Abstract:
There is provided a voice Interactive system for inputting user&#39;s voice information, conducting voice recognition with respect to the voice information, analyzing the contents of the voice information, controlling a transmission path of the voice information in accordance with the contents of the voice information, outputting a synthesized voice, extracting the contents of a response corresponding to the voice information by referring to a knowledge database, and creating the synthesized voice in accordance with the contents of a response, wherein in the case where it is monitored at all times whether or not use&#39;s interaction is being smoothly conducted, and when it is determined that the user&#39;s interaction is not being smoothly conducted, a third-party user is allowed to participate,as a helper, in the users interaction.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a voice interactive system and a voice interactive method for allowing a voice interactive system to smoothly function, in which a user realizes various functions by interaction with synthesized voice generated by the system. 
   2. Description of the Related Art 
   Recently, due to the enhancement of a computer processing speed, the enlargement of an information capacity that can be used, and the rapid advancement of a voice recognition technique, voice recognition at a word level can be put into practical use without any problem. Therefore, a voice recognition technique is also becoming one of important techniques for configuring a system. The use of such a voice recognition technique enables various problems to be solved by using a voice interactive interface utilizing only a voice without a high-level graphical interface. 
   As described above, a voice interactive system is being developed in various fields, which allows a user to solve problems in the user&#39;s intended order by the use of a voice interactive interface, and which allows the ability of oral communication owned by a human to be fully taken advantage of. 
     FIG. 1  shows a configuration of a conventional voice interactive system. In  FIG. 1 , reference numeral  1  denotes a voice input part through which a user inputs voice information. As an input medium, file transfer for a web file and the like, as well as a microphone, can be contemplated. The input voice information is sent to a voice recognition part  2  through a network  7  or the like. As the network  7 , various connection forms such as the Internet and WAN/LAN can be contemplated. 
   Reference numeral  2  denotes a voice recognition part that analyzes the contents of the input voice information. It is also considered that the voice recognition part  2  has a noise reduction function for the purpose of preventing problems in the case where the input voice contains noise. 
   Reference numeral  6  denotes a voice output part that outputs a response to the voice input from the voice input part  1  as a synthesized voice. An output method is not limited to an output based on a voice, and the contents of a response may be displayed on a display apparatus. 
   Reference numeral  3  denotes a voice information mediation part, which controls a response timing among the voice input part  1 , the voice output part  6 , and an interaction engine  4 . Reference numeral  4  denotes an interaction engine, which refers to a knowledge database  5  in accordance with the contents of the input voice to extract the most suitable contents of a response. Therefore, the performance of the interaction engine  4  directly influences the performance of the voice interactive system. 
   However, in the above-mentioned conventional voice interactive system, a current voice recognition technique has not reached a level with a 100% recognition precision. Therefore, the intention of user&#39;s uttered voice may not be sufficiently recognized. Furthermore, even with the interaction engine  4  having high performance, it is impossible to completely handle human daily conversation, and it is easily expected that conversation with the contents that cannot be handled by such an interaction engine is conducted. 
   In the above-mentioned case, it is considered that the conversation that cannot be handled only by the interaction engine  4  may be handled by allowing a third-party user or an operator who is familiar with the contents of the conversation to participate therein as a helper. 
   For example, JP 7(1995)-19239 B discloses a system that allows a user to interact with an operator (i.e., a third-party user) when detecting that a particular word is contained in an input voice. 
   Furthermore, JP 8(1996)-76965 A discloses a voice recognition system in which a user can request mediation of an operator when the user is at a loss how to use the system. JP 10(1998)-124086 A discloses a voice interactive system that allows a system supporter to directly respond to an input voice in the case where an expert system alone cannot respond thereto. 
   However, according to the invention disclosed, for example, in JP 7(1995)-19239 B, the case is also assumed where operator&#39;s help is required even if a particular word is not contained in an input voice. Furthermore, it is practically difficult to extract words on the assumption of various cases. Therefore, it is actually difficult to configure such a system. 
   According to the invention disclosed in JP 8(1996)-76965 A, a user cannot get operator&#39;s help without the user&#39;s intention. Therefore, regarding interactive contents that would be easily determined to be useless under the supervision of a third-party user, operator&#39;s help can be provided only after a considerable period of time. 
   According to the invention disclosed in JP 10(1998)-124086 A, only in the case of interaction that is not contained in a rule database in an expert system, help of a system supporter can be provided. If a knowledge level of a user is not matched with a knowledge level of a rule database, even interaction contained in the rule database cannot be conducted smoothly, which makes it difficult for a user to understand the interaction. 
   SUMMARY OF THE INVENTION 
   Therefore, with the foregoing in mind, it is an object of the present invention to provide a voice interactive system and a voice interactive method, capable of automatically controlling a timing at which an operator mediates in accordance with a knowledge level of a user. 
   In order to achieve the above-mentioned object, a voice interactive system of the present invention includes: a voice information input part for inputting user&#39;s voice information from a user terminal; a voice recognition part for conducting voice recognition with respect to the voice information, and analyzing contents of the voice information; a voice information mediation part for controlling a transmission path of the voice information in accordance with the contents of the voice information; an interaction engine for extracting contents of a response corresponding to the voice information by referring to a knowledge database, and creating a synthesized voice in accordance with the contents of a response; and a voice information output part for outputting the synthesized voice, wherein the voice information mediation part monitors at all times whether or not the user&#39;s interaction is being smoothly conducted, and in a case of determining that the user&#39;s interaction is not being smoothly conducted, allows a third-party user to participate in interaction between the user and the interaction engine from another terminal as a helper. 
   Because of the above-mentioned configuration, even in the case where there is a large difference between a knowledge level of a knowledge database and a knowledge level of a user, a timing at which operator&#39;s help is provided can be automatically controlled. 
   In the voice interactive system of the present invention, it is preferable that the voice information mediation part determines whether or not the user&#39;s interaction is being smoothly conducted based on whether or not an accumulation value of the number of times at which the contents of a response are not found in the knowledge database exceeds a set limit number, and in a case where the accumulation value exceeds the set limit number, allows a third-party user to participate in the interaction between the user and the interaction engine from another terminal as a helper. The reason for this is as follows. Even when an item of interest is not found in the knowledge database at the first attempt, operator&#39;s help is not necessarily required immediately; however, in the case where appropriate items are not hit as a response even after some trial and error, operator&#39;s help is required. 
   In the voice interactive system of the present invention, it is preferable that the voice information mediation part determines whether or not the user&#39;s interaction is being smoothly conducted based on an average reaction time from a response of the interaction engine to a reaction of the user, and in a case where the average reaction time exceeds a first threshold value or in a case where the average reaction time is below a second threshold value, allows a third-party user to participate in the interaction between the user and the interaction engine from another terminal as a helper. A user&#39;s average reaction time is within a predetermined range while interaction is being smoothly conducted. However, when interaction becomes redundant, a reaction time is likely to become short gradually. On the other hand, when the user cannot follow the contents of interaction, a reaction time is likely to become long gradually. Therefore, such properties peculiar to interaction are utilized. 
   In the voice interactive system of the present invention, it is preferable that the voice information mediation part determines whether or not the user&#39;s interaction is being smoothly conducted based on an evaluation value of average sound quality of the voice information input by the user, and in a case where the evaluation value of average sound quality exceeds a first threshold value or in a case where the evaluation value of average sound quality is below a second threshold value, allows a third-party user to participate in the interaction between the user and the interaction engine from another terminal as a helper. An average value of a pitch or the like of a voice input by a user is within a predetermined range while interaction is being smoothly conducted. When interaction becomes redundant, an average value of a pitch as well as a voice pitch is likely to become high gradually. On the other hand, when a user cannot follow the contents of interaction, an average value of a pitch as well as a voice pitch is likely to become low gradually. Therefore, such properties peculiar to interaction are utilized. 
   In the voice interactive system of the present invention, it is preferable that the voice information mediation part determines a progress of interaction in accordance with an interaction time from a beginning of the user&#39;s interaction and the number of accesses to the interaction engine, and a participation form of the third-party user is successively changed, in an increasing order of the progress of interaction, from involvement in which the contents of interaction with the user is displayed to the third-party user and the contents of interaction is updated by the third-party user, parallel input in which the third-party user conducts an input in parallel with the user, to switching in which the third-party user directly interacts with the user. This is because help is provided in accordance with a level required by a user. 
   In the voice interactive system of the present invention, the interaction engine further includes an interaction history information storage part for recording interaction history on a user basis, and a helper selection part for selecting the third-party user that is considered to be most familiar with the contents of the interaction from the interaction history as a helper, and the helper most appropriate for contents of the voice information is selected. Because of this configuration, in accordance with the contents of interaction, an appropriate user among those having participated in interaction, as well as an operator specialized in helping, can be selected. 
   The voice interactive system of the present invention further includes a help request notification part for, in a case where the voice information mediation part determines that the user&#39;s interaction is not being smoothly conducted, notifying a third-party helper user of such a fact, wherein in a case where the help request notification part notifies the third-party helper user of the fact that the user&#39;s interaction is not being smoothly conducted, the third-party helper user is capable of voluntarily interacting with the user, and in a case where it is detected that only a voice of the third-party helper user continues for a predetermined period of time or longer in interaction between the third-party helper user and the user, the interaction engine interacts only with the third-party helper user. Because of this configuration, an operator specialized in helping is provided with a chance of voluntarily helping a user with interaction. Furthermore, by detecting that the operator specialized in helping takes the initiative in interaction, it is considered that interaction proceeds more smoothly when the operator specialized in helping is allowed to directly interact with the interaction engine. 
   The voice interactive system of the present invention further includes an interaction history display part for displaying the interaction history stored in the interaction history information storage part to a third-party helper user, and a helper instruction part for receiving a help instruction from the third-party helper user, wherein when the help instruction part receives the help instruction from the third-party helper user, the voice information mediation part enables the interaction between the third-party helper user and the user to be conducted, and when a degree of help of the third-party helper user exceeds a predetermined threshold value in interaction between the third-party helper user and the user, the interaction engine interacts only with the third-party helper user. Because of this configuration, an operator specialized in helping is provided with a chance of voluntarily helping a user with interaction. Furthermore, by detecting that the operator specialized in helping takes the initiative in interaction, it is considered that interaction proceeds more smoothly when the operator specialized in helping is allowed to directly interact with the interaction engine. 
   Furthermore, the present invention is characterized by software for executing the function of the above-mentioned voice interactive system as processing of a computer. More specifically, the present invention is characterized by a voice interactive method including: inputting user&#39;s voice information from a user terminal; conducting voice recognition with respect to the voice information, and analyzing contents of the voice information; controlling a transmission path of the voice information in accordance with the contents of the voice information; and outputting a synthesized voice, in the controlling of a transmission path of the voice information, contents of a response corresponding to the voice information being extracted by referring to a knowledge database, and a synthesized voice being created in accordance with the contents of a response, wherein in the controlling of a transmission path of the voice information, it is monitored at all times whether or not the user&#39;s interaction is being smoothly conducted, and in a case where it is determined that the user&#39;s interaction is not being smoothly conducted, a third-party user is allowed to participate in interaction between the user and the interaction engine from another terminal as a helper, and a computer program storing these operations. 
   Because of the above-mentioned configuration, by loading the program onto a computer for execution, even in the case where there is a large difference between a knowledge level of a knowledge database and a knowledge level of a user, a timing at which operator&#39;s help is provided can be automatically controlled. 
   These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a configuration of a conventional voice interactive system. 
       FIG. 2  shows a configuration of a voice interactive system of an embodiment of the present invention. 
       FIG. 3  is a flow chart illustrating processing in the voice interactive system of the embodiment of the present invention. 
       FIG. 4  schematically shows how to determine a help level. 
       FIG. 5  shows a configuration of the voice interactive system of an embodiment of the present invention. 
       FIG. 6  shows a configuration of the voice interactive system of an embodiment of the present invention. 
       FIG. 7  illustrates a computer environment. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Hereinafter, a voice interactive system of an embodiment of the present invention will be described with reference to the drawings.  FIG. 2  shows a configuration of the voice interactive system of the embodiment of the present invention. The same components as those in  FIG. 1  are denoted with the same reference numerals as those therein. The detailed description thereof will be omitted here. 
   A substantial difference between the voice interactive systems shown in  FIGS. 1 and 2  lies in that an interaction management part  21  is provided in the system shown in  FIG. 2  so as to monitor a user&#39;s interaction situation at all times. The interaction management part  21  obtains interaction history information while monitoring user&#39;s interaction, and stores the information in an interaction history information storage part  22 . 
   The interaction history information includes the contents of interaction recognized by a voice recognition part  2  on a user basis, a time required for a user to respond to interaction, a reaction time up to a user responds to interaction, information on sound quality such as the pitch of an input voice, an accumulation value of the number of hits that are not found in a knowledge database  5  as information obtained through a voice information mediation part  3 , and the like. 
   An accumulation time from the beginning of user&#39;s interaction is calculated from a user&#39;s response time, and an average value of the pitch or the like of an input voice is calculated on the basis of a user&#39;s input voice. Based on these results, including the accumulation value of the number of hits that are not found in the knowledge database  5 , and the like, it is possible to determine whether or not user&#39;s interaction is being smoothly conducted, to check on the progress of interaction, and the like. 
   The voice information mediation part  3  is provided with a function of activating an operator terminal connection part  23  as a new function. The voice information mediation part  3  determines whether or not predetermined conditions are satisfied. In the case where the predetermined conditions are satisfied, the voice information mediation part  3  determines that user&#39;s interaction is not being smoothly conducted, to allow the operator terminal connection part  23  to be connected to an operator terminal for helping user&#39;s interaction. 
   As the predetermined conditions to be determined, various conditions are considered. First, whether or not user&#39;s interaction is being smoothly conducted is determined based on whether or not an accumulation value of the number of times at which items appropriate as the contents of a response are not registered in the knowledge database  5  (i.e., the number of hits that are not found in the knowledge database  5 ) exceeds a set limit number. 
   More specifically, in the case where items appropriate as the contents of a response are not registered, a response for urging a user to do another input is made. After some trial and error, appropriate items may be hit as a response. Therefore, even when an item of interest is not found at the first attempt, operator&#39;s help is not necessarily required immediately. On the other hand, in the case where appropriate items are not hit as a response even after some trial and error, operator&#39;s help is required. Thus, in the case where the number of hits that are not found is accumulated, and the accumulation value exceeds a predetermined threshold value, the operator terminal connection part  23  is activated to be connected to an operator terminal so that an operator can participate in user&#39;s interaction. 
   Whether or not user&#39;s interaction is being smoothly conducted may also be determined based on an average reaction time on a user&#39;s response basis, calculated from the interaction history information stored in the interaction history information storage part  22 . 
   More specifically, a user&#39;s reaction time is within a predetermined range while interaction is being smoothly conducted. However, when interaction becomes redundant, a reaction time is likely to become short gradually. When the user cannot follow the contents of interaction, a reaction time is likely to become long gradually. Utilizing such properties peculiar to interaction, in the case where an average reaction time exceeds a predetermined threshold value that is an upper limit of a reaction time in ordinary interaction, or in the case where an average reaction time is below a predetermined threshold value that is a lower limit of a reaction time in ordinary interaction, the operator terminal connection part  23  is activated to be connected to an operator terminal so that an operator can participate in user&#39;s interaction. 
   Furthermore, whether or not user&#39;s interaction is being smoothly conducted may also be determined based on an average pitch or the like of voice information input by a user, calculated from the interaction history information stored in the interaction history information storage part  22 . 
   More specifically, an average value of a pitch or the like of a voice input by a user is within a predetermined range while interaction is being smoothly conducted. When interaction becomes redundant, an average value of a pitch as well as a voice pitch is likely to become high gradually. When a user cannot follow the contents of interaction, an average value of a pitch as well as a voice pitch is likely to become low gradually. Utilizing such properties peculiar to interaction, in the case where an average value of a pitch or the like of a voice input by a user exceeds a predetermined threshold value that is an upper limit of an average value of a voice pitch or the like in ordinary interaction, or in the case where an average value of a pitch or the like of a voice input by a user is below a predetermined threshold value that is a lower limit of an average value of a voice pitch or the like in ordinary interaction, the operator terminal connection part  23  is activated to be connected to an operator terminal so that an operator can participate in user&#39;s interaction. 
   Next, a processing flow of a program for realizing the voice interactive system of the embodiment of the present invention will be described.  FIG. 3  is a flow chart illustrating processing of a program for realizing the voice interactive system of the embodiment of the present invention. 
   In  FIG. 3 , when a user inputs a voice (Operation  301 ), the voice is recognized, and the contents of the input voice information are analyzed (Operation  302 ). Then, the results thus obtained are stored as interaction history information (Operation  303 ). Simultaneously, an average reaction time excluding a time of beginning of interaction, and an average value of a voice pitch or the like on an input voice basis are calculated, and similarly stored as interaction history information (Operation  304 ). 
   Next, referring to the knowledge database based on the contents of an input voice (Operation  305 ), if information corresponding to the contents of an input voice is in the knowledge database (Operation  306 : Yes), the contents of a response are automatically generated based on the information, and output as a synthesized voice (Operation  307 ). Thus, interaction is continued. 
   On the other hand, if there is no knowledge corresponding to the contents of an input voice in the knowledge database (Operation  306 : No), a message for urging another input is displayed (Operation  308 ), and this is accumulated in the interaction history information as the number of hits that are not found in the knowledge database (Operation  309 ). 
   Regarding the interaction history information, in the case where an accumulation value of the number of hits that are not found in the knowledge database exceeds a predetermined threshold value (Operation  310 : Yes), it is determined that operator&#39;s help is required, and an operator terminal is connected with the interaction (Operation  311 ). 
   As described above, in the present embodiment, in the case where the difference between a knowledge level of the knowledge database and a knowledge level of a user is large, it is possible to automatically control a timing at which operator&#39;s help is provided. 
   Furthermore, based on the interaction history information stored in the interaction history information storage part  22 , an interaction time from the beginning of user&#39;s interaction and an accumulation value of the number of accesses to the interaction engine  4  can also be obtained. In the case where the interaction time is long, and the accumulation value of the number of accesses to the interaction engine  4  is large, the progress of user&#39;s interaction is considered to be high. 
   A method for allowing an operator to help a user may be changed based on the progress of interaction, using a interaction time and an accumulation value of the number of accesses to the interaction engine  4  as evaluation values. More specifically, as shown in  FIG. 4 , in the case where an interaction time is short, or in the case where an accumulation value of the number of accesses to the interaction engine  4  is small, the progress of interaction is determined to be low, and a method for allowing an operator to determine the necessity of help is considered to be sufficient. 
   Specifically, only in the case where the contents of interaction are displayed at the operator terminal  24  before being output to a user, and an operator determines that some help is needed, the contents of an output may be updated. This is because there is a high possibility that interaction can proceed without an operator by further repetition of accesses to the interaction engine  4 . Such an arbitrary helping method by an operator is referred to as “involvement”. 
   The contents of interaction at the operator terminal  24  are displayed by the interaction history display part  26 , and an operator&#39;s input for help is done with a voice through the voice input part  25 . 
   In the case where an interaction time is accumulated to some degree, or in the case where an accumulation value of the number of accesses to the interaction engine  4  becomes a certain degree of value, it is determined that the progress of interaction is increased to some degree, and more active help by an operator is considered to be required. 
   More specifically, it may be considered that the contents of interaction are displayed to a user as well as the operator terminal  24 , and an operator inputs a new output from the standpoint of a third-party user. In the case where it is determined that interaction is not being conducted smoothly irrespective of whether the progress of interaction has been made to some degree, it is considered that there are insufficient portions only by repetition of accesses to the interaction engine  4 . Such an active helping method by an operator is referred to as “parallel input”. 
   Also in this case, the contents of interaction at the operator terminal  24  are displayed by the interaction history display part  26 , and an operator&#39;s input for help is done with a voice through the voice input part  25 . 
   Furthermore, in the case where a considerable amount of interaction time is accumulated, or in the case where an accumulation value of the number of accesses to the interaction engine  4  is very high, it is determined that the progress of interaction is very high, and active help by an operator is considered to be required. Specifically, it is considered that an operator directly interacts with a user. This is because there is a high possibility that interaction cannot be continued by the accesses to the interaction engine  4 . Such a helping method without using the interaction engine  4  so that an operator can directly provide help is referred to as “switching”. 
   Also in this case, the contents of interaction at the operator terminal  24  are displayed by the interaction history display part  26 , and an operator&#39;s input for help is done with a voice through the voice input part  25 . 
   Thus, strictness and lenience of helping means by an operator can be determined in accordance with the progress of interaction, and operator&#39;s help at a level required by a user can be automatically determined. 
   An operator is not required to be an exclusive operator. For example, an operator may be one of the other users accessing the same application environment on the network, who is familiar with the contents of voice information. In this case, as shown in  FIG. 5 , a helper selection part  51  is required. By referring to the interaction history information storage part  22  storing history of the contents of user&#39;s interaction, the helper selection part  51  selects one of the other users in the interaction regarding the same or similar contents previously conducted, who is considered to be most familiar with the contents. Furthermore, the voice information mediation part  3  determines a connection destination of a user terminal. 
   More specifically, in  FIG. 5 , the voice information mediation part  3  extracts the previously conducted interaction regarding the contents of input voice information by referring to the interaction history information storage part  22 . The helper selection part  51  selects one of the other users, who is considered to be most familiar with the contents. Thus, a selected user terminal connection part  52  is activated to be connected to a terminal of the selected user. 
   At the selected user terminal  53 , the interaction history is displayed by the interaction history display part  55 , and a helping action is conducted through the voice input part  54  in place of an operator with the knowledge of the selected user. 
   Furthermore, based on the interaction history information stored in the interaction history information storage part  22 , it can be detected that a user cannot smoothly proceed interaction by various methods. In this case, an operator may determine to help a user with the interaction. 
   More specifically, as shown in  FIG. 6 , when a user cannot smoothly proceed interaction, an operator terminal connection part  61  is activated to allow a help request notification part  56  to automatically notify an operator of a request for help so that an operator can help the user with the interaction. 
   Alternatively, the following may also be possible. As shown in  FIG. 6 , the operator terminal connection part  61  is activated at all times irrespective of whether it is detected that a user cannot smoothly proceed interaction, and interaction history between the user and the interaction engine is displayed by the interaction history display part  64  at the operator terminal  62 , whereby an operator starts helping at a timing at which the operator determines that help is required. 
   In this case, a help instruction part  65  is further provided. In the case where an operator determines that help is required at the operator terminal  62 , a help instruction input by the operator is received by the help instruction part  65  of the voice information mediation part  3 , and passed to the interaction management part  21 . The interaction management part  21  that has received the help instruction enables interaction between the operator and the user to be conducted, whereby a helping action by an operator becomes possible. 
   Furthermore, in the case where operator&#39;s help is mainly conducted (e.g., in the case where it is detected that the interaction between the user and the interaction engine is hardly conducted, and only interaction between the operator and the interaction engine is conducted), connection may be switched so that only the interaction between the interaction engine and the operator can be conducted. More specifically, in the case where it is detected that a degree of operator&#39;s help exceeds a predetermined threshold value, the connection to the user terminal is disconnected to allow only the interaction with the operator to be conducted, whereby it is attempted to solve the problem immediately. 
   In this case, indexes for determining a situation where operator&#39;s help is mainly conducted include an information transmission amount per unit time, a soundless time ratio per unit time, a speaker exchange frequency per unit time, a ratio of a generation time of an operator and a user per unit time, and the like. The indexes are not particularly limited thereto. Any index may be used as long as it is determined that operator&#39;s help is mainly conducted. 
   In the present embodiment, the interactive system based on an input of a voice has been described. The similar system is also applicable to a text input system such as chatting. In chatting, the contents of interaction to be input with a voice are merely changed to a text input through a keyboard or the like. In this case, as an index for detecting an exchange frequency in chatting, a text data amount input per unit time, a text data amount to be communicated, and the like are considered, which have no substantial difference from the present embodiment. 
   A program for realizing a voice interactive system of the present embodiment of the present invention is stored in not only a portable recording medium  72  such as a CD-ROM  72 - 1  and a flexible disk  72 - 2 , but also another storage apparatus  71  provided at the end of a communication line and a recording medium  74  such as a hard disk and a RAM of a computer  73 , as shown in  FIG. 7 . In execution, the program is loaded onto the computer  73 , and executed on a main memory. 
   Furthermore, interaction history information and the like generated by the voice interactive system of the present embodiment of the present invention is also stored in not only a portable recording medium  72  such as a CD-ROM  72 - 1  and a flexible disk  72 - 2 , but also another storage apparatus  71  provided at the end of a communication line and a recording medium  74  such as a hard disk and a RAM of a computer  73 , as shown in  FIG. 7 . For example, such a recording medium is read by the computer  73  when the voice interactive system of the present invention is utilized. 
   As described above, according to the voice interactive system of the present invention, even in the case where there is a large difference between a knowledge level of a knowledge database and a knowledge level of a user, a timing at which operator&#39;s help is provided can be automatically controlled. 
   Furthermore, according to the voice interactive system of the present invention, the strictness and lenience of helping means by an operator can be determined in accordance with the progress of interaction, and operator&#39;s help at a level required by a user can be automatically determined. 
   The invention may be embodied in other forms without departing from the spirit or essential characteristics thereof The embodiments disclosed in this application are to be considered in all respects as illustrative and not limiting. The scope of the invention is indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.