BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to an information disclosure method and information disclosure system for permitting a server computer to create or select and then transmit page information in compliance with a client computer&#39;s request in an environment where computers, including a client computer and a server computer, are connected via a network.  
           [0002]    Due to widespread use of the Internet and advance in WWW technology, the WWW page access method for transferring page information written in HTML or XML via the Internet and displaying it on a client computer has been widely used in recent years. A method for analyzing and compiling data stored in a database and disclosing it via WWW is disclosed in JP-A No. 133892/1998 “METHOD FOR PROCESSING SERVLET, AND SYSTEM THEREFOR” (Corresponding U.S. Pat. No. 5,928,323).  
         SUMMARY OF THE INVENTION  
         [0003]    When the above prior art is used, however, the contents of generated page information are lost when it is transmitted to a client. Creating page information upon each request from a client imposes a burden on a server, making it difficult to increase the responsiveness to clients. To solve this problem, a system can be configured so as to allow a server to periodically access a database to create static pages and prevent the database from being accessed when a client accesses the server. When the system is configured in this manner, it can enhance the responsiveness to users and minimize the load on the server.  
           [0004]    In a system where pages are periodically created by a server and distributed in compliance with user requests, its responsiveness is excellent but distributed pages are not up-to-date. As a result, the distributed pages may not always meet the needs of users.  
           [0005]    In a system where pages are created upon a user&#39;s request, database access and page generation occur each time after the receipt of a user&#39;s request. As a result, the load on a server increases, rendering the responsiveness to users persistently lower than when static pages are distributed.  
           [0006]    As described above, it is difficult for the conventional method to enhance the responsiveness to users and reduce the server load while transmitting pages to meet the needs of users.  
           [0007]    It is therefore an object of the present invention to provide an information disclosure method and information disclosure system, which make it possible to judge the presence or absence of the necessity for page generation by judging whether the elapsed time from the page generation time is user-tolerable, and distribute pages to meet the needs of users while minimizing the server load.  
           [0008]    To provide pages in compliance with the needs of users, the present invention provides means for predefining a demanded freshness, which is the page freshness necessary for page access requests from users. The present invention also makes it possible to define a user-specific required freshness for disclosing the page information on a WWW server. When a page is accessed, the present invention compares the time elapsed from the page generation time with the demanded freshness and required freshness to check for the necessity of page generation, and determines whether to distribute a previously generated page or generate a new page for distribution.  
           [0009]    By using a combination of demanded freshness and required freshness concerning page access in the above manner to check for the necessity of page generation and newly generate only a required page, the present invention can distribute a page in compliance with the needs of users while keeping the server load lower than the prior art. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a system configuration diagram depicting an information disclosure method of the present invention;  
         [0011]    [0011]FIG. 2 is a diagram showing a cache computer&#39;s typical page management table that is used in a cache management processing unit;  
         [0012]    [0012]FIG. 3 is a diagram showing a server computer&#39;s typical user management table that is used in a page selection processing unit;  
         [0013]    [0013]FIG. 4 is a diagram showing a server computer&#39;s typical page management table that is used in a page selection processing unit;  
         [0014]    [0014]FIG. 5 is a flowchart depicting the process of a cache management processing unit;  
         [0015]    [0015]FIG. 6 is a flowchart depicting the process that a page selection processing unit performs to generate a page upon a user&#39;s request; and  
         [0016]    [0016]FIG. 7 is a flowchart depicting the process that a page automatic update processing unit performs to generate a page independently of a user&#39;s request. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]    Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.  
         [0018]    [0018]FIG. 1 is a system block diagram that shows a configuration of the present invention when it comprises a client computer, a cache computer, and a server computer. The client computer  10 , cache computer  20 , and server computer  30  are interconnected via networks.  
         [0019]    On the client computer  10 , a WWW browser  11  runs as a viewer that the users use to acquire and view page information. Although the present embodiment assumes that the users use a WWW browser as a viewer, the present invention remains effective when a viewer other than a browser is used. The client computer  10 , cache computer  20 , and server computer  30  are equipped each with a storage device for storing one or more programs, and the respective processors perform processing operations in accordance with the stored programs. Further, these computers are provided each with a device for connecting to a network.  
         [0020]    The cache computer  20  includes a cache management processing unit  21  and a secondary storage  22 . A major role of the cache computer  20  is to cache the page information for transfer from the server computer  30  to the client computer  10  so that whenever two or more client computers issue a request for accessing the same page, the cache computer  20  can return the cached page to the client computers without making a request to the server computer for the latest page information. The secondary storage  22  stores a page management table  23  for managing a list of cached pages, and page data  24 , which are the real data about cached pages. Under normal conditions, a large number of page data  24  exist. The page management table  23  will be described in detail later. The present invention is also applicable to a system configuration from which the cache computer  20  is removed due to cost or user request considerations.  
         [0021]    The server computer  30  comprises a WWW server  31 , a page selection processing unit  32 , which responds to a page acquisition request received via the WWW server by determining whether the server computer  30  should return a previously generated page stored in a secondary storage or generate a new page, a page generation processing unit  33  for performing a new-page generation process, a secondary storage  35 , and a DBMS  39 . The secondary storage  35  stores a user management table  36 , a page management table  37 , and page data  38  that are cached data about previously generated pages. The table information will be described in detail later. The DBMS  39  stores the data that the page generation processing unit references at the time of page generation. Although the DBMS  39  is positioned within the server computer  30  in the present embodiment, it may alternatively be placed within a DBMS server other than the server computer  30 .  
         [0022]    The structures of the tables used in the present embodiment will now be described with reference to FIGS.  2  to  4 . The field structures indicated in these figures are merely examples. Tables having a field structure different from those indicated in the figures will be readily adapted for use with the present invention.  
         [0023]    [0023]FIG. 2 shows the structure of the page management table  23 , which is used in the cache management processing unit  21  of the cache computer  20 . This table  23  has four fields, which respectively carry a server name  231  for indicating which storage location in which server a cached file is acquired from, a file name  232 , a generation time  233  for indicating the time of generation within the server computer, and a cache location  234  for indicating the storage location of page data  24  in the secondary storage  22 . Each time the page data  24  is cached in the cache computer  20 , a new record is added. Each time the page data  24  is updated with new page information, the record generation time  233  is updated.  
         [0024]    [0024]FIG. 3 shows the structure of the user management table  36 , which is used in the page selection processing unit  32  and page automatic update processing unit  34  of the server computer  30 . This table  36  has three fields, which respectively carry a user name  361  for indicating the names of users authorized to access a page, a file name  362  for indicating the file name for the page stored in the secondary storage  35 , and a required freshness  363  for indicating the freshness required for offering the page to a user. As regards the user name  361 , one record need not always be furnished for each user. Alternatively, a group name may be assigned to a separately defined group of users. The required freshness  363  indicates the page distribution time limit that should not be exceeded by the difference between the page generation time and the user&#39;s access time. If the required freshness is 0, it means that page generation is always needed for each access.  
         [0025]    [0025]FIG. 4 shows the structure of the page management table  37 , which is used in the page selection processing unit  32  and page automatic update processing unit  34  of the server computer  30 . This table  37  has two fields, which respectively carry a file name  371  for indicating the path to a page stored in secondary storage  35  and a generation time  372  for indicating the time at which the page was generated.  
         [0026]    The flowcharts in FIGS.  5  to  7  indicate the processing steps related to the present invention. FIG. 5 shows the process that is performed by the cache management processing unit  21  of the cache computer  20 . FIG. 6 shows the process that is performed by the page selection processing unit  32  of the server computer  30 . FIG. 7 shows the process that is performed by the page automatic update processing unit  34  of the server computer  30 .  
         [0027]    The flowchart in FIG. 5 will now be used to describe the processing steps that the cache management processing unit  21  performs when a user acquires a page from a WWW browser  11  for browsing purposes.  
         [0028]    In step  2101 , a request for page acquisition is received from the WWW browser  11 . In the next step  2102 , the page management table  23  on the cache computer  20  is searched with a server name  231  and file name  232  used as the search keys in order to check whether the requested page is cached in the secondary storage  22 . If the requested page is not cached, step  2109  is performed next (step  2103 ).  
         [0029]    If the requested page is cached, in step  2104 , it is checked whether the demanded freshness for the requested page is included in the page acquisition request from the WWW browser  11 . If the demanded freshness is not included, step  2108  is performed next (step  2105 ).  
         [0030]    If the demanded freshness is included, in step  2106 , the time elapsed from the generation time  233  indicated in the page management table  23  is calculated and the calculated elapsed time is compared with the demanded freshness. If the demanded freshness value is smaller than the calculated elapsed time value, the cached page is older than requested by the user. In this instance, step  2109  is performed next in order to acquire new page information from the server computer  30  (step  2107 ).  
         [0031]    If the demanded freshness value is greater than the calculated elapsed time value, on the other hand, the cached page is newer than requested by the user. In this instance, the user&#39;s request can be answered by returning the page cached in the cache computer  20 . Therefore, the page data  24  designated in the field of cache location  234  is transmitted to the WWW browser to end the cache management process (step  2108 ).  
         [0032]    If the requested page is not cached or the cached page data is older than requested by the user, the server computer  30  is requested to generate a new page. In step  2109 , the WWW server  31  is accessed to acquire the new page. The internal process of the WWW server  31  will be described later. The next step  2110  is then performed to store the acquired page data in the secondary storage  22  and update the page management table  23 . Subsequently, the page data is transmitted to the WWW browser  11  to end the cache management process (step  2108 ). To enhance the responsiveness to the WWW browser, the page data may alternatively be transmitted to the WWW browser  11  prior to step  2110 .  
         [0033]    The flowchart in FIG. 6 will now be used to describe the processing steps that the page selection processing unit  32  performs upon receipt of a page acquisition request from the cache computer  20 .  
         [0034]    In step  3201 , a page acquisition request is received from the cache computer  20 . In the next step  3202 , the page management table  37  on the server computer  30  is searched with a file name  371  used as the search key in order to check whether the requested page is cached in the secondary storage  35 . If the requested page is not cached, step  3209  is performed next (step  3203 ).  
         [0035]    If the requested page is cached, in step  3204 , the user management table  36  is searched with a user name  361  and file name  362  used as the search keys to acquire the required freshness. The time elapsed from the generation time  372  indicated in the page management table  37  is calculated and then compared with the required freshness. If the required freshness value is smaller than the calculated elapsed time value, the cached page is too old for the requesting user. Therefore, step  3209  is performed next in order to acquire new page information from the page generation processing unit  33  (step  3205 ).  
         [0036]    If the required freshness value is greater than the calculated elapsed time value, on the other hand, the cached page is fresh enough for disclosure to the requesting user. Therefore, the demanded freshness is confirmed subsequently. In step  3206 , it is checked whether the demanded freshness for the page is included in the page acquisition request from the cache computer  20 . If the demanded freshness is not included, it is concluded that the freshness is adequate. If the demanded freshness is included, on the other hand, the time elapsed from the generation time  372  indicated in the page management table  37  is calculated to compare the elapsed time with the demanded freshness. If the demanded freshness value is smaller than the elapsed time value, the cached page is older than requested by the user. Therefore, step  3209  is performed next in order to acquire new page information from the page generation processing unit  33  (step  3207 ).  
         [0037]    If the demanded freshness value is greater than the elapsed time value, the cached page is newer than requested by the user. In this instance, the user&#39;s request can be answered by returning the page cached in the secondary storage  35 . The page data  38  designated by a file name  371  in the page management table  35  is therefore transmitted to the cache computer  20  via the WWW server  31 . The page selection process is then ended (step  3208 ).  
         [0038]    If the page fails to comply with either the required freshness or the demanded freshness, the page generation processing unit  33  is called in step  3209  to acquire the generated latest page data. In step  3210 , then the acquired page data is stored in the secondary storage  35  and the page management table  37  is updated. Subsequently, the page data is transmitted to the cache computer  20  via the WWW server  31  to end the page selection process (step  3208 ). To enhance the responsiveness of the WWW server  31 , the page data may alternatively be returned to the WWW server  31  prior to step  3210 .  
         [0039]    If the employed system configuration does not include the cache computer  20 , the cache computer  20  is replaced by the WWW browser  11 ; however, such a system configuration will be readily adapted for use with the present invention.  
         [0040]    The flowchart in FIG. 7 will now be used to describe the processing steps that the page automatic update processing unit  34  performs to update page data  38  in the secondary storage  35  of the server computer  30  independently of access via the WWW server  31 . When a page update is actively performed within the server computer  30 , the responsiveness to access from the cache computer  20  or WWW browser  11  can be enhanced.  
         [0041]    In step  3401 , the user management table  36  and page management table  37  of the server computer  30  are comprehensively searched for a file name  362  and file name  371  to acquire a file name, required freshness  363 , and generation time  372 . If the user management table  36  contains two or more records having the same file name  362  and a plurality of required freshness values, the smallest required freshness value should be selected. Then, a list of files whose elapsed time from the generation time  372  is greater than the value of the required freshness  363  is prepared.  
         [0042]    In step  3402 , the prepared file list is checked for unprocessed files. When no unprocessed file remains in the list, the page automatic update process ends. If any unprocessed file is left, steps  3403  and beyond are performed.  
         [0043]    In step  3403 , the page generation processing unit  33  is called to acquire new page data. In step  3404 , the acquired page data is stored in the secondary storage  35  and the page management table  37  is updated. After deleting the associated file name from the prepared file list, the process returns to step  3402 .  
         [0044]    As described above, the present embodiment introduces the demanded freshness and required freshness data into page management by a cache computer and server computer, making it possible to distribute page data in compliance with user-specific freshness requirements while reducing the load on a server computer and providing increased responsiveness.
The present invention makes it possible to define the page freshness that is required for the page information to be disclosed or auser's page information acquisition request. A cache computer and a server computer both consider the required freshness. If the freshness is adequate, a cached static page is returned immediately. If the freshness is not adequate, on the other hand, a dynamic page generation process is performed. Further, the page information in the server computer is updated independently of a user's access request.