Patent Publication Number: US-2016241631-A1

Title: Image management system, communication system, non-transitory recording medium, and image management method

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The disclosures herein generally relate to an image management system, a communication system, a non-transitory recording medium having a program recorded therein that is executable by a computer, and an image management method. 
     2. Description of the Related Art 
     In order to meet requests for reducing expenses and times for business trips, a communication system for performing a conversation (communication) or a conference via a communication network such as the Internet and a private line is popular. In the communication system, when the communication is started between communication terminals, the communication between bases is performed by transmitting/receiving image data, sound data, and the like. Further, for performing the communication between the bases smoothly, in addition to content for the conversation, a method for sharing other content between the bases is known in the art. 
     Japanese Unexamined Patent Application Publication No. 2004-221842 discloses a technique for performing transmitting/receiving sound between a plurality of terminal apparatuses and for controlling a session in order to perform transmitting/receiving an image and handwritten data between the terminal apparatuses. Thus, the technique enables to perform sound conversation while a user is pointing at the image. 
     Using the technique disclosed in Japanese Unexamined Patent Application Publication No. 2004-221842, the session such as a remote class can be held between the bases apart from each other. When the remote class is conducted using the above communication system, there is a case in which a continuation of the remote class is required to be conducted with black board information of the remote class performed previously. However, it is difficult to select and use image information of the previous session from pieces of image information recorded by unspecified users when a session such as the remote class is held using a shared communication terminal, even if handwritten image information has been recorded. 
     As described above, when the session such as the remote class is held using the shared communication terminal such as an interactive white board, it is difficult to restart the session using the image information of the session recorded in the past. 
     SUMMARY OF THE INVENTION 
     It is a general object of at least one embodiment of the present invention to provide an image management system, a communication system, a non-transitory recording medium having a program recorded therein that is executable by a computer, and an image management method that substantially obviate one or more problems caused by the limitations and disadvantages of the related art. 
     An embodiment of the present invention provides an image management system for transmitting information via a session established between communication terminals including a storage unit configured to store image information of an image output from at least one of a first communication terminal and a second communication terminal in a first session in which the first communication terminal and the second communication terminal have participated, the storage unit storing the image information in association with identification information of the first session and a transmission unit configured to transmit, to the first communication terminal and the second communication terminal, the image information stored in the storage unit and associated with the identification information of the first session when the first communication terminal and the second communication terminal participate in a second session which differs from the first session. 
     An embodiment of the present invention also provides a non-transitory recording medium having a program recorded therein that is executable by a computer, the program when executed causing the computer to implement functions of a storage unit configured to store image information of an image output from at least one of a first communication terminal and a second communication terminal in a first session in which the first communication terminal and the second communication terminal have participated, the storage unit storing the image information in association with identification information of the first session and a transmission unit configured to transmit, to the first communication terminal and the second communication terminal, the image information stored in the storage unit and associated with the identification information of the first session when the first communication terminal and the second communication terminal participate in a second session which differs from the first session. 
     An embodiment of the present invention also provides an image management method for transmitting information via a session established between communication terminals including a step of storing, in a storage unit, image information of an image output from at least one of a first communication terminal and a second communication terminal in a first session in which the first communication terminal and the second communication terminal have participated, the storage unit storing the image information in association with identification information of the first session and a step of transmitting, to the first communication terminal and the second communication terminal, the image information stored in the storage unit and associated with the identification information of the first session when the first communication terminal and the second communication terminal participate in a second session which differs from the first session. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a drawing illustrating a configuration example of a communication system according to an embodiment; 
         FIG. 2  is an external view of an interactive white board (IWB) according to the embodiment; 
         FIG. 3  is a drawing illustrating an example of a hardware configuration of the IWB and a communication terminal according to the embodiment; 
         FIG. 4  is a drawing illustrating an example of a hardware configuration of a computer according to the embodiment; 
         FIG. 5  is a drawing illustrating an example of a hardware configuration of an information terminal according to the embodiment; 
         FIG. 6  is a drawing illustrating a functional configuration of the communication system according to the embodiment; 
         FIG. 7  is a drawing illustrating an example of functional configuration of an image information management unit and a session management unit according to the embodiment; 
         FIGS. 8A and 8B  are drawings illustrating examples of an authentication management table and a terminal management table according to the embodiment; 
         FIG. 9  is a drawing illustrating an example of a session management table according to the embodiment; 
         FIG. 10  is a sequence chart illustrating an example of an authentication process according to the embodiment; 
         FIG. 11  is a sequence chart illustrating an example of an establishment process of a session according to the embodiment; 
         FIG. 12  is a sequence chart illustrating an example of an accumulation process of image information according to the embodiment; 
         FIG. 13  is a drawing illustrating an example of an image information management table according to the embodiment; 
         FIG. 14  is a sequence chart illustrating an example of a restoring process of the image information according to the embodiment; 
         FIG. 15  is a drawing illustrating an example of a selecting screen of history of the image information according to the embodiment; 
         FIG. 16  is a drawing illustrating an example of a displaying screen of the communication terminal according to the embodiment; 
         FIG. 17  is a sequence chart illustrating an example of a process after the image information is restored according to the embodiment; and 
         FIG. 18  is a drawing illustrating another configuration example of the communication system according to the embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following, embodiments of the present invention will be described with reference to the accompanying drawings. 
     &lt;System Configuration&gt; 
       FIG. 1  is a drawing illustrating a configuration example of a communication system  100  according to an embodiment of the present invention. The communication system  100  includes a communication management system  101 , a plurality of communication terminals  102   a ,  102   b ,  102   c ,  102   d , and  102   e , a relay apparatus  103  and the like which are connected to a network  104  such as the Internet and a local area network (LAN). In the following, an arbitrary communication terminal (communication device) of the communication terminals  102   a  to  102   e  is referred to as the communication terminal  102 ″. 
     The communication management system (image management system)  101  is an information processing apparatus which manages a session, which is held in the communication system  100 , such as a remote class and a TV conference. For example, the communication management system  101  may perform login authentication of the communication terminals  102   a  to  102   e , management of a connection status, connection control of a session start and a session end, management of various kinds of information and the like. 
     The communication terminals  102   a  to  102   e  are examples according to the present embodiment. The communication terminal  102  may be a wide use information terminal such as a personal computer (PC), a tablet terminal, and a smartphone for example. The communication terminal  102  may be a special (private) communication terminal such as a TV conference apparatus. Further, the communication terminal  102  may be an interactive whiteboard (referred to as the IWB hereinafter) or the like. The IWB may share image information which is input by handwriting with other terminals  102  which participate in the session. It should be noted that in a case in which a wide use information processing apparatus is used for the communication terminal  102 , each function of the communication terminal  102  may be, for example, implemented by application programs which corresponds to the communication system  100  installed in the communication terminal  102 . 
     In the example in  FIG. 1 , the communication terminals  102   a  and  102   e  are PCs, the communication terminals  102   b  and  102   c  are IWBs, the communication terminal  102   d  is the information apparatus such as a the tablet terminal and the smartphone. In the following descriptions, the IWB (communication terminal  102   b  and  102   c ) according to the present embodiment includes a camera, a microphone, a speaker and the like internally or externally and can transmit/receive sound and images similar to another communication terminal  102 . 
     According to the above described configuration, in the communication system  100  according to the present embodiment, a user of the communication terminal  102  may conduct the session such as the remote class and the TV conference with another user of the communication terminal  102 , for example, using images and sound performed transmitting/receiving in real time. Further, the communication terminals  102  may share image information such as a character, a figure, and a symbol which are input by handwriting. 
     For example, in  FIG. 1 , an instructor of the remote class can use the communication terminal  102   a  installed in a base A  105  in order to conduct the remote class for one or more students at the communication terminal  102   b  installed in a base B  106 . At that time, image information (such as a character, a figure, and a symbol which are input by handwriting) input from the communication terminal  102   a  by the instructor at the base A  105  is displayed in the communication terminal  102   b  at the base B  106 . Similarly, the image information input from the communication terminal  102   b  by the student at the base B  106  is displayed in the communication terminal  102   a  at the base A  105 . 
     At that time, the communication management system  101  according to the present embodiment records the image information input in the communication terminals  102   a  and  102   b  in an image information database (DB). Further, for example, the instructor of the remote class can call out (select), from pieces of image information recorded in the image information DB, image information which has been recorded in a previous remote class when conducting the remote class again between the communication terminal  102   a  and the communication terminal  102   b . In this way, the instructor of the remote class can conduct a continuation of the previous remote class. 
     Further, as another example, the instructor of the remote class may use the communication terminal  102   b  installed in the base B  106  in order to conduct the remote class for the plurality of students at the base C  107  connected to the communication terminals  102   c ,  102   d ,  102   e , and the like. At that time, image information input from the communication terminal  102   b  by the instructor at the base B 106 B is displayed in the communication terminals  102   c ,  102   d , and  102   e  at the base C 107 . Similarly, image information input from the communication terminal  102   c  by the student at the base C 107  is displayed in the communication terminal  102   b  at the base B 106  and the communication terminal  102   d  and  102   e  at the base C 107 . 
     It should be noted that the remote class is an example of a predetermined session held by the communication system  100 . The predetermined session held by the communication system  100  may be a conference, a presentation or the like. Moreover, for example, a communication terminal such as a projector and an electronic signboard (digital signage) other than the communication terminals  102   a  to  102   e  may be arranged in each of the bases  105 A,  105 B, and  107 C in a communicable (able to communicate) manner. 
     &lt;Hardware Configuration&gt; 
     Next, a hardware configuration of the present embodiment will be described. 
     (External View of IWB) 
       FIG. 2  is an external view of an interactive white board (IWB) according to the present embodiment. It should be noted that the IWB is an example of the communication terminal  102 . 
     The IWB  200  (the communication terminals  102   b  and  102   c ) may include, for example, a display  201 , a stand (holder)  202 , and an equipment storage unit  203 . The display  201  may include a flat panel such as a liquid crystal panel and a plasma panel. On a front face of the display  201 , a display face  204  which displays an image and a touch panel  205  are arranged. 
     Further, the IWB  200  may include a camera  206  which captures an image of the remote conference, the TV conference and the like, a speaker  207  which outputs sound, a microphone  208  which obtains sound, and the like on the display  201 , for example. Alternatively, the camera  206 , the speaker  207 , the microphone  208  and the like may be structures external to the IWB  200 . 
     An input device  209  includes a signal transmission device. When a pen nib touches the display surface  204 , the signal transmission device transmits a note detection signal (a touch detection signal) as a radio signal. In response to an event that the note detection signal transmitted from the input device  209  is received by the IWB  200 , the display  201  displays the character, the figure, and the like which are written in a coordinate position detected by the touch panel  205 . 
     Further, when a pen root touches the display surface  204 , the signal transmission device transmits a deletion detection signal (a touch detection signal) as a radio signal. In response to an event in which the deletion detection signal transmitted from the input device  209  is received by the IWB  200 , the display  201  eliminates, from the display surface  204 , the character, the figure, and the like which are written in the coordinate position detected by the touch panel  205 . 
     The equipment storage unit  203  may store various kinds of equipment such as a main body of the IWB  200 , for example. Further, on an upper face of the equipment storage unit  203 , a keyboard  210  for performing an input operation is mounted. 
     (Hardware Configuration of IWB) 
       FIG. 3  is a drawing illustrating an example of a hardware configuration of the IWB  200  according to the present embodiment. The IWB  200  includes a central processing unit (CPU)  301 , a read only memory (ROM)  302 , a random access memory (RAM)  303 , a flash memory  304 , a solid state drive (SSD)  305 , a medium drive  307 , and a keyboard  308 . Further, the IWB  200  includes a power switch  309 , a network interface (I/F)  311 , a camera  206 , an imaging element interface (I/F)  312 , the speaker  207 , the microphone  208 , a sound interface (I/F)  313 , the display  201 , and a display (I/F)  314 . Moreover, the IWB  200  includes the touch panel  205 , a touch panel interface (I/F)  315 , a signal reception device  316 , an external device interface (I/F)  317 , an alarm lamp  318 , a bus  310  and the like. 
     For example, the CPU  301  may be an arithmetic and logic unit which reads a program and/or data from the ROM  302  and/or the flash memory  304 , and executes processes according to the program and/or the data to implement various functions of the IWB  200 . The ROM  302  is a non-volatile memory which previously stores a program such as an initial program loader (IPL) used for starting the CPU  301 . The RAM  303  is a volatile memory used as a work area of the CPU  301  or the like. 
     For example, the flash memory  304  may be a storage device which stores an operating system (OS), application programs, various data, and the like. The SSD  305  controls reading of the various data from the flash memory  304  and writing of the various data to the flash memory  304  according to the control by the CPU  301 . A medium drive  307  may control reading of the various data from a recording medium  306  and writing (storing) of the various data to the recording medium  306 , for example. The recording medium may be a memory card. 
     The keyboard  308  is an input device for receiving an operation by a user of the IWB  200 . The power switch  309  is a switch for switching the power of the IWB  200  between on and off. The network I/F  311  is a communication interface for transmitting data using the network  104 . 
     The camera  206  may include an imaging element for capturing an object according to the control of the CPU  301  such as a complementary metal oxide semiconductor (CMOS), a charge coupled device (CCD), or the like. The imaging element (I/F)  312  controls the capturing by the camera  206  and converts the captured data into predetermined image data. The speaker  207  coverts sound signals into sound in order to output the sound. The microphone  208  converts the acquired sound into electrical signals. The sound (I/F)  313  controls input/output of the speaker  207  and the microphone  208 . 
     The display  201  may be an example of a display device such as a liquid crystal display (LCD). The display (I/F)  314  controls displaying of the image by the display  201  according to the control of the CPU  301 . 
     The touch panel  205  is an input device for receiving an input by the input device  209 . The touch panel (I/F)  315  is a control interface used for the touch panel  205 . The signal reception device  316  receives the touch detection signal transmitted from the input device  209 , and outputs the touch detection signal to the touch panel  205 . 
     The external device (I/F)  317  is an example of an interface such as a universal serial bus (USB) for connecting various external devices. The alarm lamp  318  includes a light emitting element for notifying (signaling) abnormality of each of the various functions of the IWB  200  or the like. The bus  310  electrically connects the above described configuration elements to each other, and transmits (transfers) address signals, data signals, various control signals and the like. 
     According to the above described configuration, a touch panel driver which is a control circuit of the touch panel  205  can recognize that an input operation is performed based on the touch detection signal transmitted from the input device  209 , and output the image information (stroke information) which corresponds to the input operation by the input device  209 . Further, the display  201  outputs the image information which is output by the touch panel driver in response to the input operation, and the image based on the image information transmitted from the communication terminal  102  via the network  104  in a superimposing manner. 
     (Hardware Configuration of Communication Management System) 
     The communication management system  101  shown in  FIG. 1  includes a hardware configuration of a typical computer. It should be noted that a hardware configuration of the relay apparatus  103  may be similar to the hardware configuration of the communication management system  101 . 
       FIG. 4  is a diagram illustrating an example of the hardware configuration of a computer  400  according to the present embodiment. The computer  400  includes a CPU  401 , a ROM  402 , a RAM  403 , a HD (Hard Disk)  404 , an HDD (Hard Disk Drive)  405 , a media drive  407 , a display  408 , a network I/F  409 , a keyboard  411 , a mouse  412 , an optical drive  414 , a bus  410 , and the like. 
     For example, The CPU  401  may be an arithmetic and logic unit which reads a program and/or data from the ROM  402  and/or the HD  404 , and executes processes according to the program and/or the data to implement various functions of the computer  400 . The ROM  402  is a non-volatile memory which previously stores a program such as an initial program loader (IPL) used for starting the CPU  401 . The RAM  403  is a volatile memory used as a work area of the CPU  401  or the like. 
     For example, the HD  404  may be a storage application programs, various data, and the like. The HDD  405  controls reading of the various data from the HD  404  and writing of the various data to the HD  404  according to the control by the CPU  301 . The display  408  is a display device which displays various kinds of information such as a cursor, a menu, a window, text, an image, and the like. 
     The network I/F  409  is an interface for communicating data by using the network  104 . The keyboard  411  is an example of an input device for receiving an operation such as text, a numerical value, and various instructions by the user of the IWB  200 . The mouse  412  is an example of a pointing device for receiving an operation such as selection and execution of various kinds of commands, selection of processing target, and movement of the cursor. 
     The medium drive  407  controls reading of data to the recording medium  406  and writing of data from the recording medium  406 , for example. The recording medium  406  may be a memory card. The optical drive  414  controls reading of data from the optical disk  413  and writing of data to the optical disk  413 . The optical disk  413  is an example of a detachable recording medium. The bus  410  electrically connects the above described configuration elements to each other, and transmits address signals, data signals, various control signals and the like. 
     It should be noted that the hardware configuration of the computer  400  is an example, and the present invention is not limited to this. For example, the display  408 , the keyboard  411 , the mouse  412 , and the like may be structures external to the computer  400 . 
     (Hardware Configuration of Information Terminal) 
     Next, a configuration of an information terminal which is the communication terminal  102  such as the communication terminal  102   a ,  102   d , and  102   e  other than the IWB  200  will be described. 
       FIG. 5  is a diagram illustrating an example of a hardware configuration of an information terminal  500  according to the present embodiment. It should be noted that the information terminal  500  may be an information processing apparatus such as a desktop PC, a notebook PC, a tablet terminal, and a smartphone. The information terminal  500  includes a configuration of a typical computer. In an example  FIG. 5 , the information terminal  500  includes a CPU  501 , a RAM  502 , a ROM  503 , a storage unit  504 , an external interface (I/F)  505 , a communication unit  506 , a camera unit  507 , a microphone unit  508 , a speaker unit  509 , a display unit  510 , an input unit  511 , a bus  512 , and the like. 
     The CPU  501  may be an arithmetic and logic unit which reads a program and/or data from the ROM  503  and/or the storage unit  504 , loads the program and/or the data in the RAM  504 , and executes processes according to the program and/or the data to implement various functions of the information terminal  500 . The RAM  502  is a volatile memory used as a work area of the CPU  501  or the like. The ROM  502  is a non-volatile memory which can store programs and/or data even when the power is turned off. For example, the storage unit  504  may be a storage device such as a HDD, a SSD and a flash ROM and store an operating system (OS), application programs, various data, and the like. 
     The external I/F  505  is an interface for connecting external devices. The communication unit  506  is a communication interface for communicating data by using the network  104 . 
     The camera unit  507  includes an imaging element for capturing an image and converts the captured image into predetermined image data. The microphone unit  508  includes a sound acquisition element such as a microphone, converts the acquired sound into electrical signals, and converts the electrical signals into predetermined sound data. The speaker unit  509  coverts the sound signals, which are input, into sound in order to output the sound. 
     The display unit  510  may include a display element such as a liquid crystal display (LCD) and display a displaying screen according to a program executed in the information terminal  500 . The input unit  511  may include an input element such as a touch panel and a keyboard for receiving an input operation by the user. It should be noted that the display unit  510  and the input unit  511  may be, for example, a display input unit  513  such as an integrated touch panel display. The bus  512  is connected to each of the above elements, and transmits address signals, data signals, various control signals, and the like. 
     It should be noted that the hardware configuration of the information terminal  500  is an example, and the present invention is not limited to this. For example, at least one of the display unit  510 , the bus  512 , the camera unit  507 , the microphone unit  508 , and the speaker unit  509  may be disposed outside of the information terminal  500 . 
     &lt;Functional Configuration&gt; 
     Next, a functional configuration of the communication system  100  according to the present embodiment will be described. 
       FIG. 6  is a diagram illustrating a functional configuration of the communication system  100  according to the present embodiment. The communication system  100  includes the communication management system  101 , the communication terminals  102  and the relay apparatus  103 , each of which is connected to the network  104 . 
     In  FIG. 6 , the communication management system  101  manages communications between the communication terminals  102 . The communication terminals  102  can perform the communication according to the management of the communication management system  101  via the relay apparatus  103 . 
     The relay apparatus  103  relays information such as an image and sound transmitted/received between the communication terminals  102 . 
     (Functional Configuration of Communication Terminal) 
     The communication terminal  102  includes a transmission/reception unit  612 , an operation input reception unit  613 , a display unit  614 , a display control unit  615 , a communication control unit  616 , an image/sound input/output unit  617 , a storage/readout unit  618 , a storage unit  619 , and the like. 
     The transmission/reception unit  612  is a unit (means) for transmitting various data (or information) to other communication terminals  102 , the relay apparatus  103 , and the like and receiving the various data from the other communication terminals  102 , the relay apparatus  103 , and the like. In a case in which the communication terminal  102  is the IWB  200 , the transmission/reception unit  612  is realized by programs executed by the CPU  301  shown in  FIG. 3 , the network I/F  311 , and the like. Further, in a case in which the communication terminal  102  is the information terminal  500 , the transmission/reception unit  612  is realized by programs executed by the CPU  501  shown in  FIG. 5 , the communication unit  506 , and the like. 
     The operation input reception unit  613  receives an input operation, a selection operation, and the like from the user. In the case in which the communication terminal  102  is the IWB  200 , the operation input reception unit  613  is realized by programs executed by the CPU  301  shown in  FIG. 3 , the keyboard  308 , the touch panel  205 , the touch panel (I/F)  315 , the signal reception device  316  and the like. Further, in the case in which the communication terminal  102  is the information terminal  500 , the operation input reception unit  613  is realized by programs executed by the CPU  501  shown in  FIG. 5 , the input unit  511  (or the display input unit  513 ), and the like. 
     The display unit  614  is a unit (means) for displaying a display image in accordance with control of the display control unit  615 . In the case in which the communication terminal  102  is the IWB  200 , the display unit  614  is realized by the display  201  and the like. Further, in the case in which the communication terminal  102  is the information terminal  500 , the display unit  614  corresponds to the display unit  510  shown in  FIG. 5 . 
     For example, the display control unit  615  may perform control for displaying, in the display unit  614 , image information transmitted from the communication terminal  102 , which is a communication partner, and image information which is input in own apparatus. In the case in which the communication terminal  102  is the IWB  200 , the display control unit  615  is realized by programs executed by the CPU  301  shown in  FIG. 3 , the display (I/F)  314  and the like. Further, in the case in which the communication terminal  102  is the information terminal  500 , the display control unit  615  is realized by programs executed by the CPU  501  shown in  FIG. 5 , and the like. 
     The communication control unit  616  may perform various kinds of communication controls such as a login process to the communication management system  101 , establishment of the session and disconnection. In the case in which the communication terminal  102  is the IWB  200 , the communication control unit  616  is realized by programs executed by the CPU  301  shown in  FIG. 3 . Further, in the case in which the communication terminal  102  is the information terminal  500 , the communication control unit  616  is realized by programs executed by the CPU  501  shown in  FIG. 5 . 
     The image and sound input/output unit  617  may perform a sound input/output process of the remote class, the TV conference and the like. The image and sound input/output unit  617  may also perform an input process of an image (such as video of meeting) of the session. In the case in which the communication terminal  102  is the IWB  200 , the image and sound input/output unit  617  is realized by programs executed by the CPU  301  shown in  FIG. 3 , the imaging element (I/F)  312 , the sound (I/F)  313  and the like. Further, in the case in which the communication terminal  102  is the information terminal  500 , the image and sound input/output unit  617  is realized by programs executed by the CPU  501  shown in  FIG. 5 , the camera unit  507 , the microphone unit  508 , the speaker unit  509  and the like. 
     The storage/readout unit  618  may perform control of writing of various data to the storage unit  619  and reading of various data from the storage unit  619 . In the case in which the communication terminal  102  is the IWB  200 , the storage/readout unit  618  is realized by programs executed by the CPU  301  shown in  FIG. 3 , the SSD  305  and the like. Further, in the case in which the communication terminal  102  is the information terminal  500 , the image and sound input/output unit  617  is realized by programs executed by the CPU  501  shown in  FIG. 5 , and the like. 
     The storage unit  619  is a unit (means) for storing the various data, information, and the like. In the case in which the communication terminal  102  is the IWB  200 , the storage unit  619  is realized by the RAM  303 , the flash memory  304  shown in  FIG. 3 , and the like. Further, in the case in which the communication terminal  102  is the information terminal  500 , the storage unit  619  is realized by the RAM  502 , the storage unit  504  shown in  FIG. 5 , and the like. 
     (Functional Configuration of Communication Management System) 
     The communication management system  101  includes a transmission/reception unit  601 , an authentication unit  602 , a status management unit  603 , a session management unit  604 , an image information management unit  605 , a storage/readout unit  606 , a storage unit  607 , and the like. 
     The transmission/reception unit  601  is a unit (means) for transmitting various data (or information) to the communication terminals  102 , the relay apparatus  103 , and the like and receiving the various data from the other communication terminals  102 , the relay apparatus  103 , and the like, via the network  104 . The transmission/reception unit  601  is realized by programs executed by the CPU  401  shown in  FIG. 4 , the network I/F  409 , and the like. 
     The authentication unit  602  may perform authentication of the communication terminal  102  by determining whether a communication ID and a password which are included in a login request received from the communication terminal  102  via the transmission/reception unit  601  are included in an authentication management DB  608  stored in the storage unit  607 . The authentication unit  602  may be realized by programs executed by the CPU  401  shown in  FIG. 4 . 
     The status management unit  603  manages operational status (such as communicating, communicable (be able to communicate), not available) of each of the communication terminals  102  included in the communication system  100  using a terminal management unit  609  stored in the storage unit  607 . The status management unit  603  may be realized by programs executed by the CPU  401  shown in  FIG. 4 . 
     The session management unit  604  may be realized by programs executed by the CPU  401  shown in  FIG. 4 . For example, the session management unit  604  may include a session control unit  701  and a session information management unit  702  as shown in  FIG. 7 .  FIG. 7  is a drawing illustrating an example of a functional configuration of the image information management unit  605  and the session management unit  604  according to the present embodiment. 
     The session control unit  701  may control the establishment of the session, such as the remote class and the remote conference, between the communication terminals. The session control unit  701  may also perform connection control of the session such as participation of the communication terminal  102  into the established session and disconnection of the session. 
     The session information management unit (management unit)  702  manages, in the session established between the communication terminals  102 , identification information of the session (session ID) and identification information of the communication terminals  102  which participates in the session (communication ID) in association with each other. For example, the session information management unit  702  records the session ID in which the communication terminal  102   a  and the communication terminal  102   b  shown in  FIG. 1  participate, the communication ID of the communication terminal  102   a , and the communication ID of the communication terminal  102   b  in a session management DB  610  in association with each other. In this way, the communication management system  101  may easily obtain a list of one or more session IDs in which the communication terminal  102   a  and the communication terminal  102   b  participated in the past. 
     The image information management unit  605  shown in  FIG. 6  may be realized by programs executed by the CPU  401  shown in  FIG. 4 . For example, the session management unit  604  may include an obtain control unit  703 , an image information transmission unit  704 , an image information recording unit  705 , and the like as shown in  FIG. 7 . 
     Among information transmitted in the session established between the communication terminals  102 , the image information recording unit  705  records, in the image information DB  611 , at least image information of an image displayed (output) in the communication terminals  102  in association with the session ID. 
     For example, the image information recording unit  705  may record, in the session in which the communication terminal  102   a  and the communication terminal  102   b  shown in  FIG. 1  participate, the image information which is output from the communication terminal  102   a  and the communication terminal  102   b  in association with the session ID. Further, the image information recording unit  705  may record (store), in the session in which the communication terminal  102   a  and the communication terminal  102   b  participate, the image information which is input in the communication terminal  102   a  and the image information which is input in the communication terminal  102   b  in the image information DB  611  in association with the session ID. 
     The obtain control unit  703  obtains, in the session in which the communication terminal  102   a  and the communication terminal  102   b  participate, the image information of the session in which the communication terminal  102   a  and the communication terminal  102   b  participated in the past based on the communication ID of the communication terminal  102   a  and the communication ID of the communication terminal  102   b.    
     For example, the obtain control unit (obtain unit)  703  may transmit, to the communication terminal  102   a , in the session in which the communication terminal  102   a  and the communication terminal  102   b  participate, the information of the one or more sessions in which the communication terminal  102   a  and the communication terminal  102   b  participated, among the sessions whose image information are recorded. Further, the obtain control unit  703  may obtain, from the image information DB  611 , the information of the session to be transmitted to the communication terminals  102  which participate in the session, based on the information received from the communication terminal  102   a  which designates one session among the one or more sessions. 
     The image information transmission unit (transmission unit)  704  transmits, in a second session (when a second session is held), the image information of a first session in which the communication terminal  102   a  and the communication terminal  102   b  have participated among the one or more sessions stored in the image information DB  611  to the communication terminals  102  which participate the second session. For example the image information transmission unit  704  may transmit the image information of the first session which is obtained by the obtain control unit  703  from the image information DB  611  to the communication terminal  102   a  which participates in the second session. The image information of the first session transmitted to the communication terminal  102   a  is displayed in the communication terminal  102   a . Further, the image information of the first session is also transmitted to another communication terminal  102  such as the communication terminal  102   b  with which the image information is shared. 
     The storage/readout unit  606  stores various data in the storage unit  607  and reads out the various data from the storage unit  607 , for example. The storage/readout unit  606  may be realized by programs executed by the CPU  401  shown in  FIG. 4 , for example. 
     The storage unit  607  may be a unit (means) for storing various kinds of information and data which include the authentication management DB  608 , the terminal management DB  609 , the session management DB  610 , the image information DB  611 , and the like. The storage unit  607  may be realized by the HD  404 , the RAM  403  shown in  FIG. 4 , and the like for example. 
     (Function of Relay Apparatus) 
     The relay apparatus  103  may transmit, to one or more communication terminals  102  which participate in the session, data transmitted from another communication terminal  102  which participates in the session. The data may be at least one of the image data, the sound data, and the image information. 
     For example, in  FIG. 1 , a case in which the remote class (an example of the session) may be conducted between the communication terminal  102   a  at the base  105 A, the communication terminal  102   c ,  102   d , and  102   e  at the base  106 C will be described. In this case, the image information input by handwriting into the communication terminal  102   c  is transmitted to the relay apparatus  103 . The relay apparatus  103 , which receives the image information from the communication terminal  102   c , transfers the received image information to the communication terminal  102   a ,  102   d , and  102   e  which participate in the session. 
     Because the present embodiment includes the relay apparatus  103 , in a session held between many communication terminals  102 , each of the communication terminals can communicate by transmitting data via the relay apparatus  103  and does not have to transmit the data directly to another communication terminal  102  which is a communication partner. Thus, the relay apparatus  103  may reduce load of the communication process of the communication terminal  102 . It should be noted that the communication system  100  may have a configuration in which two communication terminals  102  may communicate with each other peer-to-peer without communicating with the relay apparatus  103 . 
     Next, the authentication management DB  608 , the terminal management DB  609 , and the session management DB  610  stored in the storage unit  607  of the communication management system  101  will be described. It should be noted that the image information DB  611  will be described later in a description of a process flow. 
     (Authentication Management DB) 
       FIG. 8A  is a drawing illustrating an example of an authentication management table  801 . In the storage unit  607  of the communication management system  101 , the authentication management DB  608  which includes the authentication management table  801  as shown in  FIG. 8A  may be structured. In the authentication management table  801 , the communication ID of each of the communication terminals  102  is managed in association with the password of each of the communication terminals  102 . The communication ID is the identification information of the communication terminal  102 . 
     It should be noted that the communication ID according to the present embodiment may be an ID which is previously stored in the communication terminal  102  or an ID into which the user input the communication terminal  102 . Alternatively, the communication ID may be identification information recorded in a subscriber identity module (SIM) mounted on the communication terminal  102 . In a case in which the communication ID is the ID which the user inputs into the communication terminal  102 , the communication management system  101  may manage the communication ID which is transmitted from the communication terminal  102  when requiring the login in association with the communication terminal  102  of a login request source. In this way, the communication terminal  102  may be identified based on the communication ID. 
     It should be noted that in the following descriptions, the communication IDs of the communication terminals  102   a ,  102   b , and  102   c  are  10   aa ,  10   ab , and  10   ac , respectively. 
     (Terminal Management DB) 
       FIG. 8B  is a drawing illustrating an example of a terminal management table  802 . In the storage unit  607  of the communication management system  101 , the terminal management DB  609  which includes the terminal management table  802  as shown in  FIG. 8B  may be structured. In the terminal management table  802 , the destination name (terminal name) of the communication terminal  102 , the operational status of the communication terminal  102 , the reception date when the communication management system receives the login request, which will be described later, and the IP address of the communication terminal  102  are managed in association with the communication ID of each of the communication terminals  102 . 
     It should be noted that the operational status indicates online status or offline status. The online status indicates that the communication terminal  102  which corresponds to the communication ID is connected to the communication management system  102 . The offline status indicates that the communication terminal  102  which corresponds to the communication ID is not connected to the communication management system  102 . Further, the online status has “be able to communicate” status in which the communication terminal  102  which corresponds to the communication ID is able to communicate, and “communicating” status in which the communication terminal  102  which corresponds to the communication ID is communicating with one or more communication terminals  102 . 
     (Session Management DB) 
       FIG. 9  is a drawing illustrating an example of a session management table  901 . In the storage unit  607  of the communication management system  101 , the session management DB  610  which includes the session management table  901  as shown in  FIG. 9  may be structured. In the session management table  901 , the starting date, the communication time, the communication ID of the request source, and the communication ID of the destination are managed in association with the corresponding session ID. The session ID is the identification information of the session held in the communication management system  101 . The starting date indicates a date and time when the session, which corresponds to the session ID, has started. The communication time indicates a length of time in which the session, which corresponds to the session ID, has been held. The communication ID of the request source indicates the communication ID of the communication terminal  102  which has requested to start the session, which corresponds to the session ID. The communication ID of the destination indicates one or more communication IDs of the communication terminals  102  which have been designated as the destination (communication partner) by the communication terminal  102 , which has requested to start the session, in the session which corresponds to the session ID. It should be noted that the number of the communication IDs of the destination may be one or more. 
     &lt;Flow of Process&gt; 
     Subsequently, an example of a process of the communication system  100  according to the present embodiment will be described. 
     (Authentication Process) 
       FIG. 10  is a sequence chart illustrating an example of an authentication process according to the present embodiment. The authentication process is a process for establishing the session between the communication management system  101  and each of the communication terminals  102  (referred to as the session sei hereinafter). 
     In step S 1001 , the communication control unit  616  of the communication terminal  102  transmits, to the communication management system  101 , a login request for requesting a login. The process in step S 1001  may be executed, for example, when the power of the communication terminal  102  is turned on, an application which corresponds to the communication system  100  is started in the communication terminal  102 , a predetermined operation is performed on the application or the like. The login request may include, for example, the communication ID of the request source for identifying the communication terminal  102  of the login request source, the password, the IP address of the communication terminal  102  of the request source, and the like. In this way, the transmission/reception unit  601  of the communication management system  101  receives the login request and obtains the information included in the login request. 
     Next, the authentication unit  602  of the communication management system  101  performs authentication of the communication terminal  102  of the login request source in step S 1002  by determining whether a combination of the communication ID and the password included in the received login request is recorded in the authentication management table  801 . Then, in a case in which the authentication unit  602  determines that the communication terminal  102  has authorization according to the authentication (that is, the combination of the communication ID and the password included in the received login request is recorded in the authentication management table  801 ), the status management unit  603  manages (updates) the terminal management table  802  such that the operational status which corresponds to the communication terminal  102  of the login request source becomes online in step S 1003 . 
     Next, the transmission/reception unit  601  of the communication management system  101  transmits, to the communication terminal  102  of the login request source, the authentication result information which indicates that the communication terminal  102  is authenticated in step S 1004 . In this way, the communication control unit  616  of the communication terminal  102  receives the authentication result. Then, in a case in which the authentication unit  602  determines that the communication terminal  102  has the authorization in step S 1002 , the session sei is established between the communication terminal  102  of the login request source and the communication management system  101  in step S 1005 . 
     In the following descriptions, the session between the communication management system  101  and the communication terminal  102  is referred to as “the session sei” and the session between the communication terminals  102  is referred to as “the session sed”. 
     (Establishment Process of Session Between Communication Terminals) 
     Next, a process for establishing the session sed, which is a session for transmitting the content data between the communication terminals  102 , will be described with reference to  FIG. 11 . 
       FIG. 11  is a sequence chart illustrating an example of the establishment process of the session according to the present embodiment. As shown in  FIG. 11 , in response to an event in which the communication terminal  102   a  receives an input operation of destination information by the user (step S 1101 ), the communication control unit  616  transmits, to the communication management system  101 , a request for starting the communication in step S 1102 . The request for starting the communication may include the request source communication ID of the communication terminal  102   a  which requests to start the communication, the destination communication ID of the destination communication terminal  102   b , the IP address of the communication terminal  102   a , and the like. 
     The status management unit  603  of the communication management system  101  which has received the request for starting the communication updates the terminal management DB  609  in step S 1103  based on the request source communication ID of the communication terminal  102   a  which requested to start the communication. For example, the status management unit  603  updates the terminal management table  802  shown in  FIG. 8B  such that the operational status which corresponds to the request source communication ID of the communication terminal  102   a  is changed to “online (communicating)” 
     Next, the session management unit  604  of the communication management system  101  creates a new session ID in step S 1104 . Further, the session information management unit  702  records the created session ID, the request source communication ID of the request source communication terminal  102   a , and the destination communication ID of the destination communication terminal  102   b  in the session management table  901  shown in  FIG. 9  in association with each other in step S 1105 . 
     Subsequently, the session control unit  701  of the communication management system  101  transmits the request for starting the communication to the destination communication terminal  102   b  in step S 1106 . The request for starting the communication may include, for example, the communication ID of the communication terminal  102   a  which has requested to start the communication, the communication ID of the destination terminal  102   b , the IP address of the communication management system  101 , and the like. In this way, the communication control unit  616  of the destination communication terminal  102   b  receives the request for starting the communication. 
     In response to receiving the request, the communication terminal  102   b  may display, on the display unit  614  or the like, information which indicates that the request for starting the communication is received in order to prompt a response operation of the user. Further, in response to an event in which the communication terminal  102   b  receives the response operation by the user in step S 1107 , the communication control unit  616  transmits, to the communication management system  101 , a start response including information which indicates whether the response (start request) is permitted in step S 1108 . The start response may include, for example, the destination communication ID of the destination communication terminal  102   b , the session ID, the information which indicates whether the response is permitted, and the like. In a case in which an input for permitting the communication by the user is received at the communication terminal  102   b  side according to the information which indicates whether the response is permitted, the information indicates that the response is permitted. In a case in which an input for rejecting the communication by the user is received at the communication terminal  102   b  side according to the information which indicates whether the response is permitted, the information indicates that the response is not permitted. In the following, the case in which the communication terminal  102   b  transmits, to the communication management system  101 , the start response including the information which indicates that the response (start request) is permitted will be described. 
     The communication management system  101  receives the start response from the communication terminal  102   b . Further, the status management unit  603  of the communication management system  101  updates the terminal management DB  609  in step  1109  based on the communication ID of the destination communication terminal  102   b  included in the start response. For example, the status management unit  603  may change the operational status which corresponds to the communication ID of the destination communication terminal  102   b  to “online (communicating)” in the terminal management table  802  shown in  FIG. 8B . 
     Further, in response to the start response from the communication terminal  102   b , the session control unit  701  of the communication management system  101  transmits the start response to the request source communication terminal  102   a . The start response may include, for example, the session ID, information which indicates the start of the session, and the like. 
     Subsequently, the session control unit  701  of the communication management system  101  controls the establishment of the session sed in which the image data and the sound data are transmitted between the communication terminal  102   a  and the communication terminal  102   b  via the network  104 . 
     A method for establishing the session sed is not limited particularly. For example, the session control unit  701  may transmit, to the communication terminal  102   a  and the communication terminal  102   b , connection information for connecting to the relay apparatus  103 . For example, the connection information of the relay apparatus  103  may be included in the start request which is transmitted to the communication terminal  102   b  by the session control unit  701  in step S 1106 . Similarly, the connection information of the relay apparatus  103  may be included in the start response transmitted to the communication terminal  102   a  by the session control unit  701  in step S 1110 . 
     Further, the session control unit  701  transmits, to the relay apparatus  103 , a request for starting a relay of the session established between the communication terminal  102   a  and the communication terminal  102   b . In this way, for example, the session sed between the communication terminal  102   b  and the relay apparatus  103 , and the session sed between the communication terminal  102   a  and the relay apparatus  103  may be established in step S 1111  and step S 1112 . 
     According to the above described process, between the request source communication terminal  102   a  and the destination communication terminal  102   b , the transmission and the reception of the image data and the sound data, and the sharing of the image information (stroke information), and the like are started in step S 1113 . 
     (Accumulation Process of the Image Information) 
     Next, a process after the sharing of the image information starts in step S 1113  shown in  FIG. 11  will be described. It should be noted that the relay apparatus  103  is omitted in  FIG. 12  because the relay apparatus  103  only relays (transfers) the data between the communication terminal  102   a  and the communication terminal  102   b.    
       FIG. 12  is a sequence chart illustrating an example of an accumulation process of the image information according to the present embodiment. After the image information is shared in step S 1113  shown in  FIG. 11 , for example, in response to receiving the image information such as the stroke information input by handwriting in step S 1201 , the communication terminal  102   a  outputs the image based on the image information to the display unit  614  in step S 1202 . 
     Further, the communication control unit  616  of the communication terminal  102   a  transmits the received image information to the communication terminal  102   b  with which the communication terminal  102   a  shares the image information in step S 1203 . The image information transmitted at that time may include, for example, the communication ID of the communication terminal  102   a  of the transmission source, the session ID, a seat number, the image information, time information, and the like. It should be noted that, in the present embodiment, the image information is also transmitted to the communication management system  101  in step S 1204 . 
     At that time, the image information transmitted to the communication management system  101  may be, for example, information which is transmitted by the communication control unit  616  of the communication terminal  102   a  to the communication management system  101  using the session sei established between the communication terminal  102   a  and the communication management system  101 . Further, the image information transmitted to the communication management system  101  may be information which is transferred by the relay apparatus  103  to the communication management system  101  after the communication control unit  616  of the communication terminal  102   a  has transmitted the image information to the relay apparatus  103 . 
     The communication terminal  102   b  which has received the image information transmitted from the communication terminal  102   a  outputs the image based on the received image information to the display unit  614  in step S 1205 . On the other hand, the communication management system  101  which has received the image information transmitted from the communication terminal  102   a  records (accumulates) the received image information in the image information DB  611  in step S 1206 . 
     Similarly, for example, in response to receiving the image information such as the stroke information input by handwriting in step S 1207 , the communication terminal  102   b  outputs the image based on the image information to the display unit  614  in step S 1208 . Further, the communication control unit  616  of the communication terminal  102   b  transmits the received image information to the communication terminal  102   a  with which the communication terminal  102   b  shares the image information in step S 1209 . It should be noted that the image information is also transmitted to the communication management system  101  in step S 1210 . 
     At that time, the image information transmitted to the communication management system  101  may be, for example, information which the communication control unit  616  of the communication terminal  102   b  transmits to the communication management system  101  using the session sei between the communication terminal  102   b  and the communication management system  101 . Further, the image information transmitted to the communication management system  101  may be information which is transferred by the relay apparatus  103  to the communication management system  101  after the communication control unit  616  of the communication terminal  102   b  has transmitted the image information to the relay apparatus  103 . 
     The communication terminal  102   a  which has received the image information transmitted from the communication terminal  102   b  outputs the image based on the received image information to the display unit  614  in step S 1211 . On the other hand, the communication management system  101  which has received the image information transmitted from the communication terminal  102   b  records (accumulates) the received image information in the image information DB  611  in step S 1212 . 
     According to the above described process, the pieces of image information output from the communication terminals  102  which share the image information are recorded in the image information DB  611  sequentially by the image information management unit  605  of the communication management system  101 . 
     Here, the image information DB  611  will be described. 
     (Image Information DB) 
     In the storage unit  607  of the communication management system  101 , the image information DB  611  which includes an image information management table  1301  is structured. 
       FIG. 13  is a diagram illustrating an example of the image information management table  1301  according to the present embodiment. The image information management table  1301  is created for each session ID. The session ID is the identification information of the session established between the communication terminals  102 . For example, another image information management table  1301  is added (the information DB 611  is updated) every time a new session between the communication terminals  102  is established. 
     As shown in  FIG. 13 , the image information management table  1301  is divided into a plurality of sections according to sheet numbers. In the image information management table  1301 , for each section the image information, the communication ID of the transmission source communication terminal  102 , and the time when the image information is generated are recorded in association with the image number. 
     The image information may include, for example, stroke information which indicates strokes such as lines and circles, text information which indicates text, and delete information which indicates an image to be deleted. Further, the image information may include coordinate information which indicates positions of the image to be output or to be deleted and information which indicates a size, color, or a font of the image. Further, the image information may include image information of an image to be modified in addition to the above described image information of the image to be added or to be deleted. 
     In the present embodiment, the text is used as examples of the image. The texts may include characters, symbols and the like. The image information sets are recorded in fields of the image information in the image information management table  1301  in order (descending order) of the image number until the end of service (EOS). 
     Further, according to the present embodiment, the communication terminal  102  can output different images in each workspace. The workspaces are switchable by a tab, a thumbnail or the like displayed in the display unit  614 . The above described sheet number is a number for identifying the workspace. It should be noted that an arbitrary wording for indicating the area in which the image is drawn such as a worksheet, a space, a workspace may be used instead of the sheet. 
     According to the above described configuration, for example, the display control unit  615  of the communication terminal  102   a  may superpose the image based on the image information in order to output the image in the display unit  614  every time the image information such as “Line”, “Circle”, and “Text” is generated in response to receiving the note detection signal at the communication terminal  102   a . Further, the display control unit  615  may superpose the image based on the image information in order to output the image in the display unit  614  every time the image information such as “Line”, “Circle”, and “Text” is transmitted from the communication terminal  102   b  which is the communication partner. 
     Further, the display control unit  615  may delete the image which corresponds to the image information “Delete” among the images output in the superposing manner every time the image information “Delete” is generated in response to receiving the deletion detection signal at the communication terminal  102   a.    
     Further, the display control unit  615  may delete the image which corresponds to the image information “Delete” among the images output in the superposing manner every time the image information “Delete” is transmitted from the communication terminal  102   b  which is the communication partner. 
     That is, the image shared between the communication terminals  102  in the course of the communication of the session sed can be added or deleted partly. 
     Further, every time one of the communication terminals  102  transmits the image information, the image information management unit  605  of the communication management system  101  records, in the image information management table  1301  of the image information DB  611 , the transmitted image information, the communication ID, the time and the like. 
     (Restoring Process of the Image Information) 
     For example, the communication system  100  according to the present embodiment, after the session starts or during the session, may restore the image information recorded in the image information DB  611  in order to share the image information between the communication terminals  102  in response to the operation of the communication terminal  102  by the user. In this way, the user of the communication system  100  can easily restart the previous session using the restored image. 
     Specifically, the storage unit  607  can store image information of one or more sessions. The image information includes image information of a first session in which a first communication terminal  102  and a second communication terminal  102  have participated in the past. The storage unit  607  can store the image information of the first session in association with identification information of the first session. When a second session, which differs from the first session, is held between the first communication terminal  102  and the second communication terminal  102 , the image information transmission unit  704  can transmit, to the first communication terminal  102  and the second communication terminal  102 , which participate in the second session, the image information of the first session stored in the storage unit  607 . In this way, the first communication terminal  102  and the second communication terminal  102  can hold the second session using the image information of the first session. 
     Further, when a third session, which differs from the first session, is held between a third communication terminal  102  and a fourth communication terminal  102 , the image information transmission unit  704  can restrict transmission of, to the third communication terminal  102  and the fourth communication terminal  102  which participate in the third session, the image information of the first session stored in the storage unit  607 . It should be noted that the first communication terminal  102  and the second communication terminal  102  do not participate in the third session. 
     Moreover, when a fourth session, which differs from the first session, is held between the third communication terminal  102  and the first communication terminal  102 , the image information transmission unit  704  can restrict transmission of, to the third communication terminal  102  and the first communication terminal  102  which participate in the fourth session, the image information of the first session stored in the storage unit  607 . It should be noted that the second communication terminal  102  and the fourth communication terminal  102  do not participate in the fourth session. 
     Moreover, after the first to fourth sessions have been held and the pieces of image information of the first to fourth sessions have been stored in the storage unit  607 , when a fifth session in which the first communication terminal  102  and the second communication terminal  102  participate is held, the image information transmission unit  704  can transmit, to the first communication terminal  102  and the second communication terminal  102 , the image information of the first session and the second session, because the communication terminals  102  participating in the fifth session match the communication terminals  102  which have participated in the first session and the second session. 
     At that time, the image information transmission unit  704  can restrict the transmission, to the first communication terminal  102  and the second communication terminal  102 , of the image information of the third session and the image information of the fourth session, because the communication terminals  102  participating in the fifth session do not match the communication terminals  102  which have participated in the third session and the fourth session. 
     As described above, the present embodiment can select, from the image information of one or more sessions stored in the storage unit  607 , image information to be transmitted in accordance with the communication terminals  102  which participate in a session to be held. 
       FIG. 14  is a sequence chart illustrating an example of a restoring process of the image information according to the present embodiment. The communication management system  101 , for example, may start the restoring process of the image information at an arbitrary timing, after the image information has been shared between the communication terminal  102   a  and the communication terminal  102   b  in step S 1113  according to the establishment process of the session shown in  FIG. 11 . 
     For example, as shown in  FIG. 14 , in response to an event in which the communication terminal  102   a  receives a restoring operation from the user in step S 1401 , the communication control unit  616  of the communication terminal  102   a  transmits an image information request to the communication management system  101  in step S 1402 . The image information request may include, for example, the communication ID of the request source communication terminal  102   a , the communication ID of the destination communication terminal  102   b , the session ID of the session currently being held, and the like. 
     In step S 1403 , the obtain control unit  703  of the communication management system  101 , which has received the image information request from the communication terminal  102   a , obtains the session information (session management table  901 , for example) from the session management DB  610 . The obtain control unit  703 , which has obtained the session information, can specify one or more sessions in which the communication terminal  102   a  and the communication terminal  102   b  participated in the past based on the communication ID of the communication terminal  102   a  and the communication ID of the communication terminal  102   b  included in the image information request. 
     In step S 1404 , the obtain control unit  703  creates history of the image information with regard to the one or more sessions held in the past between the communication terminal  102   a  and the communication terminal  102   b . For example, the obtain control unit  703  obtains (extracts) information of the one or more sessions in which the communication terminal  102   a  and the communication terminal  102   b  participated among the sessions whose image information sets are recorded in the image information DB  611 . In this way, among the sessions held between the communication terminal  102   a  and the communication terminal  102   b  in the past, a list (history) of the image information recorded in the image information DB  611  is created. 
     In step S 1405 , the obtain control unit  703  transmits the created history of the image information (the information of the one or more sessions in which the communication terminal  102   a  and the communication terminal  102   b  participated among the sessions whose image information sets are recorded in the image information DB  611 ) to the communication terminal  102   a.    
     In step S 1406 , the display control unit  615  of the communication terminal  102   a , which has received the history of the image information from the communication management system  101 , causes the display unit  614  to display a selecting screen of the history image information in order to prompt the user to select the image information to be restored. For example, the display control unit  615  causes the display unit  614  to display the information of the one or more sessions received from the communication management system  101  in a selectable manner.  FIG. 15  shows a screen example which is displayed in the display unit  614  of the communication terminal  102   a  at that time. 
       FIG. 15  is an example of a selecting screen  1501  of the history of the image information according to the present embodiment. In the example shown in  FIG. 15 , the selecting screen  1501  of the history of the image information is displayed in the display unit  614  of the communication terminal  102  (the communication terminal  102   a ). In the selecting screen  1501  of the history of the image information, selecting buttons  1502  are displayed in a selectable manner. The selecting buttons are buttons for selecting, among the sessions whose image information are recorded in the image information DB  611 , the one or more sessions in which the communication terminal  102   a  and the communication terminal  102   b  participated. 
     The user of the communication terminal  102  may select, for example, one of the selecting buttons  1502  which indicates (include) the time and date of the remote class of the previous time from the selecting screen  1501  of the history of the image information displayed in the display unit  614  using the input unit  511  of the communication terminal  102  or the like. 
     For example, in a case in which the communication terminal  102  is a shared communication terminal  102  and many users use the shared communication terminal  102  for various sessions, it may be difficult to select, from histories of the various sessions, a necessary session such as the history of the remote class of the previous time. However, the communication system  100  according to the present embodiment can display in the selectable manner, based on the communication ID of the communication terminal  102   a  and the communication ID of the communication terminal  102   b  which are participating in the current session, the information of the one or more sessions held in the past by the same combination of the communication terminals  102  (held by the communication terminal  102   a  and the communication terminal  102   b ). In this way, the user of the communication terminal  102   a  can easily select the history of the previous session. 
     It is preferable that the selecting buttons  1502  displayed in the selecting screen  1501  include information which indicates the time and date of the session whose image information is recorded. The user of the communication terminal  102   a  can easily confirm, for example, the time and date when the previous remote class was held. Thus the user can easily restore the image information of the previous remote class. Further, for example, because the information which indicates the time and date of the session whose image information is recorded can be obtained easily from the session management table  901  shown in  FIG. 9 , the user can obtain the image information of the previous remote class without inputting the session name, the session ID, or the like. 
     The description of the sequence chart shown in  FIG. 14  will be started again. 
     In response to an event in which the operation input reception unit  613  of the communication terminal  102   a  receives the selecting operation of the user from the selecting buttons  1502  shown in  FIG. 15  or the like in step S 1407 , the communication control unit  616  transmits, to the communication management system  101 , the information which indicates the selected history in step S 1408 . For example, among the pieces of information of the one or more sessions displayed in the display unit  614 , the communication control unit  616  may transmit, to the communication management system  101 , information which designates one session selected by the user. 
     The obtain control unit  703  of the communication management system  101 , which has received the information which indicates the selected history from the communication terminal  102   a , obtains the image information which corresponds to the selected history (session) from the image information DB  611  in step S 1409 . For example, based on the information which has been received from the communication terminal  102   a  and designates the one session selected by the user, the obtain control unit  703  determines the image information of the session to be obtained from the image information DB  611 , and obtains the image information. 
     In step S 1410 , the image information transmission unit  704  of the communication management system  101  transmits the image information obtained by the obtain control unit  703  to the communication terminal  102  which participates in the current session. For example, the image information transmission unit  704  transmits the obtained image information to the communication terminal  102   a  which has transmitted the image information request. 
     In step S 1411 , the display control unit  615  of the communication terminal  102   a , which has received the image information from the communication management system  101 , restores the image information of the session selected in step S 1407  in order to cause the display unit  614  to display the image information based on the received image information. 
     In step S 1412 , the communication terminal  102   a  shares the restored image information with the communication terminal  102   b  with which the image information is shared. In this way, the image displayed in the display unit  614  of the communication terminal  102   a  is also displayed in the communication terminal  102   b.    
     According to the above described process, for example, from the plurality of sessions performed in the past between the communication terminal  102   a  and the communication terminal  102   b , the user of the communication terminal  102   a  may easily restore the images of the previous session selectively. 
     It should be noted that the process shown in  FIG. 14  is a preferable example of the restoring process of the image information according to the present embodiment. For example, in steps S 1404  to S 1409  shown in  FIG. 14 , among the sessions whose image information sets are recorded in the image information DB  611 , the obtain control unit  703  may obtain the image information of the latest session in which the communication terminal  102   a  and the communication terminal  102   b  have participated. Further, in step S 1404 , in a case in which the number of sessions in which the communication terminal  102   a  and the communication terminal  102   b  have participated is one among the sessions whose image information sets are stored in the image information DB  611 , the process in step S 1405  to S 1408  may be omitted. 
     In the following, an example of a displaying screen displayed in the communication terminal  102   a  according to the above described process will be described. 
       FIG. 16  is a drawing illustrating an example of the displaying screen displayed in the communication terminal  102   a  according to the present embodiment.  FIG. 16  shows an example of the displaying screen displayed in the communication terminal  102   a  after the image information has been restored in step S 1411  in  FIG. 14 . In the example shown in  FIG. 16 , restored image information  1601  is displayed in the display unit  510  of the communication terminal  102   a . The restored image information  1601  may be, for example, image information recorded when the previous remote class was conducted. The user of the communication terminal  102   a  may, for example, restart and continue the previous remote class using the restored image information  1601 . 
     In  FIG. 16 , a thumbnail “ 1 ”  1602  shown under the restored image information  1601 , for example, may correspond to the sheet number of the image information management table  1301  shown in  FIG. 13 . For example, when the thumbnail “ 1 ”  1602  is selected in  FIG. 16 , the image information of the sheet number  1  is displayed in the display unit  510  as the restored image information  1601 . Similarly, when a thumbnail “ 2 ”  1603  is selected in  FIG. 16 , the image information of the sheet number  2  is displayed in the display unit  510  as the restored image information  1601 . 
     Further, in the example shown in  FIG. 16 , a projected image  1604  at the base of the communication terminal  102   b  side and a projected image  1605  at the base of the communication terminal  102   a  side are displayed in the display unit  510  of the communication terminal  102   a . In this way, the participants of the session may establish the session such as the remote class, the remote conference, and the like using the projected image, the sound of other participants, and the shared image displayed in the display unit  510 . 
     (Process after the Image Information is Restored) 
       FIG. 17  is a sequence chart illustrating an example of a process after the image information is restored according to the present embodiment. Further, an example of a process in a case in which three or more communication terminals  102  share the image information will be described together with reference to  FIG. 17 . 
     Before the process starts in  FIG. 17 , the communication terminals  102   a ,  102   b , and  102   c  may, for example, execute the authentication process shown in  FIG. 10  and the establishment process of the session shown in  FIG. 11  and share the image information with each other. 
     In step S 1701  shown in  FIG. 17 , the communication terminal  102   a  may restore the image information according to the restoring process shown in  FIG. 14 . In response to restoring the image information, the display control unit  615  of the communication terminal  102   a  outputs the image based on the restored image information to the display unit  614  in step S 1702 . 
     Further, the communication control unit  616  of the communication terminal  102   a  transmits the restored image information to the relay apparatus  103  in step S 1703  using the session sed. At that time, the restored image information transmitted to the relay apparatus  103  includes the current session ID. 
     The relay apparatus  103 , which has received the restored image information form the communication terminal  102   a , transfers the received image information to the other communication terminals  102   b  and  102   c  which participate in the session in step S 1704  and step S 1705  based on the session ID included in the received information. 
     The display control units  615  of the communication terminals  102   b  and  102   c , which have received the restored image information from the relay apparatus  103 , cause the corresponding display units  614  to display the image in step S 1706  and step S 1707 , respectively, based on the received and restored image information. 
     As described above, the communication system  100  according to the present embodiment can easily restore and share the image information of the previous session if three or more communication terminals  102 , which share the image information, participate the session. 
     Further, in step S 1707 , the communication control unit  616  of the communication terminal  102   a  according to the present embodiment may transmit, to the communication management system  101 , the information similar to the restored image information transmitted in step S 1703 , using the session sei, for example. At that time, the restored image information transmitted to the communication management system  101  may include the current session ID and the like. 
     The image information management unit  605  of the communication management system  101 , which has received the restored image information from the communication terminal  102   a , records the restored information in the image information DB  611  as the image information of the current session in step S 1709 . 
     Next, in response to an event in which the communication terminal  102   a  receives an input operation of new image information with respect to the image displayed in the display unit  614  in step S 1710 , the display control unit  615  displays the image, which is input, on the image being displayed in a superimposing manner in step S 1711 . Further, the communication control unit  616  of the communication terminal  102   a  transmits the image, which is input, to the relay apparatus  103  in step S 1712  using the session sed. 
     The relay apparatus  103 , which has received the input image information, transfers the received image information to the other communication terminals  102   b  and  102   c  which participate in the session in step S 1713  and step S 1714 , respectively, based on the session ID included in the received information. 
     The display control units  615  of the communication terminals  102   b  and  102   c , which have received the input image information from the relay apparatus  103 , cause the corresponding display unit  614  to display the image in step S 1715  and step S 1716 , respectively, based on the received input image information. 
     Further, the communication control unit  616  of the communication terminal  102   a  may transmit, to the communication management system  101 , the information similar to the restored image information, which has been transmitted in step S 1703 , in step S 1717  using the session sei, for example. 
     The image information management unit  605  of the communication management system  101 , which has received the input image information from the communication terminal  102   a , records the input information in the image information DB  611  as the image information of the current session in step S 1718 . 
     As described above, the communication system  100  according to the present embodiment can restore the image, which has been input in the previous session, in order to input and manage the new image information with respect to the restored image. 
     (Another System Configuration) 
     In the above, the system configuration of the communication system  100  shown in  FIG. 1  is described. However, the system configuration shown in  FIG. 1  is an example, and the present invention is not limited to this. In the following, another configuration example of the communication system  100  according to the present invention will be described briefly. 
       FIG. 18  is a drawing illustrating another configuration example of the communication system  100  according to the embodiment. As shown in  FIG. 18 , the communication system  100  includes a plurality of communication terminals  102   aa  to  102   dc , a plurality of relay apparatuses ( 103   a ,  103   b ,  103   c , and  103   d ), a communication management system  101 , and a program supply system  90 . 
     It should be noted that an arbitrary communication terminal of the communication terminals  102   aa  to  102   dc  is referred to as the communication terminal  102 ″. Similarly, an arbitrary relay apparatus of the relay apparatuses ( 103   a ,  103   b ,  103   c , and  103   d ) is referred to as the relay apparatus  103 ″. 
     The user of each of the communication terminals  102  may perform the session such as the remote class and the TV conference with another user of the communication terminal  102  using images and sound transmitted and received in real time. Further, the communication terminals  102  may share the image information such as a character, a figure, and a symbol which are input by handwriting. The relay apparatus  103  relays the content data between the communication terminals  102 . The communication management system  101  manages the communication terminals  102  and the relay apparatuses  103  in an integrated fashion. 
     A plurality of routers ( 70   a  to  70   d ,  70   ab ,  70   cd ) shown in  FIG. 18  select the optimum path for the image data and the sound data. In this example, an arbitrary router of the routers ( 70   a  to  70   d ,  70   ab ,  70   cd ) may be referred to as the router  70 ″. The program supply system  90  includes a storage means (unit) in which a communication apparatus program for causing the communication terminals  102  to realize various kinds of functions or various kinds of means is stored. The program supply system  90  can transmit the communication apparatus program to the communication terminals  102 . 
     The storage means of the program supply system  90  stores a relay apparatus program for causing the relay apparatus  103  to realize various kinds of functions or various kinds of means. The program supply system  90  can transmit the relay apparatus program to the relay apparatus  103 . Further, the storage means of the program supply system  90  stores a communication management program for causing the communication management system  101  to realize various kinds of functions or various kinds of means. The program supply system  90  can transmit the communication management program to the communication management system  101 . 
     The communication terminals ( 102   aa ,  102   ab ,  102   ac ), the relay apparatus  103   a , and the router  70   a  are connected via a LAN  2   a  in a communicable manner (be able to communicate with each other). The communication terminals ( 102   ba ,  102   bb ,  102   bc ), the relay apparatus  103   b , and the router  70   b  are connected via a LAN  2   b  in a communicable manner. Further, the LAN  2   a  and the LAN  2   b  are connected via a private line tab including a router  70   ab  in a communicable manner, and are structured (located) within a predetermined area A. For example, the area A is Japan, and the LAN  2   a  is structured in an office in Tokyo, and the LAN  2   b  is structured in an office in Osaka. 
     On the other hand, the communication terminals ( 102   ca ,  102   cb ,  102   cc ), the relay apparatus  103   c , and the router  70   c  are connected via a LAN  2   c  in a communicable manner. The communication terminals ( 102   da ,  102   db ,  102   dc ), the relay apparatus  103   d , and the router  70   d  are connected via the LAN  2   d  in a communicable manner. The LAN  2   c  and LAN  2   d  are connected via a private line  2   cd  including a router  70   cd  in a communicable manner, and are structured within a predetermined area B. For example, the area B is America, and the LAN  2   c  is structured (located) in an office in New York, and the LAN  2   d  is structured in an office in Washington D.C. The area A and the area B are connected via the routers ( 70   ab ,  70   cd ) to the Internet  2   i  in a communicable manner. 
     Further, the communication management system  101  and the program supply system  90  are connected via the Internet  2   i  to the communication terminals  102  and the relay apparatuses  103  in a communicable manner. The communication management system  101  and the program supply system  90  may be installed in the area A or the area B, or may be installed in an area other than the area A and the area B. 
     It should be noted that in the example shown in  FIG. 18 , the communication network  2  is structured to include the LAN  2   a , the LAN  2   b , the private line tab, the Internet  2   i , the private line  2   cd , the LAN  2   c , and the LAN  2   d.    
     As described above, the communication system  100  according to the present embodiment may increase the number of the communication terminals  102  or the network  104  in order to hold the session in various countries, areas, offices or the like and to restart the session easily. 
     &lt;Supplement to Embodiment&gt; 
     Each program for the communication terminal  102  and the communication management system  101  may be provided (distributed) on a recording medium which can be read out by the computer such as the recording medium  306  and the recording medium  406 . The recording medium may have an installable file form or an executable file form. Further, an optical disk such as a Compact Disc Recordable (CD-R), a Digital Versatile Disk (DVD), and a blue-ray disc may be used for the recording medium. Further, the above described recording medium, the HD  404 , the storage unit  504 , or the like which stores the program may be provided to a domestic or overseas as a program product. 
     Further, the communication terminal  102  and the communication management system  101  according to the above described embodiments may be configured with a computer or may be configured with plural computers to which arbitrarily divided parts (functions or means) are assigned, respectively. 
     Moreover, although an image sharing apparatus (intermediate concept) such as the communication terminal  102  (subordinate concept) is used for performing the session such as the remote class and the remote conference, the present invention is not limited to this. The present invention may be used in a field of communication including the TV conference or the like as a broad concept. For example, a projector system, digital signage, a text sharing system, a car navigation system, a communication system for game machines or the like may be used for the embodiment. 
     Further, the present invention is not limited to these embodiments, but various variations and modifications may be made without departing from the scope of the present invention. 
     The present application is based on and claims the benefit of priority of Japanese Priority Application No. 2015-028808 filed on Feb. 17, 2015, with the Japanese Patent Office, the entire contents of which are hereby incorporated by reference.