Abstract:
In order to make possible a variety of database searches, image data is registered on a first hard disk and a plurality of attribute tables each containing attribute information regarding images are registered on a second hard disk. When one search condition has been applied, a search of attribute information is conducted using one attribute table conforming to the search condition from among the attribute tables stored on the second hard disk. When another search condition has been applied, a search of attribute information is conducted using another attribute table stored on the second hard disk. Thus, a database can be searched even when search conditions differ.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a database search system and method. 
     2. Description of the Related Art 
     Image data representing a number of images is stored in an image database. By providing search conditions, image data representing an image that conforms to the search conditions is retrieved from the database and output. Attribute information regarding an image (incidental information such as date of photography of the image, place of photography and name of the photographer) also is associated with the image data. Depending upon the database, not only the image data but also the attribute information concerning this image data can be obtained. 
     In an image database from which attribute information is obtained in addition to image data, the image data and attribute information are stored in one-to-one correspondence in the same table within the same database. As a consequence, there are instances where a search is possible with regard to a certain prescribed search condition but is impossible in the case of another search condition. In such instances the database must be reconstructed from the beginning in order to make it possible to search the database under other search conditions as well. 
     DISCLOSURE OF THE INVENTION 
     An object of the present invention is to make possible various database searches in a system of a single type. 
     According to a first aspect of the present invention, the foregoing object is attained by providing a database search system comprising: an image database in which image data representing images is stored; an attribute information database in which there is stored an attribute information table for storing attribute information regarding image data, which has been stored in the image database, in association with search items; a link information database in which there is stored link information for linking attribute information that has been stored in the attribute information table and image data that has been stored in the image database; an attribute information search unit (attribute information search means) which, on the basis of a given search condition and link information that has been stored in the link information database, is for retrieving and outputting attribute information conforming to the search condition from the attribute information table that has been stored in the attribute information database; and an image data search unit (image data search means) which, on the basis of a given search condition and link information that has been stored in the link information database, is for retrieving and outputting image data that has been stored in the image database. 
     The first aspect of the present invention provides also a method suited for use in the system described above. Specifically, the method comprises the steps of: storing image data representing images in an image database; storing, in an attribute information database, an attribute information table for storing attribute information regarding image data, which has been stored in the image database, in association with search items; storing, in a link information database, link information for linking attribute information that has been stored in the attribute information table and image data that has been stored in the image database; on the basis of a given search condition and link information that has been stored in the link information database, retrieving and outputting attribute information conforming to the search condition from the attribute information table that has been stored in the attribute information database; and on the basis of a given search condition and link information that has been stored in the link information database, retrieving and outputting image data that has been stored in the image database. 
     Thus, in accordance with the first aspect of the present invention, the image data is stored in the image database, the attribute information table is stored in the attribute information database and the link information is stored in the link information database. 
     When a search condition is given, a search is conducted based upon the given search condition and the link information that has been stored in the link information database. Attribute information conforming to the given search condition is retrieved and output from the attribute information table that has been stored in the attribute information table. Further, a search is conducted based upon a search condition and the link information table, and image data that has been stored in the image database is retrieved and output. 
     The image database in which the image data is stored and the attribute information database in which the attribute information table is stored are separate databases (though they need not necessarily be physically separate and can be separate in logical terms). As a result, it is possible to revise the content of the attribute information table, add to the attribute information table and delete from the attribute information table independently of the image data. A database search that accommodates not only a certain specific search condition but also a variety of search conditions can be conducted. 
     A plurality of attribute information tables can be stored in the attribute information database. In such case an attribute information table that is to be searched would be searched for among the plurality of attribute information tables, which have been stored in the attribute information database, based upon a given condition and link information that has been stored in the link information database, and attribute information conforming to this search condition would be retrieved and output from the attribute information table that has been found. 
     Thus, an attribute information table to be searched is found among the plurality of attribute information tables in accordance with a given search condition and a search is conducted using the attribute information table found. This makes possible a database search for accommodating not only a certain specific search condition but also a variety of search conditions. 
     When an attribute information table conforming to a given search condition and that is to be searched has not been stored in the attribute information database, it will suffice to generate an attribute information table that can be searched in accordance with the given search condition and store this table in the attribute information database. This makes it possible to support searches in accordance with a variety of search conditions without reconstructing the attribute information table from scratch. 
     Link information that has been stored in the link information database includes first information for linking a given search condition and an attribute information table, and second information for linking a given search condition and image data, by way of example. 
     Identification codes for identifying the image data may be attached. In such case link data having a plurality of digits for linking the identification codes and the attribute information would be stored in the link information table. The link data and the identification codes would be associated with each other by the data of each digit of the link data. 
     An arrangement may be adopted in which the attribute information table is generated, it is determined whether the generated attribute information table has been stored in the attribute information database, and in response to a determination that the generated attribute information table has not been stored in the attribute information database, the generated attribute information table is stored in the attribute information database. 
     A new attribute information table can be stored in the attribute information database. Moreover, since it is determined whether the above-mentioned attribute information table has already been stored in the attribute information database, it will not duplicate an attribute information table that has already been stored in the attribute information database. 
     An arrangement may be adopted in which the link information that corresponds to the stored attribute information table is generated, responsive to storage of the generated attribute information table in the attribute information database, and the generated link information is stored in the link information database. 
     Thus, it becomes possible to link the attribute information contained in the attribute information table newly stored in the attribute information database and the image data that has been stored in the image database. 
     According to a second aspect of the present invention, the foregoing object is attained by providing a database search system comprising: an attribute information database in which there have been stored a plurality of attribute information tables for storing attribute information in association with search items; a link information database in which there is stored link information for specifying an attribute information table to be used in accordance with a given search condition from among the plurality of attribute information tables that have been stored in the attribute information database; and an attribute information search unit (attribute information search means) which, on the basis of a given search condition and link information that has been stored in the link information database, is for searching for an attribute information table to be searched among the plurality of attribute information tables that have been stored in the attribute information database, and retrieving and outputting attribute information conforming to the search condition from the attribute information table that has been found. 
     The second aspect of the present invention provides also a method suited for use in the system described above. Specifically, the method comprises the steps of: storing, in an attribute information database, a plurality of attribute information tables for storing attribute information in association with search items; storing, in a link information database, a plurality of items of link information for specifying an attribute information table to be used in accordance with a given search condition from among the plurality of attribute information tables that have been stored in the attribute information database; and, on the basis of a given search condition and link information that has been stored in the link information database, searching for an attribute information table to be searched among the plurality of attribute information tables that have been stored in the attribute information database, and retrieving and outputting attribute information conforming to the search condition from the attribute information table that has been found. 
     Thus, in accordance with the second aspect of the present invention, an attribute information table to be searched is found from among a plurality of attribute information tables in accordance with a given search condition, and a search is conducted using the attribute information table that has been found. A database search that accommodates not only a certain specific search condition but also a variety of search conditions can be conducted. 
    
    
     Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates the overall configuration of an image database system; 
     FIG. 2 is a block diagram illustrating the electrical construction of a client computer; 
     FIG. 3 is a block diagram illustrating the electrical construction of a general database server; 
     FIGS. 4 and 5 illustrate attribute tables; 
     FIG. 6 illustrates an image search table; 
     FIG. 7 illustrates an attribute search table; 
     FIGS. 8 and 9 illustrate binding tables; 
     FIGS. 10 a  and  10   b  illustrate examples of images represented by image data that has been registered; 
     FIGS. 11 a  to  11   f  illustrate examples of images represented by image data that has been registered; 
     FIG. 12 illustrates the linkage between tables and image data; 
     FIG. 13 is a flowchart illustrating processing executed by the client computer; 
     FIG. 14 is a flowchart illustrating processing executed by the general database server; 
     FIG. 15 is a flowchart illustrating processing executed by a database server for management of attribute information; 
     FIG. 16 is a flowchart illustrating processing executed by a database server for management of image data; 
     FIG. 17 is a flowchart illustrating processing executed by the general database server; 
     FIG. 18 is a flowchart illustrating processing executed by a database server for management of attribute information; 
     FIG. 19 illustrates linkage between tables; 
     FIG. 20 is a flowchart illustrating processing executed by the general database server; 
     FIG. 21 is a flowchart illustrating processing executed by a database server for management of attribute information; 
     FIG. 22 is a flowchart illustrating processing executed by a database server for management of image data; and 
     FIG. 23 illustrates the linkage between tables and image data. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A preferred embodiment of the present invention will now be described in detail with reference to the drawings. 
     FIG. 1 illustrates an overview of an image database system according to a preferred embodiment of the present invention. 
     As shown in FIG. 1, the image database system comprises a client computer  1 , a general database server  20 , a database server  30  for management of image data and a database server  40  for management of attribute information. 
     The general database server  20 , database server  30  for management of image data, database server  40  for management of attribute information and client computer  1  are capable of communicating data with one another via a network such as the Internet. 
     A hard disk (database)  23  is connected to the general database server  20 . A binding table, attribute search table and image search table (described later) have been stored (registered) in the hard disk  23 . 
     A hard disk  41  is connected to the database server  40  for management of attribute information. The hard disk  41  stores a plurality of attribute tables, described later. Though only one hard disk  41  is illustrated, it goes without saying that a plurality of hard disks can be used. Further, a plurality of the database servers  40  for management of attribute information can be used. 
     A hard disk  31  is connected also to the database server  30  for management of image data. This hard disk  31  stores image data, as will be described later. The database server  30  for management of image data also can employ a plurality of the hard disks. Further, it goes without saying that a plurality of the database servers  30  for management of image data can be used. 
     An overview of processing executed by the image database system according to this embodiment will now be described. 
     A search condition is entered from the client computer  1 . Data representing the entered search condition is transmitted to the general database server  20  via the network. The attribute table that is the object of the search is searched for by the general database server  20  based upon the search condition. Using the attribute table that has been found by the search, the database server  40  for management of attribute information searches the attribute information that has been stored in this attribute table. The attribute information retrieved is transmitted to the general database server  20 . 
     Image data that conforms to the search condition is searched for in the database server  30  for management of image data, and image data that has been found by the search is transmitted from the database server  30  for management of image data to the general database server  20 . 
     The attribute information and the image data are transmitted to the client computer  1  by the general database server  20 . The image represented by the image data and the attribute information are displayed on the display unit of the client computer  1 . 
     The details of processing in the image database system will be described below. 
     FIG. 2 is a block diagram illustrating the electrical construction of the client computer  1 . 
     The overall operation of the client computer  1  is controlled by the CPU  9 . 
     The client computer  1  includes a hard disk (HD)  2  for storing prescribed data; a hard-disk (HD) drive  3  for accessing the hard disk  2 ; a data receiving circuit  4  for receiving data transmitted via the network; a data transmitting circuit  8  for transmitting data via the network; a display unit  5  for displaying the image and attribute information in the manner described above; a keyboard  6  for entering search conditions and other commands; and a data analyzing circuit  7  for analyzing received data and other data. A memory  10  for temporarily storing data is connected to the client computer  1 . 
     FIG. 3 is a block diagram illustrating the electrical construction of the general database server  20 . 
     The overall operation of the general database server  20  is controlled by a CPU  25 . 
     The general database server  20  includes a data transceiver circuit  21  for receiving data transmitted via the network and transmitting data via the network; a data analyzing circuit  22  for analyzing data; and a data search circuit  24  for searching data that has been stored in the hard disk  23 . A memory  26  for temporarily storing data is connected to the general database server  20 . 
     Like the general database server  20 , the database server  40  for management of attribute information and the database server  30  for management of image data also each have a CPU, a data transceiver circuit, a data analyzing circuit, a data search circuit, a hard disk and a memory. 
     FIGS. 4 and 5 illustrate examples of attribute tables that have been stored on the hard disk  41  connected to the database server  40  for management of attribute information. The attribute tables store attribute information regarding images (namely information incidental to the images). 
     An Attribute Table  1  shown in FIG. 4 is an attribute table that concerns date of photography. 
     This attribute table includes identifiers, dates of photography (dates on which the images were captured) and places of photography (locations at which the images were captured) as search items. 
     An Attribute Table  2  shown in FIG. 5 is an attribute table that concerns subjects. 
     This attribute table includes the names of subjects, genders (genders of the subjects), ages (ages of the subjects) and birthplaces (birthplaces of the subjects) as search items. 
     FIG. 6 illustrates an example of an image search table that has been stored on the hard disk  23  connected to the general database server  20 . 
     The image search table is a table utilized when searching image data that has been stored on the hard disk  31  connected to the database server  30  for management of image data. 
     Image identification numbers, network addresses, server names, hard disk names and image file addresses (these shall be referred to as search items) have been stored in the image search table in association with image data. 
     The image identification numbers are unique numbers for identifying images represented by image data that has been stored on the hard disk  31  connected to the database server  30  for management of image data. 
     The network addresses are addresses on the network to which the database server  30  for management of image data is connected. 
     The server names are the names of the image-data management database servers  30  specified by the network addresses. 
     The hard disk names are the names of the hard disks  31  which store image data. 
     The image file addresses are addresses indicating image-data storage locations on the hard disk  31  storing the image data. 
     FIG. 7 illustrates an example of an attribute search table that has been stored on the hard disk  23  connected to the general database server  20 . 
     Attribute table identification numbers, network addresses, server names, vender names, versions, operating privilege, hard disk names, database owner names, attribute table names, attribute table main-key names, utilizing user names and passwords have been stored in the attribute search table on a per-attribute-table basis. 
     The attribute table identification numbers are unique numbers for identifying attribute tables that have been stored on the hard disk  41  connected to the database server  40  for management of attribute information. 
     The network addresses are addresses on the network to which the database server  40  for management of attribute information is connected. 
     The server names are the names of the attribute-information management database servers  40  which store the attribute tables. 
     The vender names indicate the names of the vendors of the attribute-information management database servers  40  which store the attribute tables. 
     The operating privilege indicates the names of users who have the privilege to operate (update, delete, etc.) the attribute tables. 
     The hard disk names are the names of the hard disks  41  which store the attribute tables. 
     The database owner names are the names of the users who manage the attribute tables. These names are identical with the above-mentioned names of the users having the operating privilege and the utilizing user names, described later. Of course, it goes without saying that the database owner names, the names of the users having the operating privilege and the utilizing user names may be different from one another. 
     The attribute table names are the names of the attribute tables. 
     The attribute table main-key names are names used as main keys in search conditions among search items when attribute information that has been stored in an attribute table is searched. 
     The utilizing user names are the names of users who are capable of utilizing the image database system according to this embodiment. 
     The passwords indicate the passwords of the individual users. 
     FIGS. 8 and 9 illustrate examples of binding tables that have been stored on the hard disk  23  connected to the general database server  20 . 
     A binding table is a table for linking attribute tables and image data. 
     The binding table (Binding table No.  1 ) shown in FIG. 8 is a table for linking the attribute table shown in FIG.  4  and image data that has been stored on the hard disk  31  connected to the database server  30  for management of image data. 
     This binding table stores the identifiers, which are the main keys of the attribute table (the search items which specify the attribute tables in the search conditions) shown in FIG. 4, and binding information. 
     The binding table (Binding table No.  2 ) shown in FIG. 9 is a table for linking the attribute table shown in FIG.  5  and image data that has been stored on the hard disk  31  connected to the database server  30  for management of image data. 
     This binding table stores the names of subjects, which are the main keys of the attribute table shown in FIG. 5, and binding information. 
     The binding information is for linking the attribute information of the main key and image data to which this attribute information has been attached. The binding information is composed of data consisting of a plurality of digits. The plurality of digits correspond to image identification numbers that have been stored in the image search table. 
     By way of example, the least significant digit of the binding information corresponds to Image Identification No.  1  and the next least significant digit of the binding information corresponds to Image Identification No.  2 . If binding information is “0”, then the image specified by the corresponding image identification number is not one that concerns the corresponding attribute information. If binding information is “1”, then the image specified by the corresponding image identification number is one that concerns the corresponding attribute information. Binding information does not necessarily contain only one “1” digit and may contain several “1” digits. This means that a plurality of images may be linked to attribute information by the binding information. 
     FIGS. 10 a , and  10   b  and FIGS. 11 a  to  11   f  illustrate examples of images represented by image data that has been stored on the hard disk  31  connected to the database server  30  for management of image data. 
     FIGS. 10 a  and  10   b  illustrate examples of images the attribute information of which has been stored in the attribute table illustrated in FIG.  4 . By applying date of photography (or an identifier if desired) as the main key of the search condition, the image data is searched. Image Identification No.  1 , described later, has been attached to the image illustrated in FIG. 10 a , and Image Identification No.  2  has been attached to the image illustrated in FIG. 10 b.    
     FIGS. 11 a  to  11   f  illustrate examples of images the attribute information of which has been stored in the attribute table depicted in FIG.  5 . By applying the name of a subject as the main key of the search condition, the image data is searched. Image Identification Nos.  3  to  8  have been attached to the images illustrated in FIGS. 11 a  to  11   f.    
     FIG. 12 illustrates the linkage between the above-described attribute tables, image search table, attribute search table, binding tables and image data. 
     The attribute search table and the attribute tables are linked, the attribute search table and the binding tables are linked, the binding tables and the image search table are linked, and the image search table and image data are linked. The attribute tables (and the attribute information that has been stored in the attribute tables) and the image data can be searched. 
     FIGS. 13 to  16  are flowcharts illustrating search processing executed by the image database system according to this embodiment. 
     FIG. 13 is a flowchart illustrating processing executed by the client computer, FIG. 14 is a flowchart illustrating processing executed by the general database server  20 , FIG. 15 is a flowchart illustrating processing executed by the database server  40  for management of attribute information, and FIG. 16 is a flowchart illustrating processing executed by the database server  30  for management of image data. 
     Using the client computer  1 , the user selects the desired attribute table to be searched from among the plurality of attribute tables that have been stored on the hard disk  41  connected to the database server  40  for management of attribute information (step  51  in FIG.  13 ). It is assumed here that the user already knows what attribute tables have been stored on the hard disk  41 . The user uses the keyboard  6  of the client computer  1  to enter a search condition in such a manner that the selected attribute table will become part of the search condition (step  52  in FIG.  13 ). For example, the user enters the search condition “RETRIEVE SUBJECT NAME AND BIRTHPLACE ATTRIBUTE INFORMATION FROM SUBJECT ATTRIBUTE TABLE WHERE SUBJECT NAME BEGINS WITH ‘SMITH’”. 
     When the search condition is entered from the keyboard  6  of the client computer  1 , a search formula is generated by the CPU  9  (step  53  in FIG.  13 ). On the assumption that the search condition is the above-mentioned “RETRIEVE SUBJECT NAME AND BIRTHPLACE ATTRIBUTE INFORMATION FROM SUBJECT ATTRIBUTE TABLE WHERE SUBJECT NAME BEGINS WITH ‘SMITH’”, the formula generated is “SELECT SUBJECT, BIRTHPLACE FROM SUBJECT TABLE WHERE NAME=SMITH”. 
     When the search formula is generated, data representing the formula is applied to the data transmitting circuit  8  of the client computer  1 . The latter transmits the data representing the search formula to the general database server  20  via the network (step  54  in FIG.  13 ). 
     The data representing the search formula transmitted from the client computer  1  is received by the general database server  20  (step  61  in FIG.  14 ). On the basis of the received data representing the search formula, the general database server  20  searches for the attribute table that is the object of the search from the plurality of attribute tables that have been stored in the hard disk  41  connected to the database server  40  for management of attribute information (step  62  in FIG.  14 ). More specifically, in the case of the above-mentioned search formula, the name of the attribute table is “SUBJECT”. Accordingly, the network address (NETAD 2 ) of the attribute-information management database  40  that manages the hard disk  41  storing this attribute table is found from the attribute search table. The data representing the search formula is transmitted to the attribute-information management database  40  specified by the network address that has been found (step  63  in FIG.  14 ). 
     The database server  40  for management of attribute information receives the data representing the search formula transmitted from the general database server  20  (step  71  in FIG.  15 ). Upon receiving the data representing the search formula, the database server  40  for management of attribute information searches the attribute table, which has been selected from the attribute tables stored on the hard disk  41 , for attribute information on the basis of the search formula (step  72  in FIG.  15 ). In the case of the above-mentioned search formula, the subject name having the name “SMITH” and the birthplace of this subject are found from the subject attribute table. The attribute information “SMITH, JOHN; NEW JERSEY”, “SMITH, ROBERT; VERMONT” and “SMITH, RICHARD; TEXAS” is obtained from the attribute table shown in FIG. 5 by this search. 
     The data representing the attribute information obtained by the search of the attribute table is transmitted from the database server  40  for management of attribute information to the general database server  20  (step  73  in FIG.  15 ). 
     The data representing the attribute information transmitted from the database server  40  for management of attribute information is received by the general database server  20  (step  64  in FIG.  14 ). 
     Next, the general database server  20  finds the binding table to be utilized in the search of image data and searches the binding information contained in this binding table (step  65  in FIG.  14 ). Binding table numbers have been assigned to the binding tables and the binding table numbers correspond to the identification numbers of attribute tables. When the search formula is applied to the general database server  20  in the manner described above, the server refers to the attribute search table and ascertains the identification number of the attribute table from the name of the attribute table. Since this attribute table number corresponds to a binding table number, the binding table that corresponds to the search formula is found. Binding information corresponding to the attribute information obtained by searching the attribute table is retrieved from the binding information that has been stored in the binding table found (step  65  in FIG.  14 ). 
     In the search formula mentioned above, the attribute table selected is the subject attribute table and therefore the attribute search table number is “2”. Accordingly, the binding table whose number is “2” is the binding table that should be utilized. The binding information “000100”, “01000” and “100000” corresponding to the attribute information “SMITH, JOHN”, “SMITH, ROBERT” and “SMITH, RICHARD”, which was found by the search in the manner described above, is found by searching the binding information contained in the binding table that was found. 
     As mentioned earlier, the digits of the binding information and the image identification numbers correspond, and the image identification numbers are found from the image search table. For example, the binding information of the attribute information “SMITH, JOHN” is “000100”, and the “1” digit is the third digit from the most significant digit. The image identification number, therefore, is “3”. The network address and image file addresses corresponding to the found image identification numbers are read out of the image search table. The image-data management database server  30  managing the hard disk  31  storing the image data that is to be found is specified by the network address. 
     Further, the storage locations of the image data in the hard disk  31  connected to the specified database server  30  for management of image data are known from the image file addresses. These image file addresses are transmitted as an image data search command from the general database server  20  to the image-data management database server  30  specified by the network address (step  66  in FIG.  14 ). 
     The image data search command is received by the database server  30  for management of image data (step  81  in FIG.  16 ). Image data that has been stored at the locations designated by the image file addresses are read out of the hard disk  31  in accordance with the image data search command (step  82  in FIG.  16 ). The image data read out is transmitted from the database server  30  for management of image data to the general database server  20  (step  83  in FIG.  16 ). 
     The image data that has been transmitted from the database server  30  for management of image data is received by the general database server  20  (step  67  in FIG.  14 ). 
     The general database server  20  obtains the attribute information and image data conforming to the search formula and stores the same in memory temporarily. The data representing the attribute information and the image data obtained is read out of the memory and is transmitted from the general database server  20  to the client computer  1  via the network (step  68  in FIG.  14 ). 
     The client computer  1  receives the image data and the data representing the attribute information transmitted from the general database server  20  (step  55  in FIG.  13 ). The received image data and data representing the attribute information is applied to the display unit  5  of the client computer  1 . As a result, the images represented by the image data and attribute information are displayed on the display screen of the display unit of client computer  1  (step  56 ). 
     In the embodiment described above, the images of subjects which begin with “SMITH” and the attribute information constituted by the names and birthplaces concerning these images are retrieved based upon the search condition “RETRIEVE SUBJECT NAME AND BIRTHPLACE ATTRIBUTE INFORMATION FROM SUBJECT ATTRIBUTE TABLE WHERE SUBJECT NAME BEGINS WITH ‘SMITH’”. However, other searches are also possible using the image database search system described above. For example, it is possible to conduct a search to obtain images that were shot over a certain specific period of time as well as the attribute information concerning these images, and images that were shot at a certain specific place as well as the attribute information concerning these images. It goes without saying that in a case where images that were shot over a certain specific period of time as well as the attribute information concerning these images and images that were shot at a certain specific place as well as the attribute information concerning these images are obtained by conducting a search, a “Date of Photography” attribute table and a binding table identified by Binding Table No.  1  would be used. 
     In the image database search system according to this embodiment, a plurality of attribute tables have been stored in the hard disk  41  connected to the database server  40  for management of attribute information. This means that various search conditions can be accommodated without reconstructing the database from scratch. In order to deal with a new search condition, the attribute table need only be stored on the hard disk  41 . 
     FIGS. 17 and 18 are flowcharts illustrating processing for storing a new attribute table on the hard disk  41  connected to the database server  40  for management of attribute information, in which FIG. 17 is a flowchart showing processing executed by the general database server and FIG. 18 a flowchart showing processing executed by the database server  40  for management of attribute information. 
     FIG. 19 illustrates the linkage among attribute tables, an attribute search table and a binding table. 
     An attribute table to be stored on the hard disk  41  connected to the database server  40  for management of attribute information is input at the client computer  1 . For example, an attribute table regarding place of photography (Attribute Table  3 ) is entered. Data representing the entered attribute table is transmitted from the client computer  1  to the general database server  20 . 
     The attribute table data and data indicating attribute-table registration privilege is received by the general database server  20  (step  91  in FIG.  17 ). It is determined whether an attribute table having content identical with that of the attribute table about to be stored anew on the hard disk  41  already has been stored on the hard disk  41  (step  92  in FIG.  17 ). Further, it is determined whether the user of the client computer  1  has the privilege to register the attribute table (step  93  in FIG.  17 ). If the name of the user of the client computer  1  being accessed has been stored in the attribute search table, then it construed that this user has the registration privilege. It goes without saying that data representing the user name is transmitted from the client computer  1  to the general database server  20  in order to determine whether the user possesses the registration privilege. 
     If the attribute table that the user is attempting to register anew has not been stored on the hard disk  41  (“NO” at step  92  in FIG. 17) and the user of the client computer  1  possesses the privilege to register the attribute table (“YES” at step  93  in FIG.  17 ), then the received attribute table data is transmitted from the general database server  20  to the database server  40  for management of attribute information (step  94  in FIG.  17 ). 
     The database server  40  for management of attribute information receives the attribute table data transmitted from the general database server  20  (step  97 ) and then registers the received attribute table data in the hard disk  41  (step  98 ). Since a new attribute table is registered, it is possible to accommodate a different search. 
     The general database server  20  generates a binding table concerning the attribute table that has been newly registered on the hard disk  41  (step  95  in FIG.  17 ). For example, Binding Table  3  corresponding to the Attribute Table  3  concerning place of photography is generated. 
     When the new attribute table is generated, the binding table and the data of the attribute search table corresponding to the attribute table newly registered are added to the attribute search table (step  96 ). As a result, on the basis of the attribute information obtained by the search in the manner described above, the corresponding image data can be retrieved from the hard disk  31  connected to the database server  30  for management of image data. 
     When the attribute table that the user is attempting to register has already been registered on the hard disk  41  (“YES” at step  92  in FIG.  17 ), or when the user does not possess the privilege to register the attribute table (“NO” at step  93  in FIG.  17 ), predetermined error processing is executed. 
     FIGS. 20 to  22  are flowcharts illustrating processing when image data and attribute information are registered. 
     FIG. 20 is a flowchart illustrating processing executed by the general database server  20 , FIG. 21 is a flowchart illustrating processing executed by the database server  40  for management of attribute information and FIG. 22 is a flowchart illustrating processing executed by the database server  30  for management of image data. 
     FIG. 23 illustrates the linkage among attribute tables, an attribute search table, binding tables, an image search table and image data. 
     It is assumed here that attribute information, namely the subject name “BAKER, JAMES”, gender “MALE”, age “30” and birthplace “OHIO”, and image data regarding this attribute information is to be registered. 
     The user of the client computer  1  enters the image data to be registered and the attribute information represented by this image data, and the user selects the attribute table in which the attribute information is to be registered. The entered image data and attribute information and data representing the selected attribute table are transmitted from the client computer  1  to the general database server  20 . 
     The general database server  20  receives the image data, attribute information and data identifying the selected attribute table transmitted from the client computer  1  (step  101  in FIG.  20 ). On the basis of the data identifying the selected attribute table, the attribute table in which the attribute information is to be registered is searched for by referring to the attribute search table (step  102  in FIG.  20 ). 
     If the attribute table in which the attribute information is to be registered is found by the search, the attribute information that has been received is transmitted to the attribute-information management database  40  managing the hard disk on which this attribute table has been stored (step  103  in FIG.  20 ). 
     The attribute information that has been transmitted from the general database server  20  is received by the database server  40  for management of attribute information (step  111  in FIG.  21 ). The received attribute information is registered in the selected attribute table (step  112  in FIG.  21 ). As a result, the attribute information, namely the subject name “BAKER, JAMES”, gender “MALE”, age “30” and birthplace “OHIO”, is registered in the subject attribute table. 
     Next, the image data is transmitted to the database server  30  for management of image data by the general database server  20  (step  104  in FIG.  20 ). 
     The database server  30  for management of image data receives the image data transmitted from the general database server  20  (step  121  in FIG. 22) and registers the received image data on the hard disk  31  (step  122  in FIG.  22 ). As a result, the image data is registered on the hard disk  31 . 
     When the image data is registered on the hard disk  31 , the binding table is updated (step  105 ). The image data that has been newly registered on the hard disk  31  can be searched using the binding table in the manner described above. For example, the subject name “BAKER, JAMES” and binding information “100000000” is registered in Binding Table  2 . 
     As many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.