Automatic Speech Recognition Workshop,        
Speech Recognition: a Review                                              
                       September 16, 1995                                 
Putting Speech Recognition to                                             
               Mathew Lennig                                              
                       IEEE (August 1990) reprinted from Computer         
Work in the Telephone Network                                             
__________________________________________________________________________
 
    
     The raw data input to the speech recognition dictionary builder is, as mentioned earlier, an electronic version of the white pages. The electronic white pages provide detailed listing information, analogous to the printed version of the white pages. A sample listing is given below: 
     
         ______________________________________                                    
MICROWAVE ANALYSIS INSTITUTE OF COLORADO                                  
Office Locations                                                          
______________________________________                                    
5800 E Eldridge Av DENVER 3038220396                                      
6169 S Beacon Wy LITTLETON 3032883963                                     
6402 Galbraith WESTMINSTER 3030579821                                     
200 W County Line Rd HIGHLANDS RANCH 3034492001                           
2020 Wadsworth Blvd LAKEWOOD 3039924286                                   
Business Office 5800 E Eldridge Av DENVER 3038221423                      
Analysis Lab 5800 E Eldridge Av DENVER 30362212512                        
Day Or Night Call DENVER 3036224455                                       
______________________________________                                    
 
    
     FIG. 1 graphically illustrates the structure of this business organization. The electronic representation of this sample listing is given in the following table: 
     
         __________________________________________________________________________
ID                          BUILDING                                      
                                  STREET              TELEPHONE           
NUMBER                                                                    
      RANK  NAME      LOCALITY                                            
                            NUMBER                                        
                                  PREFIX                                  
                                        STREET TYPE                       
                                                STREET                    
                                                      NUMBER              
__________________________________________________________________________
33330 0     Microwave Analysis                                            
                      Denver                                              
            Institute of Colorado                                         
33331 1     Office Locations                                              
33332 2               Denver                                              
                            5600  E     AV      Eldridge                  
                                                      3036220396          
33333 2               Littleton                                           
                            6169  S     WY      Beacon                    
                                                      3032833963          
33334 2               Westminster                                         
                            8402                Galbraith                 
                                                      3030579821          
33335 2               Highlands                                           
                            200   X     RD      Country                   
                                                      3034492001          
                      Ranch                     Lane                      
33336 2               Lakewood                                            
                            2020        BLVD    Wadsworth                 
                                                      5039924286          
33337 1     Business Office                                               
                      Denver                                              
                            5900  E     AV      Eldridge                  
                                                      3036221423          
33338 1     Analysis Lab                                                  
                      Denver                                              
                            5800  E     AV      Eldridge                  
                                                      3036221251          
33339 1     Day or Night Call                                             
                      Denver                          3036224455          
__________________________________________________________________________
 
    
     Each white pages caption set can be represented as a &#34;tree&#34; structure, as shown in the above table: the top-line listing is the root of the tree, and the sub-listings are nodes of the tree. The structure embedded in the white pages caption set specifies the topology of the caption set tree. 
     It should be noted that the various fields for each record are merely examples of the type of information that is available. The following table provides a more complete, although not exhaustive list of the various fields of information. 
     
         ______________________________________                                    
FIELD              EXAMPLE                                                
______________________________________                                    
surname field      &lt;kubrick&gt;                                              
subsequent name field                                                     
                   &lt;stanley&gt;                                              
professional title &lt;doctor&gt;                                               
lineage assigned to name                                                  
                   &lt;lr&gt;                                                   
license, academic degrees                                                 
                   &lt;PhD&gt;                                                  
business description                                                      
                   &lt;master plumber&gt;                                       
building number    &lt;16&gt;                                                   
building number prefix                                                    
                   &lt;N12&gt;                                                  
building number postfix                                                   
                   &lt;A&gt;                                                    
street name        &lt;ammand bombardier&gt;                                    
street directional prefix                                                 
                   &lt;north&gt;                                                
street thoroughfare type                                                  
                   &lt;boulevard&gt;                                            
street directional postfix                                                
                   &lt;east&gt;                                                 
Locality           &lt;saint lambert&gt;                                        
state or province  &lt;part&gt;                                                 
county             &lt;montenegia&gt;                                           
______________________________________                                    
 
    
     VOCABULARY BUILDER 
     This section describes methods of building the speech recognition lexicon. The lexicon is later phonemically transcribed, mapped into a set of acoustic models, and a speech recognition dictionary is created. Each lexical item, or phrase, attempts to mimic the manner in which directory assistance queries are made. Phrases are generated using heuristics. More specifically, heuristics generate recognition phrases using the text contained in the electronic white pages. However, before processing the white pages entries with heuristics to create the speech recognition lexicon, the white pages data is pre-processed which corresponds to a &#34;cleaning operation&#34;, involving the expansion of abbreviations and the removal of non-productive information. 
     The expansion of abbreviations is effected by using a substitution table. The program which generates the orthographies from the white pages listing observes a number of fields in the listing for occurrences of specific letter combinations known to be abbreviations. 
     
         ______________________________________                                    
         COMBINATION OF                                                   
FIELD    LETTERS        SUBSTITUTED WORD(S)                               
______________________________________                                    
Name     agcy           agency                                            
Title    atty           attorney                                          
         MD             Doctor                                            
Street Prefix                                                             
         S              south                                             
         N              north                                             
         E              east                                              
         W              west                                              
Locality Bouldr         Boulder                                           
         Mt1            Montreal                                          
______________________________________                                    
 
    
     This table provides only an example of possible abbreviations and the substituted words that the system can use. In practice, the expansion of the abbreviations is not a complex operation because what the program is looking for, namely the different abbreviations are usually known in advance as they are established actuating to a standard practice of the telephone company. Moreover, the database fields where the abbreviations are likely to be found are usually also known. Thus, it suffices to scan the white pages database looking for the all possible abbreviations. Once an abbreviation is located a substitution table is consulted to find the expansion corresponding to the given abbreviation. That expansion is then inserted in place of the original abbreviation. This process is illustrated in FIG. 2 of the drawings. The program element responsible for the expansion of abbreviations searches at step 10 possible abbreviations that are known in advance in the fields of the database where those abbreviations are likely to be found. When an abbreviation is located at step 12, a substitution table is consulted at step 14 to determine the substitution word. The latter is then inserted at step 16 in the database. The program next fetches the next record of the database and the process repeated until all the records have been examined. 
     The final step of the &#34;cleaning operation&#34; consists of removing extraneous information that is non-productive in the sense it does not provide any additional information about the particular entity. This process is also effected by scanning the white pages listing database and looking for particular letter combinations or key words. Once such letter combination or key word is located, it is simply erased. Examples of what is considered non-productive information is as follows: &#34;Toll free number&#34;, &#34;24 hour service&#34;, &#34;Day or night surface&#34;, among any other possible letters or words that may be considered superfluous. This operation is effected by using a program element of the type illustrated in FIG. 2. Each field of the database is scanned to locate pre-determined words or phrases and when one of these words or phrases is located it is erased. 
     The heuristics model used to generate the orthographies of the speech recognition lexicon may vary with the intended application. For example, the heuristics for a simple listing can be as follows: 
     First word in name field 
     Full name field 
     Full name field and street name 
     Full name field street name less street thoroughfare type information etc. 
     For example, consider the following entity identifier: 
     
         ______________________________________                                    
TYPE OF DATA     DATA                                                     
______________________________________                                    
ID Number        28724                                                    
Full Name        ABC American Ship Building                               
                 Company                                                  
Building Number  909                                                      
Street           Wadsworth                                                
Street Type      BLVD                                                     
Telephone Number 5146766656                                               
______________________________________                                    
 
    
     Application of the heuristics model (described above) generates the following orthography set: 
     ABC 
     ABC American Ship Building Company 
     ABC American Ship Building Company on Wadsworth Boulevard 
     ABC American Ship Building Company on Wadsworth 
     This orthography set includes four individual orthographies each one pointing toward the same telephone number. The first two orthographies contain words related only to the name of the entity, while the last two orthographies are a combination, in other words including information relating to the name of the entity and to the civic address. The word &#34;ABC&#34; is common to all orthographies. 
     Although this heuristics model is simple, it may sometimes create orthographies that are not likely to match what the user is saying. In some instances, the first word alone in the name field of the entity name may by itself be meaningless. For example in the business &#34;First American ship building company&#34;, an orthography containing solely the word &#34;First&#34; may not be very useful because it is unlikely that the user will request the telephone number of that company solely by saying &#34;First&#34;. Thus, the model can be refined in two possible ways. One is to identify those non-productive words in an entity name and when a word in the preestablished group is encountered it is not considered. In this example, the program building the speech recognition vocabulary looks for &#34;First&#34; at the beginning of the name and if that word is found it is ignored and only the second word in the name is used to build the first orthography in the set. The second possibility is to create orthographies that include at least a pair of words from the name of the entity, namely the first and the second words. If this heuristics model is applied to the example given above, an orthography set including only three orthographies will be generated, excluding the orthography &#34;ABC.&#34; 
     The table below provides an example of a caption set that is related to a hierarchical organizational structure of the type illustrated in FIG. 1. The heuristics model used to generate the orthography groups also takes into account the rank number field in the white pages database that provides information as to whether the entry is at a root level or constitutes a branch. 
     
         __________________________________________________________________________
ID                          BUILDING                                      
                                  STREET               TELEPHONE          
NUMBER                                                                    
     RANK NAME       LOCALITY                                             
                            NUMBER                                        
                                  PREFIX                                  
                                        STREET TYPE                       
                                                STREET NUMBER             
__________________________________________________________________________
28724                                                                     
     3    First American Ship                                             
          Building Company                                                
28725                                                                     
     1    Accounts and Personnel                                          
                            909         BLVD    Wadsworth                 
                                                       2343459067         
28726                                                                     
     1    Arvada Office     4851                Independence              
                                                       2343455077         
29727                                                                     
     1    Aurora Office     2851  S     RD      Parker 2345459022         
__________________________________________________________________________
 
    
     The following heuristics model will generate the orthography group below: 
     First two words in &#34;Rank 0&#34; name field 
     Full &#34;Rank 0&#34; name field 
     Full &#34;Rank 0&#34; name field and full &#34;Rank 1&#34; name field 
     Full &#34;Rank 0&#34; name field and full &#34;Rank 1&#34; street name 
     Full &#34;Rank 0&#34; name field and &#34;Rank 1&#34; street name less street thoroughfare type information etc. 
     First American 
     First American Ship Building Company 
     First American Ship Building Company-Accounts and Personnel 
     First American Ship Building Company-Wadsworth Boulevard 
     First American Ship Building Company-Wadsworth 
     Listings with title information are treated with different heuristics. The title field in the white pages entry is used to store information relating to the profession of the person specified in the name field. Titles include orthopedic surgeons, judges, attorneys, senators, doctors, and dentists. Titles are interpreted using a substitution table. For example, the title &#34;MD OB-GYN &amp; INFERTILITY&#34; is interpreted as &#34;Doctor&#34;. A common variant of the usage of title information has been observed: the title can occur in the final position of the phrase. For example, the title at initial position &#34;Dr.&#34; becomes &#34;MD&#34; at final position, and phrase initial title &#34;Attorney&#34; becomes phrase final &#34;Attorney at Law&#34;. As an example, the following heuristics may be applied to titled listings: 
     TITLE+SUBSEQUENT NAME FILED+SURNAME FIELD 
     TITLE+SURNAME FIELD 
     SUBSEQUENT NAME FIELD+SURNAME FIELD 
     SURNAME FIELD 
     SUBSEQUENT NAME FIELD+SURNAME FIELD+TITLE 
     For example, the listing &lt;Surname Field: Trine&gt;, &lt;Subsequent Name Field: William A&gt; and &lt;Title: Atty&gt;&#34; will generate the following set of orthographies all pointing toward the same telephone number: 
     Attorney William A Trine 
     Attorney Trine 
     William A Trine 
     Trine 
     William A Trine, Attorney at Law 
     The above described heuristics models are merely examples of a large number of different possibilities. In general, the heuristics model chosen for the particular application is designed to mimic the way people formulate requests. Simple heuristics models have the advantage of generating a lesser number of orthographies. On the down side, however, they may lead to a less than perfect automation rate because the automated telephone directory assistance system may not be able to recognize all reasonably formulated requests. More refined heuristics models generate a larger number of orthographies that cover more possibilities in terms of request formulations, however these models significantly increase the size of the speech recognition vocabulary which is an important element if one desires to provide real time performance. Thus, the specific heuristics model used to generate the speech recognition vocabulary will need to be adapted to the particular application and may greatly vary from one case to another. In some instances, a single heuristics model may be sufficient for the entire vocabulary generation. In other applications, a combinations of heuristics models may need to be used in dependence of the type of white pages entries to be processed. For example, it the white pages listings contain both single line entries and caption sets it could be advantageous to use different heuristics models applicable to each type of entry. 
     The apparatus for generating the speech recognition vocabulary is illustrated in FIG. 3. The apparatus includes a processor 18 in operative relationship with a memory having three segments, namely a first segment 20 containing program instructions, a second segment 22 containing white pages listing, and a third segment 24 containing the speech recognition vocabulary. The flow chart illustrating the program operation is shown in FIG. 4. At step 26 a database record is fetched. At step 28 the desired heuristics model invoked and at step 30 the set of orthographies generated. The set of orthographies are then placed in the third memory segment 24. The speech recognition vocabulary my then be recorded on mass storage 32, if desired. 
     Next, a dictionary access program of the type known in the art is invoked to generate a &#34;phonemic&#34; transcription for each orthography in the vocabulary. A phonemic transcription is an expressive representation of the sound patterns of a phrase using a set of 41 phoneme symbols (1 symbol for each distinct sound in the English language). This phonemic transcription is transformed into articulatory transcriptions (surface forms), which capture special articulatory phenomena that depend on the context of a phoneme. Then, an acoustic transcription is generated, indicating which acoustic model (represented as a concise mathematical model) should be used during speech recognition. The vocabulary thus transcribed can now be processed by the speech recognition layer of the automated directory assistance system. 
     The above description of a preferred embodiment should not be interpreted in any limiting manner since variations and refinements can be made without departing from the spirit of the invention. For instance, although an example of the invention has been provided above with strong emphasis on an automated directory assistance system, the method and apparatus for generating the speech recognition vocabulary could also be used in other types of speech recognition systems. The scope of the invention is defined in the appended claims and their equivalents.