Abstract:
A system and method for distributing content data and license information. A distribution server includes a transmitting section for transmitting the content data and the license information, including information regarding a time limit that indicates a period for reproducing the content data, to the one or more receiving terminals. The distribution server also includes a request receiving section for receiving, from the one or more receiving terminals, a request for the content data and a request for the license information a second time without the content data, wherein the request for the license information a second time is transmitted in response to a notice indicating the status of the license information.

Description:
1. TECHNICAL FIELD 
       [0001]    The present invention relates to a content distribution system, a distribution server, a receiving terminal, and a computer readable medium. 
       2. BACKGROUND INFORMATION 
       [0002]    Content distribution services may be used for distributing content data, including movies, music, software, over a network such as the Internet. Generally, a content distribution service may comprise a distribution server and a user terminal which are connected to the network. The distribution server may store content data and may distribute the content data in accordance with access from the user terminal. The user terminal may access the distribution server to download the content data. 
         [0003]    For example, as a technique of downloading content data from the distribution server, JP-A-2000-311416 discloses a technique in which a predetermined item of unnecessary data can be erased automatically among items of content data stored in a receiving terminal. 
         [0004]    Content data downloaded by a receiving terminal may contain a viewing time limit, such as a rental model where the time period for reproduction and the number of reproductions is restricted. In this example, a content distributor can offer content distribution services for the user with a reduced purchase cost like a rental fee for a rental video, as compared with the case of distributing content data with no viewing time limit. 
         [0005]    However, in the case in which content data is downloaded for reproduction, it is necessary to download the content data before reproduction begins because it is not possible to reproduce the content data during downloading. Therefore, when a large amount of data is downloaded, or when a user uses a low speed line, a downloading time period is prolonged and takes much time before a user can view the content data. In addition, since downloaded content data is normally automatically erased from a recording medium on a receiving terminal when a viewing time limit has expired, a user cannot reproduce the content data after expiration. 
         [0006]    Therefore, in the case in which a user is not able to view downloaded content data within a viewing time limit, it is necessary for the user to again download the same content data because the content data is automatically erased from a recording medium on a receiving terminal. In addition, in the case in which a user desires to again view the same content data after a first time purchase period is expired, the user must download the same content data again. This results in an increased content data reproduction time. 
       SUMMARY 
       [0007]    Embodiments of the present invention encompass methods, apparatus, and computer readable mediums for distributing content data and license information. 
         [0008]    Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. 
         [0009]    In one exemplary embodiment, there is provided a method for distributing content data to one or more receiving terminals. The method includes transmitting the content data and the license information, including information regarding a time limit that indicates a period for reproducing the content data, to the one or more receiving terminals. The method also includes receiving, from the one or more receiving terminals, a request for the content data and a request for the license information a second time without the content data, wherein the request for the license information a second time is transmitted in response to a notice indicating the status of the license information. 
         [0010]    In another exemplary embodiment, there is provided a method for receiving content data from a distribution server. The method includes sending a first request, the first request being for the content data, receiving the content data and license information, including information regarding a time limit that indicates a period for reproducing the content data, storing the content data and license information, reproducing the content data during a period of reproduction corresponding to the license information. The method also includes sending a second request, the second request being for the license information without the content data, wherein the second request is transmitted in response to a notice indicating the status of the license information. 
         [0011]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as described. Further features and/or variations may be provided in addition to those set forth herein. For example, the present invention may be directed to various combinations and subcombinations of the disclosed features and/or combinations and subcombinations of several further features disclosed below in the detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The accompanying drawings, which are incorporated in and constitute a part of this specification, show certain aspects of implementations consistent with the present invention and, together with the description, help explain some of the principles associated with the invention. In the drawings, 
           [0013]      FIG. 1  illustrates a block diagram of an exemplary content distribution system, consistent with certain aspects related to the present invention; 
           [0014]      FIG. 2  illustrates an exemplary receiving terminal, consistent with certain aspects related to the present invention; 
           [0015]      FIG. 3A-3B  illustrate flow charts depicting the operation of the content distribution system, consistent with certain aspects related to the present invention; 
           [0016]      FIG. 4  illustrates a download sequence of the content distribution system, consistent with certain aspects related to the present invention; 
           [0017]      FIG. 5A-6B  illustrate sequences of the management of the content data of the content distribution system, consistent with certain aspects related to the present invention; 
           [0018]      FIG. 7  illustrates a reproduction sequence of downloaded content, consistent with certain aspects related to the present invention; and 
           [0019]      FIG. 8  illustrates windows displayed on a screen of a display device connected to the receiving terminal, consistent with certain aspects related to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    The following detailed description refers to the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the following description to refer to the same or similar parts. While several exemplary embodiments and features of the invention are described herein, modifications, adaptations and other implementations are possible, without departing from the spirit and scope of the invention. For example, substitutions, additions or modifications may be made to the components illustrated in the drawings, and the exemplary methods described herein may be modified by substituting, reordering or adding steps to the disclosed methods. Accordingly, the following detailed description does not limit the invention. Instead, the proper scope of the invention is defined by the appended claims. 
         [0021]      FIG. 1  illustrates a block diagram depicting a content distribution system  100 . Content distribution system  100  may distribute content data, including, for example, movies, music, sports, software, over a network such as the Internet. Content distribution system  100  may contain a distribution server  102  and a receiving terminal  140  (i.e. a user terminal) which may be connected to network  120 . Content distribution system  100  may implement content distribution services in which content data is distributed to receiving terminal  140  and receiving terminal  140  may download the content data. 
         [0022]    Network  120  may be a wide area IP network, for example, in which Internet protocol (IP) techniques are used to mutually connect computers to the network. Network  120  may also include closed domain networks. A network modem/rooter  130  may be connected between network  120  and receiving terminal  140 . Network modem/rooter  130  may modulate and demodulate digital signals and analog signals between network  120  and receiving terminal  140 . Network modem/rooter  130  may also connect or relay different computer networks (i.e. controls routes). 
         [0023]    As depicted in  FIG. 1 , distribution server  102  may contain portal server  110 , content server  112 , metadata server  114 , and Digital Rights Management (DRM) server  116 . Distribution server  102  may be configured of separate computer servers such as portal server  110 , content server  112 , metadata server  114 , and DRM server  116 . However, distribution server  102  may be configured of a computer server that is a single piece of hardware having all of the functions of portal server  110 , content server  112 , metadata server  114 , and DRM server  116 . Moreover, portal server  110 , content server  112 , metadata server  114 , and DRM server  116  may each be configured of one or more pieces of hardware. Portal server  110 , content server  112 , metadata server  114 , and DRM server  116  may each contain a Central Processing Unit (CPU), memory, storage, input/output interface (IF), communication IF, and display part. 
         [0024]    The CPU may function as a processor and a control unit that may control processes of all components provided on each server. The memory may contain a storage part (i.e. a RAM (Random Access Memory), a ROM (Read Only Memory), and a cache memory) that may temporarily store data relating to the process of the CPU. The storage part may be implemented by, for example, any combination of a hard disk drive (HDD) and flash memory. The storage part may store data including, for example, user information, terminal performance information, network line information, and a program. 
         [0025]    The input/output IF may contain a mouse, keyboard, touch panel, buttons, one or more switches, lever, and an input control part that may generate input signals and may output them to the CPU. For example, an administrator of distribution server  102  may manipulate the manipulating part of the input/output IF to input data into individual servers or instruct the processing operation of the individual servers. 
         [0026]    Communication IF may contain, for example, communication lines, a communication circuit, and a communication device. Communication IF may send and receive data between individual servers or between the servers and receiving terminal  140  over network  120 . 
         [0027]    The display part may contain, for example, a display device, such as a liquid crystal display (LCD) device, a CRT display device, and a lamp, that may display video signals and a sound output unit, such as a speaker, that may output sound signals. The administrator of distribution server  102  may confirm the manipulation result of the input/output IF through the display part. 
         [0028]    Portal server  110  may offer navigation information regarding a description of the contents used by content distribution services to receiving terminal  140 . Portal server  110  may receive a request, or access, from receiving terminal  140  and may send data from receiving terminal  140  to content server  112 , metadata server  114 , and DRM server  116  in accordance with the request. In addition, portal server  110  may receive data from content server  112 , metadata server  114 , and DRM server  116  and may send the data to receiving terminal  140  over network  120 . In addition, the CPU of portal server  110  may include a transmitting part that may transmit content data to receiving terminal  140 . 
         [0029]    Content server  112  may store content data including, for example, movies, music, sports, pictures, and software, and may send the content data to receiving terminal  140  through portal server  110  in accordance with a request from receiving terminal  140 . 
         [0000]    For example, if content server  112  sends video contents such as movies and sports, content server  112  may encode the content data in accordance with the MPEG-1 Audio Layer-2 (MPEG-2), MPEG-1 Audio Layer-4 (MPEG4), or a QuickTime system and may send the content data to receiving terminal  140 . 
         [0030]    When content server  112  sends contents relating to sound and music, for example, content server  112  may encode the content data in accordance with, for example, an MPEG-1 Audio Layer-3 (MP3) system, an Adaptive Transform Acoustic Coding (ATRAC) system and may send the content data to receiving terminal  140 . However, the coding system is not restricted to the examples above. 
         [0031]    Content server  112  may also send a reproduction control metafile to receiving terminal  140 . The reproduction control metafile may be used when receiving terminal  140  stores the content data and reproduces the content data. In an example regarding video contents, the reproduction control metafile may contain time data that may indicate a starting point of one or more chapters of the content and one or more highlights of the content. 
         [0032]    Metadata server  114  may store metadata relating to the stored content data and may send the metadata to receiving terminal  140  upon request. By way of example, metadata may be data relating to contents including a title, creation date, time, cast, synopsis, genre, and distributable period of the contents. 
         [0033]    DRM server  116  may manage a DRM of the contents. DRM server  116  may receive an issuance request for a license relating to content data from receiving terminal  140 , determine whether receiving terminal  140  satisfies license issuance conditions, and issue the license to receiving terminal  140 . Generally, in receiving terminal  140 , it is not possible to reproduce individual contents using only the content data from content server  112 , and reproduction may be allowed when user conditions for obtaining an adequate license are satisfied. Methods generally used can be adapted to DRM, omitting the detailed descriptions. In DRM, however, methods other than those described above may be used. 
         [0034]    The license may include reproduction time limit information that may contain a reproduction time limit that may limit reproduction of content data downloaded by receiving terminal  140 . The reproduction time limit may be a period of time that allows reproduction, such as a date, or a number of times for allowing reproduction. For example, the period of reproduction may be a predetermined period that begins when receiving terminal  140  receives the content data, regardless of the date and time that receiving terminal  140  receives the content data. The number of times for allowing reproduction may be a predetermined number of times of reproduction that receiving terminal  140  can reproduce the downloaded content data. 
         [0035]    The CPU of DRM server  116  may include a transmitting part and a request accepting part. The transmitting part may send the license including the reproduction time limit information to receiving terminal  140 . The request accepting part may receive a request for distribution of the reproduction time limit information that is sent by receiving terminal  140  based on a user confirmation. The request accepting part may also receive the request for distribution and send a signal to the transmitting part. The transmitting part may send the license to receiving terminal  140  based on the request. 
         [0036]    Receiving terminal  140  may be connected to network  120 . Network  120  may be, for example, a personal computer, a tuner having a radio receiver, a television set, or a set-top box that may receive IP broadcasts viewable over cable television, television broadcasting, or a network. As depicted in  FIG. 2 , receiving terminal  140  may contain CPU  156 , memory  157 , storage  158 , and communication IF  164 . 
         [0037]    Receiving terminal  140  may send a request for the content data to portal server  110  over network  120 . Receiving terminal  140  may receive content data recorded in content server  112 , metadata recorded in metadata server  114 , and the license issued from DRM server  116  through the portal server  110 . Receiving terminal  140  may be connected to display device  180 , a Graphical User Interface (GUI), and an Electronic Content Guide (ECG). 
         [0038]    The GUI may offer a screen on which the content data is displayed so that a user may manipulate the content data. The content data may be electronic books, games, and software. The ECG may use metadata to offer a navigation function (i.e. a list of contents downloadable from distribution server  102 ), a list of contents purchased and viewable on receiving terminal  140 , and detailed information about the contents. 
         [0039]    Display device  180  may display video signals and may be, for example, a display device of a computer terminal or a television set, an LCD device, a plasma display device, a CRT display device, or a sound output unit that may output sound signals (i.e. a speaker). 
         [0040]    Display device  180  is one example of a display and may be connected to receiving terminal  140  to receive data from receiving terminal  140 , may reproduce videos and sounds relating to data, and may display the GUI screen and the ECG screen. Video signals, sound signals, and control signals may be sent between receiving terminal  140  and display device  180  and may be received through an interface including, for example, a High-Definition Multimedia Interface (HDMI). In addition, receiving terminal  140  and display device  180  may be configured of discrete component devices or may be a combination device wherein receiving terminal  140  and display device  180  are contained in one piece. 
         [0041]    Display device  180  may display the reproduction time limit of the downloaded content data along with the list of the contents purchased and viewable on receiving terminal  140 . In addition, display device  180  may display the downloaded content data within the reproduction time limit and may display one or more notices. The notices may, for example, indicate the time remaining for reproduction, that the reproduction time limit is expired, a request for permission to erase the content data, a request for permission to move the content data from the storage section to an external storage section, and that an allowable reproduction period of the content data is not expired. The content data may be erased after a predetermined period (i.e. after expiration of an allowable duration) and may be moved after expiration of an allowable period. 
         [0042]    Display device  180  may also display a confirmation indicating that the license is repurchased before the reproduction time limit has expired. Furthermore, display device  180  may display a confirmation indicating that the content data stored in the storage of the receiving terminal  140  is erased or moved to external storage. 
         [0043]    Remote controller  190  is one example of a manipulating part that may manipulate receiving terminal  140  and may perform remote control at the distance apart from receiving terminal  140 . Remote controller  190  may allow reproduction control of AV player  176  and manipulation on a BML browser or the ECG. The manipulating part for receiving terminal  140  may not be restricted to remote controller  190 , which may be a manipulating part disposed on receiving terminal  140 . 
         [0044]      FIG. 2  illustrates a block diagram of receiving terminal  140 . As illustrated in  FIG. 2 , receiving terminal  140  may contain digital broadcast tuner  142 , communication processing part  144 , Conditional Access System/DRM (CAS/DRM) client part  146 , demultiplexer (DMUX)  148 , decoder  150 , DRM processing part  152 , GUI display processing part  154 , CPU  156 , and storage  158 . 
         [0045]    Digital broadcast tuner  142  may receive digital broadcasts (BS, CS, and ground waves) and may output the digital broadcasts to individual functional blocks of receiving terminal  140 . Digital broadcast tuner  142  may also receive broadcast signals of digital broadcasts through an antenna line broadcast IF  162 . Digital broadcast tuner  142  may be provided on receiving terminal  140 , whereby television broadcasts received through an antenna line and television broadcasts in accordance with IP broadcasts may be viewed. By way of an example, receiving terminal  140  does not have to contain digital broadcast tuner  142 . 
         [0046]    Communication processing part  144  may perform communication control in accordance with the protocols including, for example, Real-time Transport Protocol (RTP), User Datagram Protocol (UDP), Hypertext Transfer Protocol (HTTP)/Transport Layer Security (TLS) in Secure Socket Layer (SSL) (HTTP/TLS), Real Time Streaming Protocol (RTSP), Transmission Control Protocol (TCP), Internet Protocol (IP), and Internet Group Management Protocol/Multicast Listener Discovery (IGMP/MLD). Communication processing part  144  may receive signals through communication IF  164  by, for example, an Ethernet connection and may output the signals to individual functional blocks of receiving terminal  140 . Communication processing part  144  may also process streaming data, sent by UDP, to improve jitter caused by network communication by, for example, Forward Error Correction (FEC) processing. 
         [0047]    CAS/DRM client part  146  may obtain a license from a CAS server or DRM server  116 . CAS/DRM client part  146  may decode received transmission data and content data that are encrypted. CAS/DRM client part  146  may perform contents management of digital broadcasting done in accordance with CAS and may decode content data encrypted in accordance with DRM. In addition, CAS/DRM client part  146  may include a descrambler and a decrypter. CAS/DRM client part  146  may receive data output from digital broadcast tuner  142  or communication processing part  144  and may output the decoded signals to DMUX  148 . 
         [0048]    DMUX  148  may perform a demultiplexer process. DMUX  148  may receive the decoded signals from CAS/DRM client part  146  and may separate the decoded signals into signals including videos, sounds, subtitles, and Program Specific Information/Service Information (PSI/SI). 
         [0049]    Decoder  150  may decode the signals subjected to DMUX  148 . Decoder  150  may contain a video decoder that may decode video data, a sound decoder that may decode audio data, and a subtitle data decoder that may decode subtitle data. 
         [0050]    DRM processing part  152  may output the video signals and the sound signals that are subjected to DMUX  148  for separation to external storage  160  and may encrypt data including the video signals and the sound signals when data is stored in external storage  160 . This encryption process may allow only the appropriate receiving terminal  140  to reproduce content data, which may restrict reproduction by another receiving terminal  140  even though the external storage is connected to the another receiving terminal  140 . Data encrypted in DRM processing part  152  may be output to external storage  160  or a removable medium through IF  166  and IF  168 . External storage  160  may be a hard disk drive, and the removable medium may be a drive unit for optical disks including, for example, a compact disk or a DVD. 
         [0051]    GUI display processing part  154  may perform a reproduction process of data of the video signals decoded in the video decoder and a synthesis process of display data for the browser, EPG, and ECG and may generate data viewable by a user on display device  180 . The data generated in GUI display processing part  154  may be output to display device  180  through video/sound output IF  170 . 
         [0052]    CPU  156  may function as a processor and a control unit by a program, which can control the processes of the individual components provided on the individual servers. CPU  156  may control various applications including the browser activated in receiving terminal  140 , the download of the content data, the storage of the downloaded content data, and the reproduction of content data stored in storage  158 . 
         [0053]    CPU  156  may include a receiving part, a control part, a time limit information requesting part, a confirming part, and a storage control part. The receiving part may receive content data from content server  112  of distribution server  102  and the license including reproduction time limit information sent from DRM server  116 . 
         [0054]    The control part may reproduce content data when content data stored in storage  158  or external storage  160  can be reproduced based on reproduction time limit information, regardless of the timing or the number of times that reproduction time limit information about the license is stored in storage  158 . The time limit information requesting part may send a request for the distribution of reproduction time limit information to the request accepting part of distribution server  102 . 
         [0055]    The confirming part may confirm with a user if it is necessary to distribute reproduction time limit information before the reproduction time limit is expired. In addition, either after the reproduction time limit is expired, before the storage control part erases content data, or when content data is never reproduced by the control part, the confirming part may confirm with a user whether it is necessary to erase the content data. Furthermore, after the reproduction time limit is expired or before the storage control part moves content data to external storage  160 , the confirming part may confirm with a user whether it is necessary to move the content data. Confirmation may be presented to a user by one or more messages or notices displayed on a screen of receiving terminal  140 . 
         [0056]    The storage control part may output the content data, content metainformation, and license metainformation received in the receiving part to storage  158 . In addition, the storage control part may erase the content data, content metainformation, and license metainformation. Furthermore, the storage control part may move the content data, content metainformation, and license metainformation from storage  158  to external storage  160 . Receiving terminal  140  may be connected to external storage  160  via an Ethernet, USB, or eSATA connection and the data is protected and moved in accordance with the protocol (i.e. DTCP/IP). 
         [0057]    Browser  174  and AV player  176  may be activated by CPU  156 . Browser  174  may be a Broadcast Markup Language (BML) browser, which is software that may reproduce contents described in BML. BML may be used to define display control, what, when and where display device  180  is displayed on the screen, descriptions that may describe links showing URLs of related broadcast programs, Internet addresses, titles, and main information, and a user interface such as manipulation buttons. Browser  174  may also display downloadable contents and a list of the contents on display device  180  to allow a user to select contents for downloading. The list of contents stored in storage  158  and already purchased may be displayed to allow a user to select contents desired to reproduce. 
         [0058]    AV player  176  may perform a reproduction process of content data such as video data and audio data. For example, AV player  176  may control operations such as the start and stop of reproduction of content data, forward, rewind, and moving chapters. 
         [0059]    Memory  157  may be configured of a storage part such as a RAM (Random Access Memory), a ROM (Read Only Memory), and a cash memory, having a function that temporarily stores data relating to the process of the CPU and the CPU&#39;s operation programs. 
         [0060]    Storage  158  may record content data downloaded in receiving terminal  140  through the download control process and the storage control process in CPU  156 . Storage  158  may be configured, for example, of any combination of a HDD (hard disk drive) and flash memory. 
         [0061]    Input/output IF  172  may be configured of a manipulating part including a mouse, keyboard, touch panel, buttons, switches, lever, and an input control part that generates input signals and outputs them to the CPU and the other components. For example, a user may manipulate the manipulating part of input/output IF  172  to input data into receiving terminal  140  or to instruct the process operation of receiving terminal  140 . 
         [0062]    Next, the operation of receiving terminal  140  will be described with reference to  FIGS. 3A ,  3 B, and  4 .  FIGS. 3A and 3B  illustrate flow charts depicting the operation of content distribution system  100 .  FIG. 4  illustrates the download sequence of content distribution system  100 . 
         [0063]    Based on manipulation by a user, receiving terminal  140  may access distribution server  102 . At this time, receiving terminal  140  may connect to portal server  110  based on a reference link destination (Step S 102 ). If receiving terminal  140  is authenticated by portal server  110 , receiving terminal  140  may acquire metadata, which may be data relating to an ECG that may contain the title list of downloadable content data from portal server  110  (Step S 104 ). Subsequently, browser  174  of receiving terminal  140  may depict the list including, for example, the title list of the content data, on display device  180  based on the acquired list (Step S 106 ). The list may allow the user to select content data. Then, the user may select desired content data to download and may request downloading of the content data (Step S 108 ). 
         [0064]    Subsequently, based on the download instruction, receiving terminal  140  may access content server  112 , metadata server  114 , and DRM server  116  through portal server  110 . Receiving terminal  140  may acquire content metainformation from metadata server  114  (Step S 110 ), obtain a reproduction control metafile from content server  112  (Step S 112 ), and obtain license metainformation from DRM server  116  (Step S 114 ). 
         [0065]    Receiving terminal  140  may perform a storage control process of the acquired reproduction control metafile and may store the reproduction control metafile in storage  158  (Step S 116 ). Subsequently, receiving terminal  140  may request desired content data from content server  112  and may download the content data (Step S 118 ). 
         [0066]    Receiving terminal  140  may store the downloaded content data in storage  158  (Step S 120 ). After the content data is stored, it may be reproduced when license conditions are satisfied. 
         [0067]    As illustrated in  FIG. 3B , the confirming part provided on receiving terminal  140  may confirm with the user if it is necessary to obtain the license of the content data again (Step S 122 ). If the license is not needed (i.e. in a case where the reproduction time limit of the license simultaneously downloaded with the content data is not expired), the download operation done by receiving terminal  140  is ended. However, it may be necessary to obtain the license again in a case where the reproduction time limit of the license has expired. According to this example, the time limit information requesting part of receiving terminal  140  may access DRM server  116  (Step S 124 ) and request distribution of the license, including reproduction time limit information, again (Step S 126 ). The request accepting part of DRM server  116  may receive the request for distribution and output a signal to the transmitting part of DRM server  116 . The transmitting part may transmit the license to receiving terminal  140 , and receiving terminal  140  may again obtain the license from DRM server  116  (Step S 128 ). 
         [0068]    Next, content data management will be described with reference to  FIGS. 5A ,  5 B,  6 A, and  6 B, which illustrate a sequence of content data management by content distribution system  100 . 
         [0069]    As illustrated in (A) in  FIG. 5A , no reproducible contents are recorded in storage  158  of receiving terminal  140  before receiving terminal  140  downloads content data. When receiving terminal  140  requests the distribution of content data from distribution server  102 , content data and content metainformation are downloaded from content server  112  and license metainformation is downloaded from DRM server  116 . Subsequently, as illustrated in (B) in  FIG. 5A , the content data, content metainformation such as the title relating to the content, and license metainformation including reproduction time limit information may be stored in storage  158  of receiving terminal  140 . At this time, receiving terminal  140  may reproduce the content data as long as the reproduction time limit of the license is satisfied. This illustration is exemplary and receiving terminal  140  may request the distribution of content data from content server  112 , content metainformation from metadata server  114 , and license metainformation from DRM server  116  according to another embodiment. 
         [0070]    Subsequently, as shown in (C) in  FIG. 5B , when the reproduction time limit of the license has expired, the license stored in storage  158  may be erased from storage  158  by the storage control part of receiving terminal  140 . At this time, the content data and content metainformation may remain stored in the storage  158  without being erased. Next, the confirming part provided on receiving terminal  140  may confirm with the user if it is necessary to obtain the license of the content data again. Depending on the user&#39;s desire to view the content data, if it is necessary to obtain the license again, the time limit information requesting part may request distribution of the license, and the DRM server  116  may send only the license to receiving terminal  140 . Then, as illustrated in (D) in  FIG. 5B , the license is again stored in storage  158 , and the content data may be reproduced as long as the reproduction time limit of the license is satisfied. 
         [0071]    As described above, even though the reproduction time limit of the license once obtained is expired, content data and content metainformation may not be erased. Thus, only the license is obtained again to reproduce content data stored in the storage  158 . Therefore, since it is unnecessary to again download content data, the content may be readily viewed within a short period of time. 
         [0072]    As illustrated in (A) in  FIG. 6A , the content data may remain in storage  158 . However, the available capacity of storage  158  decreases because of the stored content data. Therefore, as illustrated in (B) in  FIG. 6A , the storage control part of receiving terminal  140  may move the content data and content metainformation to external storage  160 . In addition, the storage control part may erase the content data and content metainformation stored in storage  158 . Moreover, the confirming part of receiving terminal  140  may confirm with a user if it is necessary to erase or move the content data before the storage control part erases or moves the content data. As described above, the content data may be moved to external storage  160  with no reduction in the capacity of storage  158 . 
         [0073]    As illustrated in (C) in  FIG. 6B , the confirming part provided on receiving terminal  140  may confirm with the user if it is necessary to obtain the license of the content data again. When it is necessary to again obtain the license, the time limit information requesting part may request distribution of the license. Then, as shown in (D) in  FIG. 6B , DRM server  116  may transmit only the license to receiving terminal  140 , and the license may be stored in external storage  160  or storage  158 , not shown, of receiving terminal  140 . Consequently, receiving terminal  140  may reproduce content data stored in external storage  160  as long as the reproduction time limit of the license is satisfied. 
         [0074]    The reproduction operation of the downloaded content data will be described with reference to  FIG. 7 . Browser  174  may display the list of reproducible content data recorded in storage  158 . The list may allow a user to select content data (Step S 202 ). 
         [0075]    When a reproducible content is selected, AV player  176  may be activated to reproduce contents. If the license is not stored in storage  158 , AV player  176  may request the license, including a reproduction time limit, from DRM server  116  (Step S 204 ). DRM server  116  may determine if receiving terminal  140  satisfies the conditions for issuing the license (i.e. the completion of the purchase process). DRM server  116  may issue the license if the conditions are satisfied (Step S 206 ). After receiving terminal  140  receives the license from DRM server  116 , receiving terminal  140  may reproduce content data within the reproduction time limit (Step S 208 ). 
         [0076]      FIG. 8  illustrates an exemplary window displayed on display device  180 . As illustrated, titles of downloaded content data stored in receiving terminal  140  may be displayed in a list on the window. 
         [0077]    As illustrated in (A), Contents A to Contents E may be, for example, title names of the content that may depict a time period required for reproducing each of the contents and a reproducible time limit (i.e. month and day) based on a license of each content. When a cursor is moved to select content whose license is obtained again, a message “reproduce the content by the decision key” may be displayed on the lower part of the screen. A decision key may be selected to reproduce the content. 
         [0078]    (B) and (C) in  FIG. 8  illustrate examples when content stored in external storage  160  is displayed in a list. As illustrated in (B), when a cursor is moved to select a content, a message stating “again obtain the license by the decision key” may be displayed on the lower part of the screen. The message may be displayed before the license expires or after the expiration of the license. If the message is selected, receiving terminal  140  may transmit a request to DRM server  116  for the license information without re-sending the content. In response, DRM server  116  may transmit the license information a second time to receiving terminal  140 . 
         [0079]    As illustrated in (C), when the license is obtained a second time, the reproduction time limit is depicted on the list of the contents. When a cursor is moved to select a content whose license is already obtained again, a message stating “reproduce the content by the decision key” may be displayed on the lower part of the screen. This decision key may be selected to reproduce the content. 
         [0080]    The preferred embodiment according to the invention has been described with reference to the accompanying drawings, and it is without saying that the invention is not restricted to these examples. It will be apparent to those skilled in the art that various modifications or alternations can be conceived within the teachings described in the scope of claims, and it should be understood that they of course belong to the technical scope of invention. 
         [0081]    The foregoing description has been presented for purposes of illustration. It is not exhaustive and does not limit the invention to the precise forms or embodiments disclosed. Modifications and adaptations of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed embodiments of the invention. For example, the described implementations include software, but systems and methods consistent with the present invention may be implemented as a combination of hardware and software or in hardware alone. Examples of hardware include computing or processing systems, including personal computers, servers, laptops, mainframes, micro-processors and the like. Additionally, although aspects of the invention are described for being stored in memory, one skilled in the art will appreciate that these aspects can also be stored on other types of computer-readable media, such as secondary storage devices, for example, hard disks, magnetic disks, optical disks, solid state memory, or other forms of RAM or ROM. 
         [0082]    Computer programs based on the written description and methods of this invention are within the skill of an experienced developer. The various programs or program modules can be created using any of the techniques known to one skilled in the art or can be designed in connection with existing software. 
         [0083]    Moreover, while illustrative embodiments of the invention have been described herein, the scope of the invention includes any and all embodiments having equivalent elements, modifications, omissions, combinations (e.g., of aspects across various embodiments), adaptations and/or alterations as would be appreciated by those in the art based on the present disclosure. The limitations in the claims are to be interpreted broadly based on the language employed in the claims and not limited to examples described in the present specification or during the prosecution of the application, which examples are to be construed as non-exclusive. Further, the steps of the disclosed methods may be modified in any manner, including by reordering steps and/or inserting or deleting steps, without departing from the principles of the invention. It is intended, therefore, that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims and their full scope of equivalents.