Patent Publication Number: US-2007124753-A1

Title: Digital broadcast receiving device

Description:
This application is based on application No. 2000-003277 filed in Japan, the content of which is hereby incorporated by reference.  
     BACKGROUND OF THE INVENTION  
      (1) Field of the Invention  
      The present invention relates to digital broadcast reception technology for receiving a repeatedly-transmitted broadcast wave that includes “interactive data”, and for achieving pseudo-interactive communications.  
      (2) Description of the Prior Art  
      In recent years, fee-based television (TV) programs have been broadcasted.  
      Japanese Laid-Open Patent Application No. 11-243535 discloses a digital communication satellite broadcast service. For this communication satellite broadcast service, a plurality of transport streams (hereafter called “TS”) for digital data are broadcasted in parallel. The number of transport streams broadcasted in parallel is equal to a number of transponders. A plurality of transport packets (hereafter “TP”), which contain data corresponding to a plurality of programs, are time-division multiplexed into each TS. A user selects a given program contained in a TS, and watches the program.  
      With a fee-based digital broadcast, a viewing of a program is restricted to predetermined viewers. To restrict viewers, the following method is used.  
      Encryption (hereafter, “scrambling”) is performed separately for each TP (hereafter, “AV (audio-video) TP”) containing video data and audio data for programs. A descrambling key to descramble such scrambled AV TP, and program attribute information for the programs make up program information (hereafter, “ECM”) and are contained in another TP (hereafter, “ECM TP”). Such ECM TP and AV TP are broadcasted together. This ECM TP is also scrambled. A work key to descramble the scrambled ECM TP, and subscription information make up individual information (hereafter, “EMM”) and are stored in an integrated circuit (IC) card, which is inserted into each receiving device. The scrambled ECM TP is first descrambled with the work key on the IC card, and the descrambling key is extracted from the descrambled ECM TP. After this, the program attribute information in the ECM and the subscription information, which is given to each user on an IC card, are compared to specify a program that can be descrambled. The specified program is then descrambled using the extracted descrambling key, and images and sounds for the program are presented to the user.  
      Such fee-based broadcast service usually allows users to watch a fee-based program at no charge for a predetermined time (hereafter a “preview time”).  
      Digitalization of a broadcast makes it possible to broadcast a great amount of digital data information other than video and audio data. Such digital data information broadcast is now available in a digital satellite broadcast service. In this digital satellite broadcast service, digital data information is broadcasted with video data and the like in only one direction from a sending station, and therefore there is no interactive process with receiving terminals in this transmission.  
      Japanese Laid-Open Patent Application No. 10-313449 discloses one example of such broadcasting. According to this patent application, a sending station repeatedly broadcasts a plurality of sets of digital data information, and a receiving terminal receives one of the plurality of sets of digital data information while switching from one set of data information to another to simulate interactive communication with the sending station. In this specification, digital data information broadcasted in this manner is called “interactive data”.  
      Broadcasting such interactive data, however, involves the following problems.  
      First, as there is no restrictions in viewing such interactive data during the aforementioned preview time, a viewer can view all the interactive data broadcasted with a previewed program, using a receiving terminal or the like during the preview time if the interactive data is not updated during a broadcast of the previewed program.  
      Secondly, interactive data is accumulated in memory of a receiving terminal, unlike video data and audio data. This allows a user freely to present interactive data, using the accumulated interactive data even after the preview time has expired. This is not desirable for a broadcast provider.  
     SUMMARY OF THE INVENTION  
      In view of the above problems, the present invention aims to provide a digital broadcast receiving device, a digital broadcast system, and a recording medium storing a receiving method and a receiving program, all of which can restrict use of interactive data relating to a fee-based program during a preview time.  
      The above object can be achieved by a digital broadcast receiving device that receives a broadcast wave including interactive data to achieve pseudo-interactive communications, the interactive data being repeatedly broadcasted, the digital broadcast receiving device including: a receiving unit for receiving the broadcast wave; a judging unit for judging a state that is established during the reception of the broadcast wave based on first information, the state being one of a preview state, a prohibited state, and a permitted state, wherein the first information shows conditions for using the received broadcast wave under a subscription contract, wherein in the preview state, the received broadcast wave is permitted to be used regardless of the subscription contract being made, and wherein in the prohibited state, the broadcast wave is prohibited from being used because the subscription contract is not made; and a restricting unit for restricting use of the interactive data when either the preview state or the prohibited state is judged as being established.  
      For this construction, use of interactive data can be restricted if either the preview state or the prohibited state is judged as being established. This can prevent users who have not paid a subscription fee from viewing all the interactive data.  
      Here, the interactive data may contain a plurality of sets of presentation data and link information which associates each of the plurality of sets of presentation data with a link to a set of presentation data. One of the plurality of sets of presentation data may be currently presented. The restricting unit may include: a user input receiving unit for receiving a user operation relating to the presented set of presentation data; a link unit for (a) specifying, based on the received user operation, a set of presentation data that is a link destination of a link associated by the link information with the presented set of presentation data if either the preview state or the prohibited state is judged as being established, (b) judging whether the specified set of presentation data and the presented set of presentation data are included in a same group, (c) obtaining the specified set of presentation data on judging that the specified set of presentation data and the presented set of presentation data are included in the same group, and (d) restricting use of interactive data relating to the received user operation on judging that the specified set of presentation data and the presented set of presentation data are not included in the same group; and a presenting unit for presenting the obtained set of presentation data.  
      For this construction, a set of presentation data that is a link destination of a link associated by the link information is obtained if this set of presentation is judged as being included in the same group as a currently-presented set of presentation data. When the two sets of presentation data are judged not to be included in the same group, a link operation designated by the received user operation is restricted. This can therefore provide a service that permits users who have not paid a subscription fee to view interactive data while at the same time restrict the use of interactive data.  
      Here, the interactive data may contain (a) a plurality of sets of presentation data, (b) link information which associates each of the plurality of sets of presentation data with a link to a set of presentation data, and (c) a script that contains a procedure to restrict use of the interactive data. The restricting unit may restrict the use of the interactive data by analyzing and executing the script.  
      With this construction, a script contained in a broadcast wave restricts use of interactive data. This allows a broadcast station to control restriction of interactive data use.  
      Here, the interactive data may contain (a) a plurality of sets of presentation data, (b) link information which associates each of the plurality of sets of presentation data with a link to a set of presentation data, and (c) a viewing enabled signal indicating either a viewing permission or a preview permission. One of the plurality of sets of presentation data may be currently presented. The restricting unit may include: a user operation receiving unit for receiving a user operation that designates a link operation; a link unit for obtaining a set of presentation data which is a link destination of the designated link operation if either a first condition or a second condition is fulfilled, and for restricting use of interactive data relating to the received user operation if neither the first condition nor the second condition is fulfilled, wherein in the first condition, the viewing enabled signal indicates the preview permission, and the preview state is judged as being established, and wherein in the second condition, the viewing enabled signal indicates the viewing permission, and the permitted state is judged as being established; and a presenting unit for presenting the obtained set of presentation data.  
      For this construction, a viewing enabled signal contained in a broadcast wave restricts use of interactive data, which allows a broadcast station to control restriction of interactive data use.  
      Here, the interactive data may contain (a) a plurality of sets of presentation data, and (b) link information which associates each of the plurality of sets of presentation data with a link to a set of presentation data. One of the plurality of sets of presentation data may be currently presented. The restricting unit may include: a user operation receiving unit for receiving a user operation; a counting unit for counting a number of user operations that have been received; a link unit for restricting use of interactive data relating to the received user operation when the counted number reaches a predetermine number and either the preview state or the prohibited state is judged as being established.  
      For this construction, the use of interactive data can be restricted in accordance with a number of user operations. This can provide a service that permits users to view interactive data based on the number of user operations while giving the restriction.  
      Here, the interactive data may contain (a) a plurality of sets of presentation data, and (b) link information which associates each of the plurality of sets of presentation data with a link to a set of presentation data. One of the plurality of sets of presentation data may be currently presented. The restricting unit may include: a user operation receiving unit for receiving a user operation that designates a link operation; a link unit for restricting use of interactive data relating to the received user operation if either the preview state or the prohibited state is judged as being established, and for obtaining a set of presentation data which is a link destination of the designated link operation if the permitted state is judged as being established; and a presenting unit for presenting the obtained set of presentation data.  
      With this construction, the use of interactive data relating to the received user operation is restricted if the preview state or the prohibited state is judged as being established. On the other hand, if the permitted state is judged as being established, a set of presentation data that is a link destination of the designated link operation is obtained to be presented. This prevents users who have not paid a subscription fee from viewing all the interactive data. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      These and the other objects, advantages and features of the invention will become apparent from the following description thereof taken in conjunction with the accompanying drawings which illustrate a specific embodiment of the invention.  
      In the drawings:  
       FIG. 1  is a block diagram showing a construction of a digital broadcast system  10  of an embodiment according to the present invention;  
       FIG. 2  shows a data construction of MPEG2 (Moving Picture Expert Group) transport stream  200 ;  
       FIG. 3  shows a data construction of a presentation element;  
       FIG. 4  is a block diagram showing a construction of an interactive data receiving device  100 ;  
       FIG. 5  shows information stored in the interactive data receiving device  100 ;  
       FIG. 6  is a flowchart showing the overall processing of the interactive data receiving device  100 ;  
       FIG. 7  is a flowchart showing the processing of a receiving unit;  
       FIG. 8  is a flowchart showing the processing of a specifying unit;  
       FIG. 9  is a flowchart showing the processing of a restoring unit;  
       FIG. 10  is a flowchart showing the processing of a data presentation restricting unit;  
       FIG. 11  is a flowchart showing the processing of a data analyzing unit;  
       FIG. 12  is a flowchart showing the processing of a data judging unit;  
       FIG. 13  is a flowchart showing ID (Identification) judgement by the data judging unit;  
       FIG. 14  is a flowchart showing the processing of a data operation restricting unit;  
       FIG. 15  is a flowchart showing modification ID judgement by the data judging unit;  
       FIG. 16  is a flowchart showing another modification ID judgement by the data judging unit;  
       FIG. 17  shows an example script received by the interactive data receiving device  100 ;  
       FIG. 18  is a flowchart showing modification processing of the data analyzing unit;  
       FIG. 19  is a flowchart showing the processing to analyze and execute a script;  
       FIG. 20  is a flowchart showing example processing by the data analyzing unit to execute a script;  
       FIG. 21  shows an example script received by the interactive data receiving device  100 ;  
       FIG. 22  is a flowchart showing another processing by the data analyzing unit;  
       FIG. 23  is a flowchart showing another processing by the data analyzing unit;  
       FIG. 24  shows an example presentation element received by the interactive data receiving device  100 ;  
       FIG. 25  is a flowchart showing another processing by the data presentation restricting unit;  
       FIG. 26  is a flowchart showing another processing by the data operation restricting unit;  
       FIG. 27  is a flowchart showing another processing by the data operation restricting unit;  
       FIG. 28  is a flowchart showing another processing by the data presentation restricting unit; and  
       FIG. 29  is a flowchart showing another processing by the data operation restricting unit. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The following describes a digital broadcast system  10  of the present invention, using several embodiments.  
      1. Construction of Digital Broadcast System  10   
      As shown in  FIG. 1 , the digital broadcast system  10  comprises a sending device  20 , a broadcast satellite  30 , a plurality of interactive data receiving devices  100   a,    100   b  . . . , and a plurality of monitors.  
      1.1 Sending Device  20   
      The sending device  20  is installed in a broadcast station that provides a digital broadcast service, and sends an MPEG2 (Moving Picture Expert Group) TP (transport stream) as a broadcast wave via the broadcast satellite  30 . This MPEG2 TS contains a reception signal and viewing permission information that is used to restrict a viewing of a fee-based program and charge a fee-based program. The reception signal is composed of video data, audio data, interactive data, and the like.  
       FIG. 2  shows a data construction of an MPEG2 TS used to transmit interactive data.  
      When transmitted, the MPEG2 TS  200  is divided into packets on a transmission channel. Each packet contains a different packet ID (PID), which is identification information for the packet. A plurality of packets that has the same PID to be transmitted make up the same component.  
      As shown in  FIG. 2 , the MPEG2 TS  200  includes components  217 ,  219 ,  201 ,  204 , and other components that are not shown in the figure. Each component contains a different component ID that identifies the component. The components  201  and  204  contains component IDs “400” and “500”, respectively. Component IDs of the components  217  and  219  are not shown in the figure.  
      The component  217  includes viewing permission information  218 , which contains subscription information given for each program. The subscription information contains, for instance, information showing that a program is allowed to be viewed periodically, and information showing that a program is charged on an as-used basis as in Pay Per View. Video data and audio data are included in a video data component and an audio data component, which are not shown in the figure.  
      The component  219  includes viewing permission information  220 , which contains a user ID that identifies a user who subscribes to a program.  
      The component  201  includes reception elements  202 ,  214 , and other reception elements. The reception element  202  contains a presentation element  203  and other presentation elements.  
      Each reception element has a different reception element ID to identify the reception element, and each presentation element has a different presentation ID to identify the presentation element.  
      More specifically, the reception elements  202  and  214  are identified by reception element IDs “410” and “420”, as shown in  FIG. 2 . The presentation element  203  is identified by a presentation element ID “411”.  
      The component  204  includes reception elements  205 ,  207 , and other reception elements. The reception element  205  includes presentation elements  206  and  213 , and other presentation elements. The reception element  207  contains presentation elements  208  and  209 , and other presentation elements.  
      In the MPEG2 transport stream  200 , the components  201  and  204  are interactive data, and reception elements included in these components  201  and  204  are repeatedly transmitted.  
      With this interactive data, one presentation element is switched to another when links defined in the interactive data are followed. A presentation element includes text data, bitmapped data, hyperlink data, and a script describing a procedure, as shown in  FIG. 17 .  
       FIG. 3  shows a data construction of the presentation element  206  as one example.  
      As shown in the figure, the presentation element  206  includes a bitmap table, a text table, a script table, and a hyperlink table.  
      The bitmap table stores a pair composed of a set of bitmap data to be displayed and a bitmap index which identifies this set of bitmap data. Specifically, the bitmap table associates indexes “0”, “1”, and “2” with sets of bitmap data “TOKYO”, “OSAKA”, and “TO NEWS”, respectively.  
      The text table stores a pair composed of a set of text data and a text index identifying this set of text data. Specifically, the text table associates a text index “0” with a set of text data “WEATHER FORECAST”.  
      The script table stores a pair composed of a script describing a procedure, and a script index identifying this script. Specifically, the script table associates a script index “0” with a script.  
      The hyperlink table associates a link index, which identifies a link, with a destination of this link. Specifically, the hyperlink table associates link indexes “210”, “211”, and “212” with “ID=512”, “ID=511”, and “ID=521” that each identify a link destination.  
      Note that two pairs written in the same row in the bitmap table and the hyperlink table are associated with one another.  
      More specifically, with the presentation element  206 , bitmap data “OSAKA” is linked via a link of the link index “210” (hereafter, this link is referred to as “a link ‘210’”) to the presentation element  208 . Bitmap data “TOKYO” is linked via a link of the link index “211” (hereafter, a link “211”) to the presentation element  209 .  
      Similarly, the presentation element  208  is linked via the link  210  to the presentation element  206 , and the presentation element  209  is linked via the link  211  to the presentation element  206 .  
      1.2 Construction of Interactive Data Receiving Device  100   
      The interactive data receiving devices  100   a,    100   b  . . . have the same construction. The following therefore uses an interactive data receiving device  100  to describe the construction common to all the interactive data receiving devices  100   a,    110   b  . . . .  
      As shown in  FIG. 4 , the interactive data receiving device  100  includes a receiving unit  101 , a specifying unit  102 , a restoring unit  103 , a data analyzing unit  104 , an AV reproducing unit  105 , a combining unit  106 , a control unit  107 , a data storing unit  108 , an IC card input/output unit  109 , an inputting unit  110 , a data presentation restricting unit  115 , a data operation restricting unit  116 , and a data judging unit  117 .  
      (1) Data Storing Unit  108   
      The data storing unit  108  is composed of semiconductor memory, and has areas that store a presentation element, a purchase state, a component ID, a reception element ID, and a presenting element flag, as shown in  FIG. 5 .  
      The presentation element was described above, and so will not be described.  
      The purchase state shows a state of a program presented to a user. The purchase state is shown as a value representing one of the following states: a viewing permitted state; a preview state; and a viewing prohibited state. The viewing permitted state is a state in which the user has purchased the program and is permitted to view the program. The preview state is a state in which the user, who has not purchased the program, is permitted to view the program for a predetermined time (hereafter, “a preview time”). The preview time may be one minute, for instance. The viewing prohibited state is a state in which the above preview time has expired and the user who has not purchased the program is prohibited from viewing.  
      The presenting element flag indicates whether the stored presentation element is now presented by the monitor. When the presenting element flag is shown as “1”, the stored presentation element is presented by the monitor. When the presenting element flag is shown as “0”, the presentation element is not presented.  
      (2) IC Card Input/Output Unit  109   
      The IC card input/output unit  109  performs a read from an IC card.  
      This IC card is composed of semiconductor memory, and stores subscription information for the user. The IC card is inserted into the interactive data receiving device  100  by the user, and connected to the IC card input/output unit  109 .  
      The IC card input/output unit  109  reads the subscription information from the IC card, and outputs the read subscription information to the specifying unit  102  via the control unit  107 .  
      (3) Receiving Unit  101   
      The receiving unit  101  receives an MPEG2 TS (hereafter, “TS”), which is transmitted repeatedly from the sending device  20  as a broadcast wave, and extracts a reception signal and viewing permission information from the received TS. This reception signal contains video data, audio data, and interactive data. The receiving unit  101  then outputs the extracted reception signal to the restoring unit  103 , and the extracted viewing permission information to the specifying unit  102 .  
      (4) Specifying Unit  102   
      The specifying unit  102  receives the viewing permission information from the receiving unit  101 , and specifies a purchase state, using the received viewing permission information as follows.  
      The specifying unit  102  receives the subscription information stored on the IC card from the IC card input/output unit  109  via the control unit  107 , and compares this subscription information with subscription information in the received viewing permission information. When the two is the same, the specifying unit  102  judges that the user has purchased a fee-based program under contract and specifies the viewing permitted state as the purchase state. When the two is not the same, the specifying unit  102  judges that the user has not purchased the fee-based program, and further judges whether the present time is in the preview time. If so, the specifying unit  102  specifies the preview state as the purchase state. If not, i.e., the present time has passed the preview time, the specifying unit  102  specifies the viewing prohibited state as the purchase state.  
      The specifying unit  102  then generates a purchase state signal that is a value showing the specified purchase state, and outputs the generated purchase state signal to the restoring unit  103 .  
      Note that the specifying unit  102  may alternatively output this purchase state signal directly to the data analyzing unit  104 , the data presentation restricting unit  115 , and the data operation restricting unit  116 .  
      (5) Restoring Unit  103   
      On receiving the reception signal from the receiving unit  101 , the restoring unit  103  separates this reception signal to generate the video data, the audio data, and the interactive data. The restoring unit  103  outputs the generated audio data and video data to the AV reproducing unit  105  as a first AV signal, and outputs the generated interactive data to the data presentation restricting unit  115  as a first data signal. The restoring unit  103  also receives the purchase state signal from the specifying unit  102 , stores this state signal, and outputs a signal that is the same as the state signal to the data presentation restricting unit  115 .  
      (6) AV Reproducing Unit  105   
      The AV reproducing unit  105  receives the first AV signal from the restoring unit  103 , reproduces this first AV signal to generate a second AV signal, and outputs the generated second AV signal to the combining unit  105 .  
      (7) Combining Unit  106  and Monitor  
      The combing unit  106  receives the second AV signal from the AV reproducing unit  105 , and a second data signal from the data analyzing unit  104 . The combining unit  106  then combines the second AV signal and the second data signal to generate a data-AV combined signal, and outputs the generated data-AV combined signal to the monitor connected to the interactive data receiving device  100 .  
      The monitor then receives this data-AV combined signal, and outputs the received data-AV combined signal.  
      (8) Data Presentation Restricting Unit  115   
      On receiving the first data signal and the purchase state signal from the restoring unit  103 , the data presentation restricting unit  115  outputs them to the data analyzing unit  104 .  
      (9) Inputting Unit  110   
      The inputting unit  110  is composed of a remote controller or the like. This remote controller has buttons on its surface, such as a power ON/OFF button, numeric buttons, an “UP” button, a “DOWN” button, a “RIGHT” button, a “LEFT” button, a select button, a selection confirmation button. When the user pushes one of these buttons, the inputting unit  110  generates an interactive data operation signal containing button information corresponding to the pushed button, and outputs the interactive data operation signal to the control unit  107 .  
      (10) Control Unit  107   
      On receiving the interactive data operation signal from the inputting unit  110 , the control unit  107  outputs it to the data operation restricting unit  116 .  
      (11) Data Analyzing Unit  104   
      The data analyzing unit  104  receives the first data signal and the purchase state signal from the data presentation restricting unit  115 , and receives the interactive data operation signal from the data operation restricting unit  116 .  
      The data analyzing unit  104  then analyzes one of presentation elements included in the first data signal, and generates video data for the analyzed presentation element presented to the user. The data analyzing unit  104  then outputs the generated video data as the second data signal to the combing unit  106 . In more detail, the presentation elements in the above first data signal includes a presentation element that contains information showing that this presentation element should be first presented. The data analyzing unit  104  first specifies this presentation element, and then generates and outputs the second data signal for the specified presentation element.  
      When receiving the interactive data operation signal from the control unit  107 , the data analyzing unit  104  selects one of the plurality of presentation elements included in the above first data signal in accordance with the received interactive data operation signal. The data analyzing unit  104  then generates a second data signal for the selected presentation element as described above, and outputs the generated second data signal.  
      More specifically, when video data for the presentation element  206  is displayed by the monitor and the user selects “TOKYO”, for instance, the control unit  107  receives the interactive data operation signal indicating that “TOKYO” is selected, which is outputted to the data analyzing unit  104 . The data analyzing unit  104  then selects the presentation element  209  which is a link destination of “TOKYO”, extracts the selected presentation element  209  from the first data signal, and generates video data from the extracted presentation element  209 . After this, the data analyzing unit  104  outputs the generated video data as the second data signal via the combining unit  106  to the monitor, which then displays this video data.  
      The data analyzing unit  104  also outputs the received purchase state -signal and first data signal to the data operation restricting unit  116  and the data judging unit  117 , respectively.  
      (12) Data Judging Unit  117   
      The data judging unit  117  receives the first data signal from the data analyzing unit  104 , and interactive data operation information from the data operation restricting unit  116 .  
      The data judging unit  117  then specifies, out of a bitmap table contained in a currently-presented presentation element included in the received first data signal, a pair composed of: (a) bitmap data specified by the received interactive data operation information; and (b) a bitmap index.  
      After this, the data judging unit  117  specifies, out of a hyperlink table in the above presentation element, a pair which is associated with the pair specified above and composed of a link index and a link destination, and recognizes the link destination.  
      The data judging unit  117  then compares the ID of the recognized link destination with the ID of the currently-presented presentation element to judge whether a presentation element of the link destination and the currently-presented presentation element belong to the same component. In more detail, the data judging unit  117  judges whether the highest-order digit of the link destination ID and that of the currently-presented presentation element ID are the same. If so, the data judging unit  117  generates a judgement result showing that the two is the same (hereafter, this judgement result is referred to as “same”). If not, the data judging unit  117  generates a judgement result showing that the two is not the same (hereafter, this judgement result is referred to as “different”).  
      Note that this judging method is only one example, and other judging methods may be alternatively used.  
      The data judging unit  117  then outputs the generated judgement result to the data operation restricting unit  116 .  
      Each presentation element ID consists of three decimal digits. When IDs of different presentation elements have the same highest-order digit, these presentation elements are included in the same component. When IDs of different presentation elements have the same second-order digit, as well as the same highest-order digit, these presentation elements are included in the same reception element in the same component.  
      (13) Data Operation Restricting Unit  116   
      The data operation restricting unit  116  receives the interactive data operation signal from the control unit  107 , the judgement result from the data judging unit  117 , and the purchase state signal from the data analyzing unit  104 .  
      The data operation restricting unit  116  outputs the received interactive data operation signal to the data judging unit  117  as the interactive data operation information.  
      When the received purchase state signal indicates the viewing permitted state, the data operation restricting unit  116  outputs the received interactive data operation signal to the data analyzing unit  104 . The data operation restricting unit  116  also outputs the interactive data operation signal to the data analyzing unit  104  when the received purchase state signal indicates either the preview state or the viewing prohibited state and the received judgement result is shown as “same”.  
      1.3 Processing of Interactive Data Receiving Device  100   
      The following describes the processing of the interactive data receiving device  100 .  
      (1) Overall Processing  
      The following describes the overall processing of the interactive data receiving device  100  with reference to a flowchart of  FIG. 6 .  
      The IC card input/output unit  109  reads subscription information for a user from an IC card (step S 101 ).  
      The receiving unit  101  receives a TS (step S 102 ), and the specifying unit  102  generates and outputs a purchase state signal (step S 103 ).  
      When both steps S 102  and S 103  have been completed, the restoring unit  103  generates a first data signal (step S 104 ).  
      After step S 101 , on the other hand, the inputting unit  110  receives a user operation (step S 111 ), and the control unit  107  outputs an interactive data operation signal (step S 112 ).  
      After step S 104 , the data presentation restricting unit  115  performs operations (step S 105 ), and the data analyzing unit  104  performs operations (step S 106 ). The data judging unit  117  then performs operations (step S 107 ), and the data operation restricting unit  116  performs operations (step S 108 ). The control flow then returns to step S 106 .  
      After step S 104 , the AV reproducing unit  105  generates a second AV signal (step S 109 ). When both steps S 109  and S 106  have been completed, the combining unit  106  generates a data-AV combined signal, and outputs it to the monitor (step S 110 ). After this, the control flow returns to step S 102  so that the operations are repeated.  
      (2) Processing of Receiving Unit  101   
      The following describes the processing of the receiving unit  101  with reference to a flowchart of  FIG. 7 .  
      The receiving unit  101  receives a TS (step S 121 ), and extracts a reception signal and viewing permission information from the received TS (step S 122 ). The receiving unit  101  then outputs the extracted reception signal to the restoring unit  103  (step S 123 ), and outputs the extracted viewing permission information to the specifying unit  102  (step S 124 ). The control flow then moves to step S 121 , and the above processing is repeated.  
      (3) Specifying Unit  102   
      The following describes the processing of the specifying unit  102  with reference to a flowchart of  FIG. 8 .  
      The specifying unit  102  receives the viewing permission information from the receiving unit  101  (step S 141 ), and obtains subscription information for the user from the IC card input/output unit  109  via the control unit  107  (step S 142 ). The specifying unit  102  then compares this obtained subscription information with subscription information in the received viewing permission information. If the two is the same (step S 143 ), the specifying unit  102  generates a purchase state signal indicating the viewing permitted state (step S 147 ). If the two is not the same (step S 143 ), the specifying unit  102  judges whether the present time is a preview time (step S 144 ). If so, the specifying unit  102  generates a purchase state signal indicating the preview state (step S 146 ). If not, the specifying unit  102  generates a purchase state signal indicating the viewing prohibited state (step S 145 ).  
      After this, the specifying unit  102  outputs the generated purchase state signal to the restoring unit  103  (step S 148 ).  
      (4) Processing of Restoring Unit  103   
      The following describes the processing of the restoring unit  103  with reference to a flowchart of  FIG. 9 .  
      The restoring unit  103  receives the reception signal from the receiving unit  101  (step S 161 ), and separates the received reception signal to generate video data, audio data, and interactive data (step S 162 ). The restoring unit  103  then outputs the generated audio data and video data to the AV reproducing unit  105  as a first AV signal (step S 163 ), and outputs the generated interactive data to the data presentation restricting unit  115  as a first data signal (step S 164 ). The control flow them moves to either step S 161  or step S 165 , and the processing is repeated.  
      The restoring unit  103  also receives the purchase state signal from the specifying unit  102  (step S 165 ), stores this state signal (step S 166 ), and outputs the same signal as this purchase state signal to the data presentation restricting unit  115  (step S 167 ). The control flow then returns to either step S 161  or step S 165 , and the processing is repeated.  
      (5) Processing of Data Presentation Restricting Unit  115   
      The following describes the processing of the data presentation restricting unit  115  with reference to the flowchart of  FIG. 10 .  
      The data presentation restricting unit  115  receives the first data signal and the purchase state signal from the restoring unit  103  (step S 181 ), and outputs them to the data analyzing unit  104  (step S 182 ).  
      (6) Processing of Data Analyzing Unit  104   
      The following describes the processing of the data analyzing unit  104  with reference to a flowchart of  FIG. 11 .  
      The data analyzing unit  104  receives the first data signal and the purchase state signal from the data presentation restricting unit  115  (step S 201 ), and receives an interactive data operation signal from the data operation restricting unit  116  (step S 202 ).  
      When the received first data signal does not include any presentation element containing information showing that the presentation element should be first presented (step S 203 ) and the data analyzing unit  104  has received the interactive data operation signal (step S 206 ), the data analyzing unit  104  selects a presentation element indicated by the received interactive data operation signal from the received first data signal (step S 207 ).  
      The data analyzing unit  104  then generates video data, referring to tables, such as a bitmap table and a text table, contained in the selected (or firstly-presented) presentation element (step S 204 ), and outputs the generated video data as a second data signal to the combining unit  106  (step S 205 ).  
      The data analyzing unit  104  also outputs the received purchase state signal to the data operation restricting unit  116  (step S 208 ).  
      After this, the control flow returns to step S 201 , and the processing is repeated.  
      (7) Processing of Data Judging Unit  117   
      The following describes the processing of the data judging unit  117  with reference to flowcharts of  FIGS. 12 and 13 .  
      The data judging unit  117  receives the first data signal from the data analyzing unit  104  (step S 221 ), and receives the interactive data operation information from the data operation restricting unit  116  (step S 222 ).  
      The data judging unit  117  then specifies, out of a bitmap table contained in a currently-presented presentation element included in the received first data signal, a pair composed of: (a) bitmap data specified by the received interactive data operation information; and (b) a bitmap index (step S 223 ).  
      After this, the data judging unit  117  specifies, out of a hyperlink table contained in the above presentation element, a pair which is associated with the pair specified above and composed of a link index and a link destination, and recognizes the link destination (step S 244 ).  
      The data judging unit  117  then compares the ID of the recognized link destination with the currently-presented presentation element ID to judge whether a presentation element of the link destination and the currently-presented presentation element belong to the same component (step S 255 ).  
      The data judging unit  117  then outputs the judgement result to the data operation restricting unit  116  (step S 226 ).  
      The following describes the detailed processing in step S 255  with reference to a flowchart of  FIG. 13 .  
      The data judging unit  117  judges whether the highest-order digit of the link destination ID and that of the currently-presented presentation element ID are the same (step S 241 ). If so, the data judging unit  117  generates a judgement result shown as “same”. If not, the data judging unit  117  generates a judgement result shown as “different” (step S 245 ).  
      (8) Processing of Data Operation Restricting Unit  116   
      The following describes the processing of the data operation restricting unit  116  with reference to a flowchart of  FIG. 14 .  
      The data operation restricting unit  116  receives the interactive data operation signal from the control unit  107  (step S 261 ), and outputs the received interactive data operation signal to the data judging unit  117  as the interactive data operation information (step S 262 ).  
      The data operation restricting unit  116  receives the purchase state signal from the data analyzing unit  104  (step S 263 ), and receives the judgement result from the data judging unit  117  (step S 264 ). When the received purchase state signal indicates the viewing permitted state (step S 265 ), the data operation restricting unit  116  outputs the received interactive data operation signal to the data analyzing unit  104  (step S 267 ). After this, the control flow returns to either step S 261  or step S 263 .  
      On the other hand, when the received purchase state signal indicates either the preview state or the viewing prohibited state (step S 265 ) and the received judgement result is shown as “same” (step S 266 ), the data operation restricting unit  116  outputs the interactive data operation signal to the data analyzing unit  104  (step S 267 ). After this, the control flow returns to either step S 261  or step S 263 .  
      When the judgement result is shown as “different” (step S 266 ), the control flow returns to either step S 261  or step S 263 .  
      1.3 Considerations  
      As has been described, the data judging unit  117  refers to a first data signal and interactive data operation information, compares a component that includes currently-presented interactive data with a component that includes interactive data corresponding to a hyperlink destination, and generates a judgement result. The data judging unit  117  then outputs the generated judgment result to the data operation restricting unit  116 . When the judgement result shows that the above two components are not the same, the data operation restricting unit  116  does not output the received interactive data operation signal to prohibit a link to the above hyperlink destination.  
      The link to this hyperlink destination is performed unless the purchase state signal indicates the viewing prohibited state or the preview state, i.e., if the purchase state signal indicates the viewing permitted state. When the purchase state signal indicates the viewing prohibited state or the preview state, the data judging unit  117  makes the above judgement, and the link to the hyperlink destination is performed if the two components are the same. If the two components are different, this link is ignored.  
      For instance, if currently-presented interactive data is the presentation element  213  in  FIG. 2  and the user clicks on “TO WEATHER FORECAST”, a link to the presentation element  206 , which is included in the same component as that including hyperlink data “TO WETHER FORECAST”, is performed. A link to the presentation element  215  in a different component, however, is ignored.  
      In this way, the interactive data receiving device  100  restricts a link destination within a component that includes interactive data presented first.  
      2. Example Modifications  
      The present invention has been described using the above embodiment. It should be clear, however, that the present invention is not limited to the above embodiment. The following describes example modifications, mainly modifications to data analysis, data presentation, and user-operation restrictions performed by the data analyzing unit  104 , the data presentation restricting unit  115 , and the data operation restricting unit  116 .  
      (1) Restricting Link Destination to Firstly-Presented Reception Element  
      The following describes an example modification to step S 225  in  FIG. 12  with reference to a flowchart of  FIG. 15 .  
      The data judging unit  117  judges whether the highest-order digit of the link destination presentation element ID and that of the currently-presented presentation element ID are the same (step S 241 ) and, if so, further judges if the second-order digit of the link destination ID and that of the currently-presented presentation element ID are the same (step S 242 ). If so, the data judging unit  117  generates a judgement result shown as “same” (step S 244 ). If not, the data judging unit  117  generates a judgement result shown as “different” (step S 245 ).  
      In this way, the data judging unit  117  refers to the first data signal and the interactive data operation information, and compares a reception element including currently-presented interactive data with a reception element including interactive data that is a link destination of hyperlink data. The data judging unit  117  then generates and outputs a judgement result to the data operation restricting unit  116 . When the judgement result is shown as “different”, the data operation restricting unit  116  does not output the received interactive data operation signal so that a link designated by the interactive data operation signal is prohibited.  
      For instance, when the presentation element  206  shown in  FIG. 2  is now presented and a user clicks on “TO NEWS”, the link  212  to the presentation element  213  is performed. On the other hand, if the user clicks on “TOKYO” or “OSAKA”, the link  210  to the presentation element  208 , or the link  211  to the presentation element  209 , respectively, is ignored.  
      (2) Restricting Link Destination to Firstly-Presented Presentation Element  
      The following describes another example modification to step S 225  in  FIG. 12  with reference to a flowchart of  FIG. 16 .  
      The data judging unit  117  judges whether the highest-order digit of the link destination presentation element ID and that of the currently-presented presentation element ID are the same (step S 241 ). If so, the data judging unit  117  further judges if the second-order digit of the link destination ID and that of the currently-presented presentation element ID are the same (step S 242 ). If so, the data judging unit  117  further judges whether the lowest-order digits of the two IDs are the same (step S 243 ). If so, the data judging unit  117  generates a judgement result shown as “same” (step S 244 ). When giving the “no” judgement in step S 241  or step S 242 , the data judging unit  117  generates a judgement result shown as “different” (step S 245 ).  
      In this way, the data judging unit  117  refers to the first data signal and the interactive data operation information, and compares a presentation element including currently-presented interactive data with a presentation element including interactive data that is a link destination of hyperlink data. The data judging unit  117  then generates and outputs a judgement result to the data operation restricting unit  116 . When the judgement result indicates that the two presentation elements are different, the data operation restricting unit  116  does not output a received interactive data operation signal so that a link designated by the interactive data operation signal is prohibited.  
      For instance, when the presentation element  206  is now presented and a user clicks on “OSAKA”, “TOKYO”, or “TO NEWS”, the link  210  to the presentation element  208 , the link  211  to the presentation element  209 , or the link  212  to the presentation element  213 , respectively, is ignored.  
      (3) Restriction Placed by Script on Presentation and Operation of Interactive Data {circle around (1)} 
      The sending device  20  transmits a TS including a presentation element that contains a script as shown in  FIG. 17 . The receiving unit  101  in the interactive data receiving device  100  receives this TS, and the restoring unit  103  outputs a first data signal that is interactive data including the above presentation element that contains the script to the data presentation restricting unit  115 , which then outputs this first data signal to the data analyzing unit  104 .  
      The script shown in  FIG. 17  contains a value shown as “PRESENTATION ELEMENT 1” on the second line. This value is variable, like an argument of a function. For instance, if this script is included in the presentation element  208 , this value “PRESENTATION ELEMENT 1” is replaced by a value indicating a presentation element ID of the presentation element  206 . If this script is included in the presentation element  206 , this value is replaced by a value indicating a presentation element ID of the presentation element  213 .  
      The following describes the processing of the data analyzing unit  104  with reference to a flowchart of  FIG. 18 .  
      With this flowchart, in a step having the same reference number as a step in  FIG. 11 , the same operation as shown in the step in  FIG. 11  is performed. The following description focuses on operations unique to the flowchart of  FIG. 18 .  
      After step S 201  or step S 202 , the data analyzing unit  104  judges if a presentation element that should be firstly presented or that is specified by the received interactive data operation signal includes a script (step S 211 ). If so, the data analyzing unit  104  executes this script (step S 212 ), and the control flow returns to step S 201 , so that the processing is repeated.  
      The following describes the processing of step S 212  in detail with reference to a flowchart of  FIG. 19 .  
      The data analyzing unit  104  judges whether all the lines in a script have been read (step S 281 ). If not, the data analyzing unit  104  reads a line from the script (step S 282 ), analyzes the read line (step S 283 ), and performs operations in accordance with an analysis result (step S 284 ). When all the lines have been read (step S 281 ), the processing is terminated.  
      When executing the script shown in  FIG. 17 , the data analyzing unit  104  operates as shown in a flowchart of  FIG. 20 .  
      When the purchase state signal indicates the viewing permitted state (step S 301 ) and the interactive data operation signal has been received (step S 302 ), the data analyzing unit  104  selects a presentation element in accordance with the received interactive data operation signal (step S 303 ). Following this, the data analyzing unit  104  generates video data, which is a second data signal, referring to a bitmap table, a text table, and the like included in the selected presentation element (step S 304 ), and outputs the generated second data signal to the combining unit  106  (step S 305 ). The processing is then completed.  
      When the purchase state signal indicates the preview state (step S 301 ), the data analyzing unit  104  generates video data, which is a second data signal, referring to a bitmap table, a text table, and the like included in a firstly-presented presentation element (step S 304 ), and outputs the generated second data signal to the combining unit  106  (step S 305 ). The processing is then completed.  
      When the purchase state signal indicates the viewing prohibited state (step S 301 ), the data analyzing unit  104  shortly completes the processing.  
      (4) Restriction Placed by Script on Presentation and Operation of Interactive Data {circle around (2)} 
      In this modification example, the interactive data receiving device  100  has a script area for storing a script. This script area is composed of semiconductor memory, and is left blank to represent an initial value.  
      Note that this script area may alternatively store the script shown in  FIG. 17  as the initial value, or the interactive data receiving device  100  may receive an initial script as the initial value via a broadcast wave, and the script area may store this initial value.  
      The sending device  20  broadcasts a TS including a presentation element containing a script as shown in  FIG. 21 . The script shown in the figure contains: (a) an update instruction to have an instruction registered; and (b) the instruction to be registered. This update instruction may alternatively be an instruction to change, add, or delete an instruction. The receiving unit  101  in the interactive data receiving device  100  receives this TS, and the restoring unit  103  outputs a first data signal that is interactive data including the above presentation element that contains the above script to the data presentation restricting unit  115 , which then outputs this first data signal to the data analyzing unit  104 . The data analyzing unit  104  then analyzes the update instruction in the script, and if the update instruction indicates that an instruction should be registered, changed, added, or deleted, the data analyzing unit  104  registers, makes a change to the instruction, or adds the instruction to or deletes the instruction from the script area. After this, the data analyzing unit  104  executes the instruction included in the script.  
      The following specifically describes this processing. The data analyzing unit  104  performs the processing similar to that shown in the flowchart of  FIG. 18 . Operations unique to this example modification are described below with reference to a flowchart of  FIG. 22 .  
      The data analyzing unit  104  judges if a presentation element that should be firstly presented or that is specified by the received interactive data operation signal includes a script in step S 211  in  FIG. 18 , which is equal to step S 211  in  FIG. 22 . If so, the data analyzing unit  104  further judges if this script contains an update instruction (step S 401 ). If not, the data analyzing unit  104  executes the script (step S 212 ), and the control flow returns to step S 201 . When judging that the script contains an update instruction (step S 401 ) and that the contained update instruction is to register an instruction contained in the script (step S 402 ), the data analyzing unit  104  overwrites this instruction onto an instruction stored in the script area (step S 403 ) and executes the script (step S 407 ). The control flow then returns to step S 201 .  
      When judging that the update instruction is to make a change to an instruction (step S 402 ), the data analyzing unit  104  updates the instruction, which is stored in the script area (step S 404 ), and executes the script (step S 407 ). The control flow then returns to step S 201 .  
      When judging that the update instruction is to add an instruction (step S 402 ), the data analyzing unit  104  registers the instruction in the script into the script area (step S 405 ), and executes the script (step S 407 ). The control flow then returns to step S 201 .  
      When judging that the update instruction is to delete an instruction (step S 402 ), the data analyzing unit  104  deletes the instruction specified in the script from the script area (step S 404 ), and executes the script (step S 407 ). The control flow then returns to step S 201 .  
      For instance, when executing the script shown in  FIG. 21 , the data analyzing unit  104  performs, in step S 407  in  FIG. 22 , the processing shown in a flowchart of  FIG. 23 .  
      When judging that the purchase state signal indicates the viewing permitted state (step S 321 ) and when receiving the interactive data operation signal (step S 323 ), the data analyzing unit  104  selects a presentation element in accordance with the received interactive data operation signal (step S 324 ). The data analyzing unit  104  then generates video data, which is a first data signal, using a bitmap table, a text table, and the like (step S 325 ), outputs the generated first data signal to the combining unit  106  (step S 326 ), and completes the processing.  
      On the other hand, when judging that the purchase state signal is either the preview state or the viewing prohibited state (step S 321 ), the data analyzing unit  104  generates a second data signal containing a message indicating that no operations are performed unless the user purchases a program (step S 322 ), and outputs the generated second data signal to the combining unit  106  (step S 326 ). This completes the processing of the flowchart.  
      In this way, when a script contains an instruction to perform a link via hypertext data (hereafter, such instruction is called a “hyperlink instruction”), this link is performed only when the purchase state signal indicates the viewing permitted state. When the purchase state signal indicates the viewing prohibited state or the preview state, the link is not performed, and a message indicating a reason for the unperformed link is presented to the user instead.  
      (5) Restrictions Placed by Viewing Enabled Signal Assigned to Presentation Element or Reception Element on Interactive Data Presentation and Operation  
      In this example modification, the sending device  20  transmits a TS including a presentation element that contains a viewing enabled signal as shown in  FIG. 24 . The viewing enabled signal indicates either the preview state or the viewing permitted state.  
      The receiving unit  101  in the interactive data receiving device  100  receives the above TS, and the restoring unit  103  outputs, as a first data signal, interactive data including the above presentation element containing the above viewing enabled signal to the data presentation restricting unit  115 . The data presentation restricting unit  115  then outputs this first data signal to the data analyzing unit  104 . The data analyzing unit  104  then judges that the above presentation element contains the viewing enabled signal, extracts the viewing enabled signal from the presentation element, and outputs the extracted viewing enabled signal to the data operation restricting unit  116 .  
      Note that the above viewing enabled signal may be alternatively contained in a reception element, instead of a presentation element.  
      The following described the processing of the data presentation restricting unit  115  of the present modification with reference to a flowchart of  FIG. 25 .  
      The data presentation restricting unit  115  receives the first data signal and the purchase state signal from the restoring unit  103  (step S 181 ).  
      When the received purchase state signal indicates the viewing permitted state (step S 183 ) and the viewing enabled signal also indicates the viewing permitted state (step S 184 ), the data presentation restricting unit  115  outputs the received first data-signal and purchase state signal to the data analyzing unit  104  (step S 182 ), and the control flow returns to step S 181 . When the viewing enabled signal does not indicate the viewing permitted state (step S 184 ), the control flow returns to step S 181 .  
      On the other hand, when the received purchase state signal indicates the preview state (step S 183 ) and the viewing enabled signal also indicates the preview state (step S 185 ), the data presentation restricting unit  115  outputs the received first data signal and purchase state signal to the data analyzing unit  104  (step S 182 ), and the control flow returns to step S 181 . If the viewing enabled signal does not indicate the preview state (step S 185 ), the control flow returns to step S 181 .  
      When the purchase state signal indicates neither the preview state nor the viewing permitted state (step S 183 ), the control flow returns to step S 181 .  
      As is described above, a viewing enabled signal indicating either the preview state or the viewing permitted state is assigned to a presentation element or a reception element in advance. The data presentation restricting unit  115  then specifies interactive data in accordance with the purchase state signal and the viewing enabled signal, and permits presentation of the specified interactive data only.  
      After the above processing, the data operation restricting unit  116  operates as shown in a flowchart of  FIG. 26 .  
      The data operation restricting unit  116  receives either: the purchase state signal and the viewing enabled signal; or only the purchase state signal (step S 341 ). When judging that the viewing enabled signal has not been received (step S 342 ), the data operation restricting unit  116  performs the same processing as that shown in the flowchart of  FIG. 14  (step S 347 ). The control flow then returns to step S 341 .  
      On the other hand, when the data operation restricting unit  116  judges that the viewing enabled signal has been received (step S 342 ) and when the purchase state signal indicates the preview state (step S 343 ), the data operation restricting unit  116  further judges if the received viewing enabled signal also indicates the preview state (step S 345 ). If so, the data operation restricting unit  116  outputs the received interactive data operation signal to the data analyzing unit  104  (step S 346 ), and the control flow returns to step S 341 . When the viewing enabled signal does not indicate the preview state (step S 345 ), the control flow returns to step S 341 .  
      When the purchase state signal indicates the viewing permitted state (step S 343 ) and the viewing enabled signal also indicates the viewing permitted state (step S 344 ), the data operation restricting unit  116  outputs the interactive data operation signal to the data analyzing unit  104  (step S 346 ), and the control flow returns to step S 341 . When the viewing enabled signal does not indicate the viewing permitted state (step S 344 ), the control flow returns to step S 341 .  
      When the purchase state signal indicates neither the preview state nor the viewing permitted state (step S 343 ), the control flow returns to step S 341 .  
      In some cases, a broadcasted component includes directory information that describes constructions of presentation elements and reception elements included in this component. The above viewing enabled signal may be contained in such directory information.  
      (6) Restriction on Number of Interactive Data Operations  
      The data operation restricting unit  116  counts a number of operations performed by the user on interactive data, based on an interactive data operation signal. When the counted number of operations reaches a predetermined number, for instance, fifty or higher, the data operation restricting unit  116  ignores the above interactive data operation signal.  
      The following describes the processing of the data operation restricting unit  116  with reference to a flowchart of  FIG. 27 . This processing is basically the same as that shown in  FIG. 14 , and therefore explanation below focuses on steps unique to  FIG. 27 . These steps are assigned reference numbers that are different from those in  FIG. 14 .  
      As soon as the processing starts, the data operation restricting unit  116  initializes a counted number by substituting zero into the counted number (step S 360 ). This initialization in step S 360  may be performed, for instance, as soon as a user selects a viewing of a program for the first time.  
      Immediately after step S 261 , the data operation restricting unit  116  increments the counted number by one (step S 361 ).  
      Immediately before step S 267 , the data operation restricting unit  116  compares the counted number with the number “50” to judge whether the counted number reaches the number “50” (step S 363 ). If so, the control flow returns to either step S 261  or step S 263 . If not, the control flow moves to step S 267 .  
      (7) Restriction Placed on Interactive Data Presentation when Purchase State Signal Indicates Preview State or Viewing Prohibited State  
      The data presentation restricting unit  115  prohibits interactive data from being presented to the user when judging that the purchase state signal sent from the restoring unit  103  indicates the preview state or the viewing prohibited state.  
      The following describes this processing with reference to a flowchart of  FIG. 28 .  
      The data presentation restricting unit  115  receives the first data signal and the purchase state signal from the restoring unit  103  (step S 381 ).  
      Following this, the data presentation restricting unit  115  judges whether the received purchase state signal indicates the viewing permitted state (step S 382 ). If so, the data presentation restricting unit  115  outputs the first data signal and the purchase state signal to the data analyzing unit  104  (step S 383 ), and the control flow returns to step S 381 . The processing is then repeated.  
      When the data presentation restricting unit  115  judges that the received purchase state signal does not indicate the viewing permitted state (step S 382 ), the control flow returns to step S 381 , and the processing is repeated.  
      (8) Restriction Placed on User Operations for Interactive Data when Purchase State Signal Indicates Preview State or Viewing Prohibited State  
      The data operation restricting unit  116  receives the purchase state signal from the data analyzing unit  104 . When this purchase state signal indicates the preview state or the viewing prohibited state, the data operation restricting unit  116  ignores an interactive data operation signal which it has received.  
      The following describes this processing with reference to a flowchart of  FIG. 29 . This flowchart is the same as that of  FIG. 14 , except that the flowchart of  FIG. 29  does not contain step S 266 .  
      As shown in the flowchart, when the data operation restricting unit  116  judges that the purchase state signal does not indicate the viewing permitted state (step S 265 ), the control flow returns to either step S 261  or step S 263 . The processing is then repeated.  
      (9) Other Modifications  
      The present invention may be a method that achieves the processing as described above. The present invention may also be a computer program that has a computer achieve this method, or digital signals for this computer program.  
      The present invention may be the above computer program or digital signals recorded on a computer-readable recording medium, such as a floppy disc, hard disk, a CD-ROM (read only memory), a magneto-optical disc (MO), a DVD (digital versatile disc), a DVD-ROM, a DVD-RAM, and semiconductor memory.  
      For the present invention, the above computer program or the digital signals may be transmitted via a network, which may be represented by a telecommunication network, a wireless or cable network, or the Internet.  
      The present invention may be a computer system that comprises a microprocessor and memory which stores the above computer program, and the microprocessor may execute the stored computer program to achieve the present invention. The above computer program or digital signals may be recorded on the computer-readable recording medium to be distributed via the network or other distribution methods to a computer system.  
      The above embodiment and example modifications may be combined.  
      As has been described, the present invention can restrict viewing of interactive data during a preview time. This therefore prevents the user from viewing all the interactive data during the preview time. In addition, the present invention prohibits interactive data from being presented or operated in the viewing prohibited state. As a result, the user cannot view, in the viewing prohibited state, interactive data that has been stored during the preview time. Further, a program producer can freely determine interactive data operable during a preview time and present the interactive data in a manner that encourages users to purchase a program.  
      Although the present invention has been fully described by way of examples with reference to accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Therefore, unless such changes and modifications depart from the scope of the present invention, they should be construed as being included therein.