Abstract:
Provided is an information management method for use in an information management system that includes a coordinate pointing device for identifying a paper medium, and a contents server for managing a digital document, and holds an attribute of the digital document and an attribute of a paper document obtained by printing the digital document on the paper medium, the information management method comprising: judging whether a paper document identified by the coordinate pointing device is a master of a document by referring to an attribute of the paper document; and permitting, when it is judged that the identified paper document is the master of the document, to update information annotated to the identified paper document in a digital document corresponding to the paper document to which the information has been annotated

Description:
CLAIM OF PRIORITY 
       [0001]    The present application claims priority from Japanese patent application 2006-103041 filed on Apr. 4, 2006, the content of which is hereby incorporated by reference into this application. 
       BACKGROUND OF THE INVENTION 
       [0002]    This invention relates to an information management system for managing a document or the like, and more particularly, to a technology for managing a paper document and a digital document. 
         [0003]    In recent years, as a result of advancement of a digital technology, it has become possible to digitize hand-written information annotated to paper with ease. However, currently, a computer manages only a digital document obtained by digitizing a paper document. Under this condition, hand-written information annotated to the paper document is not managed digitally, which makes it impossible to effectively use the hand-written information. 
         [0004]    As a technology for solving this problem, there is proposed a hybrid document management system which can manage hand-written information. This hybrid document management system manages a document containing hand-written information without distinguishing between a paper document and a digital document. 
         [0005]    Also, a pen-type input device (digital pen) that digitally obtains a path of a pen tip is put to practical use. The digital pen inputs the obtained pen tip path into a computer. Examples of the digital pen include the “Anoto pen” developed by Anoto AB in Sweden. The details of the digital pen are described in WO 01/71473 A1. The digital pen has an advantage that it is possible even for a user, who is not used to using a keyboard or a mouse, to use the pen easily, and is therefore expected to be applied to application tasks in the electronic government and other fields. 
       SUMMARY OF THE INVENTION 
       [0006]    With the related technology described above, the paper document and the digital document have not been managed appropriately. It has been difficult to manage which of the paper document and the digital document should be dealt with as a master of the document and whether changes to the documents should be permitted. In other words, when the paper document is set as a master of the document, it is required that only a change to the paper document can be reflected in the digital document and a change to the digital document is restrained. In contrast, when the digital document is set as a master of the document, it is required that only a change to the digital document can be reflected in the paper document and a change to the paper document is restrained. 
         [0007]    In addition, it is required to inform a user whether a document, to which he/she is attempting to make a change, is a master of the document and whether consistency with the latest version of the digital document is maintained. In other words, it is required to make it possible to confirm, at a computer, whether the paper document held by the user is a master of the document and whether the paper document is a document obtained by printing the latest version of the digital document. 
         [0008]    A representative aspect of this invention is as follows. That is, there is provided an information management method for use in an information management system that includes a coordinate pointing device for identifying a paper medium, and a contents server for managing a digital document, and holds an attribute of the digital document and an attribute of a paper document obtained by printing the digital document on the paper medium, the information management method comprising: judging whether a paper document identified by the coordinate pointing device is a master of a document by referring to an attribute of the paper document; and permitting, when it is judged that the identified paper document is the master of the document, to update information annotated to the identified paper document in a digital document corresponding to the paper document to which the information has been annotated. 
         [0009]    According to an aspect of this invention, it becomes possible to manage a paper document and a digital document as appropriate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present invention can be appreciated by the description which follows in conjunction with the following figures, wherein: 
           [0011]      FIG. 1  is a block diagram of a document management system according to the embodiment of this invention; 
           [0012]      FIG. 2  is a block diagram of the contents server according to the embodiment of this invention; 
           [0013]      FIG. 3  is a block diagram of the client terminal according to the embodiment of this invention; 
           [0014]      FIG. 4  is a block diagram of the document discarding unit according to the embodiment of this invention; 
           [0015]      FIG. 5  is a diagram of configuration of the digital document information stored in the contents server according to the embodiment of this invention; 
           [0016]      FIG. 6  is a diagram of configuration of the paper document information stored in the contents server according to the embodiment of this invention; 
           [0017]      FIG. 7  is an explanatory diagram of the master flag included in the paper document information according to the embodiment of this invention; 
           [0018]      FIG. 8  is an explanatory diagram of obtainment of relative coordinates on paper by the digital pen according to the embodiment of this invention; 
           [0019]      FIG. 9  is an explanatory diagram showing an example of a stroke set according to the embodiment of this invention; 
           [0020]      FIG. 10  is a diagram of configuration of the stroke set information stored in the contents server according to the embodiment of this invention; 
           [0021]      FIG. 11  is a diagram of configuration of the stroke coordinate information stored in the contents server according to the embodiment of this invention; 
           [0022]      FIG. 12  is a diagram of configuration of the user information stored in the contents server according to the embodiment of this invention; 
           [0023]      FIG. 13  is a flowchart of digital document update according to the embodiment of this invention; 
           [0024]      FIG. 14  is a flowchart of paper document print processing according to the embodiment of this invention; 
           [0025]      FIG. 15  is a flowchart of processing at the time of writing to a paper document according to the embodiment of this invention; 
           [0026]      FIG. 16  is a flowchart of digital document update processing according to the embodiment of this invention; 
           [0027]      FIG. 17  is a flowchart of paper document discarding processing according to the embodiment of this invention; 
           [0028]      FIG. 18  is an explanatory diagram of a meeting attendance table according to the embodiment of this invention; 
           [0029]      FIG. 19  is an explanatory diagram showing an example of a user interface; 
           [0030]      FIG. 20  is an explanatory diagram showing an example of a user interface; 
           [0031]      FIG. 21  is an explanatory diagram showing an example of a user interface; 
           [0032]      FIG. 22  is an explanatory diagram showing an example of a user interface; 
           [0033]      FIG. 23  is an explanatory diagram showing an example of a user interface; 
           [0034]      FIG. 24  is an explanatory diagram showing an example of a user interface; and 
           [0035]      FIG. 25  is an explanatory diagram showing an example of a user interface. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0036]    Next, an embodiment of this invention will be described with reference to the accompanying drawings. 
         [0037]      FIG. 1  is a block diagram of a document management system according to the embodiment of this invention. 
         [0038]    The document management system comprises a contents server  11 A, a contents database  11 B, client terminals  12 , digital pen interfaces  13 , a document discarding unit  15 , a network  17 , and a location information server  19 . 
         [0039]    The contents server  11 A, the client terminals  12 , the document discarding unit  15 , and the location information server  19  are connected to one another through the network  17 . The client terminals  12  and the digital pen interfaces  13  are connected in a wired manner using a universal serial bus (USB) protocol or the like. Alternatively, the client terminals  12  and the digital pen interfaces  13  may be connected in a wireless manner based on Bluetooth, a wireless LAN, a mobile telephone system, infrared rays, or the like. 
         [0040]    The contents server  11 A manages contents and transmits requested contents to the client terminals  12 . The contents server  11 A is connected to the contents database  11 B. The contents database  11 B stores digital documents. 
         [0041]    Each client terminal  12  is a computer device used by a person and transfers information received from the digital pen interface  13  to the contents server  11 A. To the client terminal  12 , a printer is connected. 
         [0042]    Also, the client terminal  12  displays contents (digital document) received from the contents server  11 A and creates a paper document by printing the received digital document using the printer. 
         [0043]    To the digital pen interface  13 , a digital pen  14  is connected. Like in the case of an ordinary pen, with the digital pen  14 , it is possible to annotate characters, figures, and the like to a paper medium. Also, the digital pen  14  comprises a micro-camera at its tip end and shoots image of a dot patter printed on the paper. Further, the digital pen  14  holds a pen ID set in advance. The digital pen  14  comprises a communication interface for connection with the digital pen interface  13  in a wired or wireless manner. 
         [0044]    For instance, as shown in  FIG. 8 , the digital pen  14  obtains dot pattern information printed on a document. It is possible to compute coordinates in a dot pattern space from the dot pattern information. Also, it is possible to identify coordinates on the paper from the dot pattern information obtained by the digital pen  14  by referring to the location information server  19 . 
         [0045]    It should be noted here that it is also possible for the digital pen  14  to transmit, through a mobile telephone system or a wireless LAN system, the identified absolute coordinates, a time at which the dot pattern has been obtained, and the pen ID directly to the contents server  11 A not through the client terminal  12 . 
         [0046]    The document discarding unit  15  is a unit, such as a shredder, which discards paper documents after placing the documents in an unusable state. In particular, the document discarding unit  15  according to this invention has a function of identifying paper documents to be discarded. 
         [0047]    The location information server  19  is a computer device including a CPU, a memory, a storage device, holds a database on which the absolute coordinates in the dot pattern space computed by the digital pen  14  and the relative coordinates on the paper are associated with each other, and provides the relative coordinates on the paper based on the dot pattern on the paper. 
         [0048]      FIG. 2  is a block diagram of the contents server  11 A according to the embodiment of this invention. 
         [0049]    The contents server  11 A comprises a CPU  111 , a memory  112 , a storage unit  113 , and a data communication unit  118 . 
         [0050]    The CPU  111  performs various kinds of processing by invoking and executing various programs stored in the storage unit  113 . The memory  112  includes a work area in which data used by the CPU  111  in the various kinds of processing is stored temporarily. 
         [0051]    The storage unit  113  is constructed by a nonvolatile storage medium (magnetic disk drive, for instance) and stores a document management program  115 , a pen data management program  116 , and a user management program  117 . Those programs are loaded into the memory  112  and then are executed by the CPU  111 , thereby performing the various kinds of processing. 
         [0052]    Also, the storage unit  113  stores digital document information  21  (see  FIG. 5 ), paper document information  22  (see  FIG. 6 ), stroke information  23 , and user information  27  ( FIG. 12 ). The stroke information  23  includes stroke set information  24  ( FIG. 10 ) and stroke coordinate information  25  ( FIG. 11 ). 
         [0053]    The document management program  115  manages the digital document information  21  and the paper document information  22 . The pen data management program  116  manages the stroke information  23 . The user management program  117  manages the user information  27 . 
         [0054]    The data communication unit  118  includes a network interface and a data interface. The network interface is a LAN card that is capable of performing communication using a TCP/IP protocol, for instance. The contents server  11 A is capable of communicating with a device connected to the network  17 , such as the client terminal  12 , through the network interface. The data interface is an interface that is capable of transmitting and receiving data using a SCSI protocol, for instance. The contents server  11 A is capable of reading and writing data from and into the contents database  11 B (more precisely, an external storage device that stores the contents database) through the data interface. 
         [0055]      FIG. 3  is a block diagram of the client terminal  12  according to the embodiment of this invention. 
         [0056]    The client terminal  12  comprises a CPU  121 , a memory  122 , a pen data input unit  123 , an operation input unit  124 , a data display unit  125 , and a data communication unit  126 . 
         [0057]    The CPU  121  reads and executes various programs stored in a storage device (not shown), thereby performing various kinds of processing. The memory  122  includes a work area in which data used by the CPU  121  in the various kinds of processing is stored temporarily. Also, the memory  122  temporarily stores data sent from the contents server  11 A and the digital pen  14 . 
         [0058]    The pen input unit  123  is connected with the digital pen interface  13  in a wired manner (using a USB protocol, for instance) or a wireless manner (based on Bluetooth or a wireless LAN, for instance) and collects information about coordinates and the like obtained by the digital pen  14 . 
         [0059]    The operation input unit  124  is a keyboard, for instance, and is used by a user to input information. The data display unit  125  is constructed using a liquid crystal display, for instance, and displays contents such as a document obtained from the contents server  11 A. 
         [0060]    The data communication unit  126  is a network interface such as a LAN card that is capable of performing communication using a TCP/IP protocol. With this construction, it becomes possible for the client terminal  12  to communicate with the contents server  11 A through the network  17 . 
         [0061]    It should be noted here that the pen input unit  123  and the data communication unit  126  may be the same interface. 
         [0062]      FIG. 4  is a block diagram of the document discarding unit  15  according to the embodiment of this invention. 
         [0063]    The document discarding unit  15  comprises a CPU  151 , a memory  152 , a paper discriminating unit  153 , an operation input unit  154 , a data display unit  155 , a data communication unit  156 , and a document shredding unit  157 . 
         [0064]    The CPU  151  reads and executes various programs stored in a storage device (not shown), thereby performing various kinds of processing. The memory  152  includes a work area in which data used by the CPU  151  in the various kinds of processing is stored temporarily. 
         [0065]    The paper discriminating unit  153  comprises a camera that photographs an image of paper in order to identify a paper document to be discarded. The CPU  151  identifies a document thrown in for discarding using an image photographed by the paper discriminating unit  153 . Then, the CPU  151  judges whether it is possible to discard the thrown-in document. 
         [0066]    The operation input unit  154  is a keyboard, for instance, and is used by a user to input information. The data display unit  155  is constructed using a liquid crystal display, for instance, and displays information about the document to be discarded. 
         [0067]    The data communication unit  156  is a network interface such as a LAN card that is capable of performing communication using a TCP/IP protocol. With this construction, it becomes possible for the document discarding unit  15  to communicate with the contents server  11 A through the network  17 . 
         [0068]      FIG. 5  is a diagram of configuration of the digital document information  21  stored in the contents server  11 A according to the embodiment of this invention. 
         [0069]    The digital document information  21  contains, for each digital document, a digital file  210 , a document ID  211 , an owner user ID  212 , a creation date and time  213 A, an update date and time  213 B, an access date and time  213 C, a size  214 , a corresponding application  215 , a pointer to the digital document  216 , digital document access rights  217 , a number of print paper objects  218 A, paper object IDs  218 B, and a digital/paper correspondence table  219 . 
         [0070]    The digital file  210  is a file name of the digital document. The document ID  211  is a unique identifier of the digital document. The owner user ID  212  is a unique identifier of a user who owns the digital document. 
         [0071]    The creation date and time  213 A is a creation date and time of the digital document. The update date and time  213 B is the last update date and time of the digital document. The access date and time  213 C is the last reading/writing date and time of the digital document. 
         [0072]    The size  214  is a storage capacity that is necessary to store the digital document. The corresponding application  215  is the name of application software that is necessary to access the digital document. It should be noted that the application software used to read the digital document and the application software used to update the digital document may be different from each other. In this case, in the corresponding application field  215 , multiple application software names are recorded. 
         [0073]    The pointer to the digital document  216  is a location on a disk at which the digital document is stored. Through a path recorded as the pointer to the digital document  216 , it is possible to access a corresponding digital file. The digital document access rights  217  are rights to access the digital document. For instance, information about a range of users, who are capable of viewing, updating, or accessing the digital document, is recorded. 
         [0074]    The number of print paper objects  218 A is the number of paper documents generated based on the digital document. The number of the recorded paper object IDs  218 B is equal to the number of print paper objects  218 A. Each paper object ID  218 B is a unique identifier of a paper document generated from the digital document and is a link to the paper document information  22  ( FIG. 6 ). 
         [0075]    When a paper document is generated by printing the digital document, a new record of the paper document information  22  is created, the number of print paper objects  218 A is incremented, and a paper object ID of the created paper document information  22  is recorded. On the other hand, when the paper document information  22  is erased at the time of discarding a paper document, the number of print paper objects  218 A is decremented and a corresponding paper object ID  218 B is erased. 
         [0076]    The digital/paper correspondence table  219  shows whether the digital document is a master of a document. In other words, when the digital document is a master of the document (when no paper document is a master of the document), “master” is recorded. On the other hand, when a paper document generated through printing is set as a master of the document, the digital document becomes a non-master of the document and the digital/paper correspondence table  219  is changed to “locked”. 
         [0077]    The construction of the digital document information  21  described above is an example and it is sufficient that the digital document information  21  holds information showing whether the digital document is a master of the document and the held information is updated. In other words, it is sufficient that the digital document information  21  contains at least the digital file  210 , the document ID  211 , the paper object IDs  218 B, and the digital/paper correspondence table  219 . 
         [0078]      FIG. 6  is a diagram of configuration of the paper document information  22  stored in the contents server  11 A according to the embodiment of this invention. 
         [0079]    The paper document information  22  contains, for each paper document, a paper object ID  220 , a dot pattern ID  221 , an owner user ID  222 , a master flag  223 , a print time digital file  224 A, a print date and time  224 B, a print person ID  224 C, the last update date and time  225 , a document size  226 , a document security level  227 , a number of stroke sets  228 A, and stroke set IDs  228 B. 
         [0080]    The paper object ID  220  is a unique identifier of the paper document. It should be noted that even in the case of paper documents having the same information, when owned by different owners, the paper documents become different paper documents, so different paper object IDs  220  are assigned and different records of the paper document information  22  are generated. Ordinarily, paper documents printed by different users are printed along with different dot patterns. 
         [0081]    The dot pattern ID  221  is an identifier of a dot pattern printed on the paper document. It should be noted that the paper document may be generated by printing information of the digital document on blank paper on which a dot pattern determined in advance has been printed. 
         [0082]    The owner user ID  222  is a unique identifier of a user who owns the paper document. The master flag  223  indicates whether the paper document is a master of the document. As shown in  FIG. 7 , as the value of the master flag, there are four kinds of values. 
         [0083]    The print time digital file  224 A is a file name of digital data from which the paper document has been printed. The print date and time  224 B is a print date and time of the paper document. The print person ID  224 C is a unique identifier of a person who has printed the paper document. The print person ID  224 C is the same as the owner user ID  222  in ordinary cases but there is also a case where the print person ID  224 C is different from the owner user ID  222 . 
         [0084]    The last update date and time  225  is the last update date and time of the paper document through handwriting of a memo or the like on the paper document, for instance. The document size  226  shows the size of paper suited for printing of the paper document and a coordinate of a left upper corner of an area thereof and a coordinate of a right lower corner are stored. In the case shown in the drawing, the document size  226  is expressed in units of millimeter by setting the left upper corner as an origin. 
         [0085]    The document security level  227  is a confidence level of the paper document. By the document security level  227 , it is determined whether each user is capable of viewing the paper document and whether the user is capable of printing the document. 
         [0086]    The number of stroke sets  228 A is the number of stroke sets written on the paper document with the digital pen  14 . The number of the recorded stroke set IDs  228 B is equal to the number of stroke sets  228 A. 
         [0087]    Each stroke set is a collection of mutually related lines (strokes) and is obtained using layout analysis in character recognition, for instance. In the layout analysis, the mutually related lines are identified based on times, at which the lines have been annotated, and/or location relations among the lines, thereby obtaining the stroke set. In other words, strokes annotated at near times and near locations constitute one stroke set. 
         [0088]    Each stroke set ID  228 B is a unique identifier of a stroke set written on the paper document and is a link to the stroke set information  24  ( FIG. 10 ). 
         [0089]    The construction of the paper document information  22  described above is an example and it is sufficient that the paper document information  22  holds information showing whether the paper document is a master of the document and the held information is updated. In other words, it is sufficient that the paper document information  22  contains at least the paper object ID  220  and the master flag  223 . 
         [0090]      FIG. 7  is an explanatory diagram of the master flag  223  included in the paper document information according to the embodiment of this invention. 
         [0091]    When the paper document is a master of the document, “master” is recorded in the master flag field  223 . In this case, the digital/paper correspondence table  219  in the digital document information  21  becomes “locked” and it is inhibited to update the digital file (digital document). In this manner, consistency between contents printed on the paper and the contents of the digital file is maintained. 
         [0092]    On the other hand, when the paper document is not a master of the document (when the digital document is a master of the document), one of three patterns of processing is performed. First, when the contents printed on the paper and the contents of the digital file coincide with each other, “copy” is recorded in the master flag field  223 . Secondly, when the contents printed on the paper and the contents of the digital file do not coincide with each other, “out-of-date” is recorded in the master flag field  223 . Lastly, when the paper document does not exist because, for instance, the paper document has already been discarded, “discarded” is recorded in the master flag field  223 . 
         [0093]    In other words, it is possible to find which of the paper document and the digital document is a master of the document by referring to the master flag  223  in the paper document information  22 . 
         [0094]      FIG. 8  is an explanatory diagram of obtainment of relative coordinates on paper by the digital pen  14  according to the embodiment of this invention. 
         [0095]    The digital pen  14  comprises a CPU, a memory, a communication interface, a camera  141 , a battery, and a writing pressure sensor. Also, the digital pen  14  comprises a pen tip with which it is possible to write characters, symbols, and the like on paper with ink or graphite. 
         [0096]    The digital pen  14  is used together with a sheet  20  on which dots  203  for location detection have been printed. Here, the dots  203  will be described by magnifying a part  201  of the sheet  20 . On the sheet  20 , multiple small dots  203  have been printed. Those dots  203  have been printed at locations displaced from intersections (reference points)  202  of virtual lattice lines upwardly, downwardly, rightwardly, or leftwardly. 
         [0097]    When a character or a figure is annotated to the paper with the digital pen  14 , the annotated character or the like remains on the paper in such a manner that visual recognition is possible. When detecting that the pen tip has contacted the paper using the writing pressure sensor, the digital pen  14  photographs the dots  203  printed on the paper with the camera  141 . For instance, the digital pen  14  photographs an area containing six by six dots  203 . 
         [0098]    The digital pen  14  computes absolute coordinates, at which the dot pattern exists, from a combination of displacement manners of respective photographed dots. Those absolute coordinates are coordinates at which the dot pattern exists in a vast plane area. The vast plane area is an entire area in which arrangement of dot patterns without overlapping is possible. 
         [0099]    The digital pen  14  transmits the computed absolute coordinates to the client terminal  12  through the digital pen interface  13 . The client terminal  12  transmits the absolute coordinates transmitted from the digital pen  14  to the location information server  19 . The location information server  19  identifies the location (dot pattern ID) of the paper in the vast plane area and coordinates (relative coordinates) on the paper sheet based on the absolute coordinates transmitted from the digital pen  14  and transmits the identified dot pattern ID and relative coordinates to the contents server  11 A. 
         [0100]    In the manner described above, the contents server  11 A obtains the dot pattern ID and the relative coordinates from the dot pattern photographed by the digital pen  14 . 
         [0101]    Through periodic obtainment (in units of a fixed time, for instance) by the digital pen  14  of information about contact locations of the pen tip, it is possible to find movement of the pen tip. Then, the digital pen  14  transmits the absolute coordinates corresponding to the photographed dot pattern, a photographed time of the dot pattern and the pen ID to the client terminal  12 . 
         [0102]    The contents server  11 A obtains the relative coordinates from the location information server  19  based on the absolute coordinates computed by the digital pen  14 . The contents server  11 A generates a path (stroke information) of the pen tip from the obtained relative coordinates and the photographed time of the dot pattern. 
         [0103]    It should be noted here that the location information server  19  may be included in the contents server  11 A instead of being provided separately. 
         [0104]    Also, it is not required for the digital pen  14  to use the location information server  19  in order to identify the dot pattern ID and the relative coordinates. For instance, the sheet identification may be achieved using an identification number printed on the paper, a barcode printed on the paper, or an IC tag embedded in the paper. In addition, it is possible to identify locations (relative coordinates) on the sheet using a tablet. It should be noted that one of the sheet identification using an IC tag or the like and the location identification on the sheet using the tablet may be combined with the absolute coordinate identification by the location information server  19 . In this case, it becomes possible to alleviate a load of processing in which the document management system identifies the dot pattern ID and the relative coordinates. 
         [0105]      FIG. 9  shows an example of a stroke set  26  according to the embodiment of this invention. 
         [0106]    The stroke set  26  is a set of strokes of characters “Tokyo”  311  annotated with the digital pen  14 . In this embodiment, as shown in the drawing, a left upper corner is set as an origin, a horizontal direction is set as an X axis, and a vertical direction is set as a Y axis, thereby determining locations of the strokes. 
         [0107]    As described above, the stroke set is a collection of mutually related lines (strokes) and is identified based on written times of the lines and/or location relations among the lines. 
         [0108]      FIG. 10  is a diagram of configuration of the stroke set information  24  among the stroke information  23  stored in the contents server  11 A according to the embodiment of this invention. In  FIG. 10 , stroke set information for the stroke set  26  shown in  FIG. 9  is illustrated. 
         [0109]    The stroke set information  24  contains, for each stroke set, a stroke set ID  241 , a pen ID  242 , an initial annotation date and time  243 , a corresponding rectangle coordinate  244 , a number of strokes  245 , and stroke information  246 . 
         [0110]    The stroke set ID  241  is a unique identifier of the stroke set. The pen ID  242  is a unique identifier of the digital pen  14  used to annotate the stroke set. 
         [0111]    The initial annotation date and time  243  is a date and time of initial annotation of the stroke set. The corresponding rectangle area  244  is a rectangle area containing the stroke set. The corresponding rectangle area  244  is coordinates (relative coordinates) on a document, on which the stroke set has been annotated, and is expressed by a coordinate of a left upper corner of the rectangular area and a coordinate of a right lower corner. 
         [0112]    The number of strokes  245  is the number of lines (strokes) contained in the stroke set. Multiple pieces of stroke information  246 , whose number is equal to the number of strokes  245 , are recorded. Each piece of stroke information  246  contains a number of sampling points  246 A and serial numbers  246 B. 
         [0113]    The number of sampling points  246 A is the number of relative coordinates that constitute a corresponding stroke and have been obtained by the digital pen  14 . Each serial number  246 B is a unique identifier of one of the relative coordinates, which constitute the stroke and have been obtained by the digital pen  14 , and is a link to the stroke coordinate information  25  ( FIG. 11 ). 
         [0114]      FIG. 11  is a diagram of configuration of the stroke coordinate information  25  of the stroke information  23  stored in the contents server  11 A according to the embodiment of this invention. 
         [0115]    The stroke coordinate information  25  contains, for each relative coordinate obtained by the digital pen  14 , a serial number  251 , an X coordinate  252 , a Y coordinate  253 , and an obtainment time  254 . 
         [0116]    The serial number  251  is a unique identifier of the relative coordinate obtained by the digital pen  14 . The X coordinate  252  is a relative coordinate in a direction of the X axis shown in  FIG. 9  and is expressed in units of millimeters, for instance. The Y coordinate  253  is a relative coordinate in a direction of the Y axis shown in  FIG. 9  and is expressed in units of millimeters, for instance. The obtainment time  254  expresses an obtainment time of the relative coordinates by the digital pen  14 . It should be noted that in an example shown in  FIG. 11 , in the obtainment time field  254 , an elapsed time from an initial annotation time is recorded. 
         [0117]      FIG. 12  is a diagram of configuration of the user information  27  stored in the contents server  11 A according to the embodiment of this invention. 
         [0118]    The user information  27  contains, for each user, a user ID  271 , a name  272 , a section  273 , a position  274 , and a possession pen ID  275 . 
         [0119]    The user ID  271  is a unique identifier of the user. The name  272  is the name of the user. The section  273  is a section of a company or the like to which the user belongs. The position  274  is a position of the user in the company or the like. 
         [0120]    The possession pen ID  275  is a unique identifier of the digital pen  14  possessed by the user. 
         [0121]    Next, processing in the document management system according to the embodiment of this invention will be described. 
         [0122]      FIG. 13  is a flowchart of digital document update according to the embodiment of this invention. 
         [0123]    When a paper document  102  is printed from a digital document  101  ( 103 ) and the printed paper document  102  has been set as a master of the document, the master flag  223  for the paper document  102  is set at “master” and the digital/paper correspondence table  219  for the digital document  101  is set at “locked”. 
         [0124]    Following this, when a user annotates characters or the like to the paper document  102  that is a master of the document with the digital pen  14 , the contents of the paper document  102  are changed. When doing so, when the user sets the digital document  101  as a master of the document, the paper document  102  becomes a non-master of the document and the master flag  223  for the paper document  102  becomes “copy” ( 104 ). Also, the digital/paper correspondence table  219  for the digital document  101  is set at “master” and the digital document  101  is set as a master of the document ( 105 ). 
         [0125]    Following this, when the master of the document is edited, the digital document  101  is updated and the digital/paper correspondence table  219  for the digital document  101  remains “master” ( 106 ). As a result, consistency between the digital document  101  and the paper document  102  is lost, so the master flag  223  for the paper document  102  is set at “out-of-date” ( 107 ). 
         [0126]    Next, the details of each processing will be described. 
         [0127]      FIG. 14  is a flowchart of paper document print processing according to the embodiment of this invention. 
         [0128]    First, a user operates the client terminal  12  to instruct creation of a paper document by designating a document. When doing so, the user designates whether the generated paper document should be set as a master of the document. 
         [0129]    When the client terminal  12  receives the paper document creation instruction, a print process is activated and information about the designated document is sent to the contents server  11 A (S 111 ). The contents server  11 A selects a master of the document designated by the client terminal  12  by referring to the digital/paper correspondence table  219  in the digital document information  21  and the master flag  223  in the paper document information  22  and reads a corresponding digital document that is the master of the document from the contents database (S 112 ). It should be noted that when the master of the document is not the digital document, the print processing may be terminated due to an error. 
         [0130]    Following this, the contents server  11 A transmits data of the read digital document to the printer. The printer generates a paper document by printing the data of the digital document along with a predetermined dot pattern (S 113 ). Also, the contents server  11 A registers a new record in the paper document information  22 . Further, the contents server  11 A increments the number of print paper objects  218 A in the digital document information  21  and registers a newly registered paper object ID of the paper document as a paper object ID  218 B in the digital document information  21 . 
         [0131]    Following this, the contents server  11 A judges whether the printed paper document has been designated as a master of the document (S 114 ). When it is found as a result of the judgment that the paper document has been designated as a master of the document, the master flag  223  of the newly registered paper document information  22  is set at “master” (S 115 ). In addition, the digital/paper correspondence table  219  for the corresponding digital document is set at “locked”. 
         [0132]    On the other hand, when it is not found as a result of the judgment that the paper document has been designated as a master of the document, the master flag  223  in the newly registered paper document information  22  is set at “copy” (S 117 ). In this case, the digital/paper correspondence table  219  for the corresponding digital document remains at “master”. 
         [0133]      FIG. 15  is a flowchart of processing at the time of writing to a paper document according to the embodiment of this invention. 
         [0134]    When a user annotates something to a paper document using the digital pen  14 , the digital pen  14  photographs a dot pattern of the paper document that is an annotation target, identifies absolute coordinates of a location of the annotation, and sends the identified absolute coordinates to the contents server  11 A. The contents server  11 A refers to the dot pattern ID  221  in the paper document information  22  based on the identified absolute coordinates and identifies the paper document (paper object ID  220 ) that is the annotation target. Following this, the contents server  11 A judges whether the identified paper document is a master of the document by referring to the master flag  223  for this paper document (S 121 ). 
         [0135]    When it is found as a result of the judgment that the master flag  223  is set at “out-of-date”, this means that the contents printed on the paper and the contents of a corresponding digital file do not coincide with each other, so a warning that the contents printed on this paper document are not the latest contents is issued to the user (S 122 ). The warning may be issued by emitting a warning sound from the digital pen  14  or vibrating the digital pen  14 . 
         [0136]    Also, when it is found as a result of the judgment that the master flag  223  is set at “copy”, this means that the contents printed on the paper and the contents of the digital file coincide with each other, so the annotation to the paper document is permitted. Then, the digital pen  14  obtains stroke data and transfers the obtained data to the client terminal  12  without issuing the warning (S 123 ). 
         [0137]    The client terminal  12  transfers the received stroke data to the contents server  11 A. The contents server  11 A generates the stroke information  23  and increments the number of stroke sets  228 A in the paper document information  22 . Then, the contents server  11 A records a stroke set ID  241  in the generated stroke information as a stroke set ID  228 B (S 124 ). 
         [0138]    On the other hand, when it is found as a result of the judgment that the master flag  223  is set at “master”, this means that the paper document is a master of the document, so the annotation to the paper document is permitted. Then, the digital pen  14  obtains stroke data and transfers the obtained data to the client terminal  12  without issuing the warning (S 125 ). 
         [0139]    The client terminal  12  transfers the received stroke data to the contents server  11 A. The contents server  11 A generates stroke information  23  and increments the number of stroke sets  228 A in the paper document information  22 . Then, the contents server  11 A records a stroke set ID  241  in the generated stroke information as a stroke set ID  228 B (S 126 ). 
         [0140]    Following this, it is judged whether the annotated paper document should remain as a master of the document (S 127 ). For instance, in a meeting attendance table shown in  FIG. 18 , by touching “set digital document as master” with the digital pen, it is possible to make a selection in which a digital document is set as a master of the document. 
         [0141]    When it is found as a result of the judgment that the annotated paper document should remain as a master of the document, this processing is ended. 
         [0142]    On the other hand, when it is found as a result of the judgment that the annotated paper document should be set as a duplication and the digital document, in which the annotation with the digital pen has been reflected, should be set as a master of the document, the digital/paper correspondence table  219  in the digital document information  21  is changed to “master” (S 128 ). Then, the file of the digital document is read and a digital file, in which stroke data has been reflected, is generated. Next, the digital file  210  in the digital document information is updated. It should be noted that when the already-existing digital file is overwritten, there is no necessity to update the digital file name  210 . 
         [0143]    Following this, the master flag  223  for the annotated paper document is changed to “copy” (S 130 ). In addition, other related paper documents are identified by referring to the paper object IDs  218 B in the digital document information  21 . Then, each identified paper document has contents that do not coincide with the contents of the digital document, so the master flag  223  for the paper document is set at “out-of-date” (S 130 ). 
         [0144]      FIG. 16  is a flowchart of digital document update processing according to the embodiment of this invention. 
         [0145]    When receiving a request to update a digital document from the client terminal  12 , the contents server  11 A judges whether the digital document is a master of the document by referring to the digital/paper correspondence table  219  in the digital document information  21  (S 131 ). 
         [0146]    When it is found as a result of the judgment that the digital/paper correspondence table  219  is set at “locked”, this means that the digital document is not a master of the document, so a change to the digital document is rejected (S 135 ). 
         [0147]    On the other hand, when it is found as a result of the judgment that the digital/paper correspondence table  219  is set at “master”, this means that the digital document is a master of the document, so a change to the digital document is permitted. Then, a new digital document file is overwritten on an already-existing digital document file (S 132 ). It should be noted that the digital file  210  in the digital document information  21  may be updated by saving a digital document file having a different file name. 
         [0148]    Following this, it is judged whether any paper document printed from this digital document exists by referring to the number of print paper objects  218 A in the digital document information  21  (S 133 ). 
         [0149]    Then, when it is found as a result of the judgment that the number of print paper objects  218 A is not “0”, this means that at least one paper document printed from this digital document exists, so each paper document printed from this digital document is identified by referring to the paper object IDs  218 B. Next, the identified paper document has printed contents that do not coincide with the contents of the digital document, so the master flag  223  for the paper document is set at “out-of-date” (S 134 ). 
         [0150]      FIG. 17  is a flowchart of paper document discarding processing according to the embodiment of this invention. 
         [0151]    At the time of discarding a paper document using the document discarding unit  15 , a user designates a method of discarding the paper document (S 141 ). This discarding method designation is performed with the operation input unit  154  of the document discarding unit  15 . Alternatively, the user may designate the paper document discarding method by, in the meeting attendance table shown in  FIG. 18 , touching “discard completely”  311  or “discard only paper”  312  with the digital pen. 
         [0152]    The paper discriminating unit  153  photographs a dot pattern of the paper document to be discarded, identifies absolute coordinates of an annotation location, and sends the identified absolute coordinates to the contents server  11 A. 
         [0153]    The contents server  11 A identifies the paper document (paper object ID  220 ) to be annotated by referring to the dot pattern ID  221  in the paper document information  22  based on the identified absolute coordinates. Following this, the contents server  11 A judges whether the identified paper document is a master of the document by referring to the master flag  223  for this paper document (S 142 ). 
         [0154]    When it is found as a result of the judgment that the master flag is set at “master”, this means that this paper document is a master of the document, so a notification that it is inhibited to discard the paper document is issued to the user (S 146 ). This notification to the user is issued by causing the data display unit  155  of the document discarding unit  15  to display a warning and discharging the paper document that is a discarding target from the document discarding unit  15 . Alternatively, the notification may be issued by emitting a warning sound from the digital pen  14  at the time of the selection of the discarding method with the digital pen  14 . 
         [0155]    On the other hand, when it is found as a result of the judgment that the master flag is set at “copy” or “out-of-date”, this means that this paper document is not a master of the document. Therefore, it is judged which paper document discarding method has been designated (S 143 ). 
         [0156]    When it is found as a result of the judgment that the designated paper document discarding method is “discard only paper”, the document shredding unit  157  discards a thrown-in paper document by placing the document in an unusable state through shredding (S 144 ). Then, the document discarding unit  15  transmits the paper object ID of the discarded document and a master flag change request to the contents server  11 A. The contents server  11 A changes the master flag  223  for the paper document having the received paper object ID to “discarded” (S 145 ). 
         [0157]    On the other hand, when it is found as a result of the judgment that the designated paper document discarding method is “discard completely”, the paper document information  22  for this paper document is also erased. More specifically, the document shredding unit  157  discards the thrown-in paper document by placing the document in an unusable state through shredding (S 147 ). Then, the document discarding unit  15  transmits the paper object ID of the discarded document and a paper document information erasing request to the contents server  11 A. The contents server  11 A erases the paper document information  22  having the received paper object ID, erases a paper object ID  218 B corresponding to the received paper object ID from the digital document information  21 , and decrements the number of print paper objects  218 A (S 148 ). 
         [0158]      FIG. 18  is an explanatory diagram of a meeting attendance table  30  according to the embodiment of this invention. 
         [0159]    The meeting attendance table  30  is printed along with a specific dot pattern. It is possible to identify a paper object ID of this paper document through touch of the meeting attendance table by a user with the digital pen  14 . In addition, it is also possible for the contents server  11 A to identify a place that the user has touched with the digital pen  14 . 
         [0160]    In a lower area of the meeting attendance table  30 , a field for instructing to change the states of the paper document and a corresponding digital document is provided. More specifically, “discard completely”  311 , “discard only paper”  312 , and “set digital document as master”  313  are printed. 
         [0161]    As described above, when the user touches “discard completely”  311  with the digital pen  14  at the time of discarding the paper document, a method, with which erasing of the paper document information  22  is also performed in addition to the paper document discarding, is selected. Also, when the user touches “discard only paper”  312  with the digital pen  14  at the time of the paper document discarding, a method, with which the paper document information  22  is left at the time of the paper document discarding, is selected. Further, when the user touches “set digital document as master”  313  with the digital pen  14  at the time of annotation to the paper document, it is possible to make a selection in which the digital document is set as a master of the document. 
         [0162]      FIGS. 19 to 25  are each an explanatory diagram of a user interface according to the embodiment of this invention. 
         [0163]      FIGS. 19 and 20  each show an example of a user interface that associates digital documents and paper documents with each other. When a folder is selected in a left field (folder display area  401 ) in  FIG. 19 , information about digital documents (digital files) stored in the selected folder is displayed in a right upper field (digital document display area  402 ). Then, when a digital document is selected in the right upper field, each paper document printed from the selected digital document is displayed in a right lower field (paper document display area  403 ). 
         [0164]    It should be noted here that in a state where no digital document has been selected in the digital document display area  402 , each paper document printed from one of all digital documents displayed in the digital document display area  402  may be displayed in the paper document display area  403 . 
         [0165]      FIG. 20  shows a user interface in which the right fields of the screen explained with reference to  FIG. 19  have been rearranged from a vertical direction to a horizontal direction. When a folder is selected in a left field (folder display area  401 ) in  FIG. 20 , information about digital documents stored in the selected folder is displayed in a middle field (digital document display area  402 ). Then, when a digital document is selected in the middle field, each paper document printed from the selected digital document is displayed in a right field (paper document display area  403 ). 
         [0166]      FIG. 21  shows a state obtained from the screen state explained with reference to  FIG. 19  by further printing a paper document. The printed paper document “specification_print 3.prn”  404  is additionally displayed in the paper document display area  403 . 
         [0167]      FIG. 22  shows a state obtained from the screen state explained with reference to  FIG. 21  by further annotating paper documents. It is indicated that a person “A” has annotated a paper document “specification_print 2. prn” on Feb. 22, 2005 ( 405 ). Also, it is indicated that a person “B” has annotated the paper document “specification_print 3. prn” on Feb. 22, 2005 ( 406 ). 
         [0168]    When each person annotated a document is displayed, the pen ID  242  is identified by referring to the stroke set information  24  using the stroke set ID  228 B in the paper document information  22  and further identifies the name  272  of the user by referring to the user information  27 . Then, the identified name is displayed in the paper document display area  403 . 
         [0169]      FIGS. 23 and 24  each show a display example in the case where a paper document is set as a master of the document. In  FIG. 23 , for a paper document that is a master of the document, a mark (master sign  407 ) indicating that the document is a master of the document is displayed. In  FIG. 24 , a paper document that is a master of the document is highlight-displayed, thereby indicating that the document is a master of the document ( 407 ). 
         [0170]      FIG. 25  shows an example of warning display in the case where a paper document is older than a corresponding digital document. 
         [0171]    When the master flag in the paper document information  22  is set at “out-of-date”, a corresponding paper document displayed in the paper document display area is highlight-displayed ( 408 ). Alternatively, it is judged that the paper document is older than a corresponding digital document through comparison of the update date and time of the digital document and the print date and time of the paper document with each other, and based on the judgment, the paper document may be highlight-displayed. 
         [0172]    While the present invention has been described in detail and pictorially in the accompanying drawings, the present invention is not limited to such detail but covers various obvious modifications and equivalent arrangements, which fall within the purview of the appended claims.