Abstract:
A control unit configures an MFP system by combining a plurality of functional units connected to an internal network, so that this MFP system includes functions necessary as an MFP. This allows implementation of a desired function by combining a plurality of functional units connected to a network with a high degree of freedom, regardless of whether there is a failure. To inexpensively expand only necessary functions in accordance with the needs, desired functional units can be flexibly combined. When an MFP system to be discarded includes a functional unit whose life has not expired yet, this functional unit can be reused.

Description:
BACKGROUND OF THE INVENTION 
   A multifunction printing system (to be referred to as an MFP system hereinafter) realizes a plurality of functions by connecting various functional units such as a scanner unit, printer unit, image processing unit, paper feed unit, facsimile unit, and finisher unit via a system bus or the like. 
   Unfortunately, many conventional MFP systems become entirely unusable if any of these functional units fail. 
   In some conventional MFP systems, a faulty functional unit is disconnected to allow other functional units to be usable. Alternatively, if an error occurs while a printing system is operating, another MFP system connected to the network is searched for, and image data is transferred to the found MFP system to cause the system to perform print job redirecting printing. 
   This MFP system, however, merely causes another MFP system to perform print job redirecting printing as a temporary countermeasure against a failure, and cannot permanently use functional units of another MFP system regardless of whether there is a failure. In addition, the degree of freedom of combination of functional units is low, and realizable functions are limited in many respects. 
   Also, it is difficult to inexpensively expand only necessary ones of a plurality of functional units in accordance with the needs. That is, functional units are difficult to flexibly combine. 
   Furthermore, when the MFP system is to be discarded, the whole system must be discarded at once even if the system still contains a usable functional unit whose life has not expired yet. This makes the system inferior in terms of environmental protection and resource protection. 
   SUMMARY OF THE INVENTION 
   The present invention has been made in consideration of the above situation, and has as its object to provide a network MFP system capable of implementing desired functions by combining a plurality of functional units connected to a network with a high degree of freedom, regardless of whether there is a failure. 
   It is another object of the present invention to provide a network MFP system capable of flexibly combining desired functional units in order to inexpensively expand only necessary functions in accordance with the needs. 
   It is still another object of the present invention to provide a network MFP system by which a functional unit whose life has not expired yet can be reused when the MFP system is discarded. 
   A network MFP system of the present invention comprises 
   functional units each having a unique network address and connected to an internal network, and 
   a control unit connected to the functional units across the internal network to control operations of the functional units, 
   wherein the control unit implements a predetermined function by configuring an MFP system by dynamically combining the functional units for each job. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing the configuration of a network MFP system according to an embodiment of the present invention; 
       FIG. 2  is a block diagram showing the configuration of the network MFP system when functional units having equivalent functions are added; 
       FIG. 3  is a block diagram showing the hardware and software configurations of a personal computer (to be referred to as a PC hereinafter) in the network MFP system; 
       FIG. 4  is a block diagram showing an IC tag information reading unit which can be added to the network MFP system and also showing expendables; 
       FIG. 5  is a block diagram showing the arrangement of the IC tag information reading unit; 
       FIG. 6  is a view for explaining the management address and the quantity in stock/the lower-limit quantity in stock of each expendable; 
       FIGS. 7A and 7B  are flow charts showing the procedure of processing performed by the network MFP system; 
       FIG. 8  is a view for explaining combinations of functional units necessary to implement various functions; 
       FIG. 9  is a view for explaining the functions and specs of the individual functional units; 
       FIG. 10  is a flow chart showing the procedure of adding a functional unit connected to an external LAN to the network MFP system; 
       FIGS. 11A ,  11 B, and  11 C are flow charts showing the procedure of processing performed by the network MFP system; 
       FIG. 12  is a view for explaining functions necessary for jobs 1 to 7 and configurations for executing these jobs; 
       FIG. 13  is a block diagram showing combinations of functional units configured to execute jobs 1 and 2; and 
       FIG. 14  is a block diagram showing combinations of functional units configured to execute jobs 3 to 7. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. 
   A network MFP system according to the embodiment of the present invention will be explained below with reference to  FIG. 1  showing the configuration of the system. 
   As functional units for implementing various functions, an MFP  1  comprises an auto discharge and feed (ADF) unit  13  for automatically feeding and discharging originals, a scanner unit  25  for reading originals, an image processing unit  14  for receiving image data, performing predetermined image processing, and outputting the processed data, a FAX unit  15  for receiving image data and transmitting the data to a FAX line, or outputting image data received from the FAX line, a printer unit  26  for receiving and printing out image data, a finisher unit  16  for performing predetermined processing on a printout sheet, an operation unit  17  to be operated by a user, a data storage  18  for storing data, an operation/display unit  20  for displaying various data such as statuses, a double-sided unit  21  for double-sided printing, paper feed units  22 ,  23 , and  19  for storing sheets of predetermined sizes, and a housing unit  24  for housing the whole apparatus. 
   These functional units are connected to a control unit  11  across an internal LAN (Local Area Network)  27  and controlled by the control unit  11 . The control unit  11  is connected to an external LAN  41  via a router  12 . 
   The external LAN  41  is connected to an MFP  2  having a control unit  31  and router  32 , and also connected to a download server  43  across the Internet  42 . Accordingly, the control unit  11  of the MFP  1  is connected across the external LAN  41  to the control unit  31  via the routers  12  and  32 . Functional units (not shown) of the MFP  2  are connected to and controlled by the control unit  31 . 
   The functional units, control unit  11 , and router  12  of the MFP  1  have unique network IP addresses. Likewise, the functional units, control unit  31 , and router  32  of the MFP  2  have unique IP addresses. 
   The control unit  11  can exchange data, via the router  12 , with the control unit  31  of the MFP  2  connected to the external LAN  41 , and can exchange data with the download server  43  across the Internet  42 . 
   With reference to  FIG. 2 , a configuration when the control unit  11  of the MFP  1  in the above network MFP system forms another MFP by connecting and combining other functional units having equivalent functions via an internal LAN  110  will be explained below. This system is particularly effective when a specific function is to be expanded, e.g., when the processing efficiency is to be increased by operating a plurality of scanner units in parallel. However, if a plurality of functional units having equivalent functions cannot be simultaneously operated, only one functional unit can be operated while the other functional unit is used as an auxiliary unit in the event of a failure. 
   The control unit  11  of the MFP  1  connects other functional units having equivalent functions via the router  12  and internal LAN  110 , in addition to the functional units  13  to  25  described above, thereby forming a new MFP. 
   The other functional units are a finisher  71 , double-sided unit  72 , paper feed units  73  and  74 , housing unit  75 , and paper feed unit  76  of an MFP  3 , a finisher  81 , double-sided unit  82 , paper feed units  83  and  84 , housing unit  85 , and paper feed unit  86  of an MFP  4 , a data storage  91 , a remote-control operation unit  92 , an ADF unit  101 , a scanner unit  102 , and a PC  53 . In the PC  53 , a FAX unit driver  61 , image processing unit driver  62 , and display unit driver  63  are installed. 
   These functional units have unique network IP addresses. Similar to the hardware components, the driver software  61  to  63  installed in the PC  53  have virtual IP addresses. 
     FIG. 3  shows details of the arrangement of the PC  53 . 
   The control unit  11  shown in  FIG. 2  installs various driver software in the PC  53 . In addition to the FAX unit driver  61 , image processing unit driver  62 , display unit driver  63  described above, a network driver  223  is installed. 
   The PC  53  has hardware components such as a CPU  211 , I/O controller  212 , auxiliary storage  213 , main storage  214 , display controller  215 , network controller  216 , and FAX controller  217 . These hardware components have unique network IP addresses. Likewise, the installed driver software  61  to  63  and  223  have virtual IP addresses. 
   To implement functions of some of the functional units in the MFP  1  instead of these functional units, the control unit  11  installs the driver software  61  to  63  and  223  in the PC  53  and runs the software, thereby implementing desired functions. 
     FIG. 4  shows an IC tag information reading unit for managing expendables, which can be further added to the network MFP system according to this embodiment, and also shows the expendables. 
   The expendables are sheets  311 , toner  312 , fuser  313 , and others  314 . IC tags  321  to  324  describing items are attached to these expendables. 
   As shown in  FIG. 5 , the IC tag information reading unit  300  is connected to the internal LAN or external LAN, and includes an antenna  610 , short-range radio transmitter/receiver  611 , IC tag information reader  612 , interval timer  613 , expendable number discriminator  614 , data manager  615 , controller  616 , and network I/F  617 . 
   The interval timer  613  measures a predetermined time, and the IC tag information reader  612  reads IC tag information whenever the predetermined time has elapsed. That is, the short-range radio transmitter/receiver  611  inquires of an IC tag by radio via the antenna  610 , and receives information returned from the IC tag via the antenna  610 . The IC tag information reader  612  reads this IC information, and supplies the information to the expendable number discriminator  614 . 
   The data manager  615  manages a database in which pieces of IC tag information and expendable product numbers are related. The expendable number discriminator  614  uses this database managed by the data manager  615  via the controller  616 , and discriminates the product number of an expendable from the read IC tag information, thereby checking the quantity in stock of each product number. The network I/F  617  notifies the control unit  11  of this information across the internal LAN or external LAN. 
   When the received information is transmitted across the external LAN, the control unit  11  processes this information as stock management information, and forms a stock management list as shown in  FIG. 6 . The control unit  11  manages each expendable by using a unique management IP address. 
   For example, for a product number having a management IP address “XXX:XX:XX:::X:X1”, the quantity in stock of black (K) toner is 2 with respect to 2 as the lower-limit quantity in stock (quantity necessary for stock), the quantity in stock of yellow (Y) toner is 1 with respect to 0 as the lower-limit quantity in stock, the quantity in stock of magenta (M) toner is 2 with respect to 1 as the lower-limit quantity in stock, the quantity in stock of cyan (C) toner is 2 with respect to 1 as the lower-limit quantity in stock, the quantity in stock of waste toner boxes is 0 with respect to 0 as the lower-limit quantity in stock, and the quantity in stock of ozone filters is 0 with respect to 0 as the lower-limit quantity in stock. In this case, none of these expendables is smaller than the lower-limit quantity in stock. 
   For a product number having a management IP address “XXX:XX:XX:::X:X3”, however, the quantity in stock of black (K) toner is 1 with respect to 2 as the lower-limit quantity in stock. If there is a product number whose quantity in stock is smaller than the lower-limit quantity in stock as described above, the control unit  11  notifies the manager and/or the service center of this information across the external LAN  41 . 
   Also, when received information is transmitted across the internal LAN, the control unit  11  checks whether the expendable is a regular product (a genuine product or an authorized third party product), and describes the result in a part replacement log database concerning expendables. Also, the control unit  11  notifies the manager and/or the service center of the use status. 
   If the product number of an expendable is not the one of a regular product, the control unit  11  notifies the manager of a warning message indicating that, e.g., a guarantee is limited in the event of a failure. In some instances, the control unit  11  can also control the system so that the system does not operate. 
   The procedure of processing performed by the network MFP system described above will be explained below with reference to flow charts shown in  FIGS. 7A and 7B . 
   First, a control flow before the MFP system is configured will be described. 
   As shown in  FIG. 7A , the power supply of the control unit  11  is turned on in step S 10 . 
   In step S 11 , a self-diagnosis function of the control unit  11  operates to detect a failure of the control unit itself. In addition, necessary initialization is performed. 
   In step S 14 , whether the control unit  11  is abnormal is checked. If the control unit  11  is abnormal, the flow advances to step S 18  to display a message for calling a person who performs maintenance service on the operation/display unit  20 . If possible, the maintenance service center and manager are notified to that effect. This notification is performed by transmitting a message indicating the occurrence of a failure to those computers of the maintenance service center and manager, which are connected to the external LAN  41 . In this case, no more processing is possible, so the processing is immediately terminated. 
   In step S 16 , the control unit  11  transmits an activation command to the individual functional units connected to the internal LAN via the router  12 . 
   Each functional unit has a so-called wake up function by which the unit is activated by an activation command transmitted from the internal LAN. Accordingly, each functional unit receives a packet sent from the control unit  11 , and, if the functional unit determines that the packet is an activation command, a self-diagnosis function starts, and the functional unit transmits the result to the control unit  11 . 
   In step S 22 , the control unit  11  waits for a predetermined time after transmitting the activation command to the functional units and before receiving self-diagnostic results from these functional units. 
   In step S 24 , the control unit  11  checks whether there is a functional unit which has not returned a self-diagnostic result even after the predetermined time has elapsed or which has returned an error status. 
   If such a functional unit exists, the control unit  11  specifies this faulty functional unit in step S 26 . If a functional unit has returned an error status, this functional unit can be readily specified. However, a functional unit which has not returned a diagnostic result cannot be directly specified. Therefore, the control unit  11  specifies the faulty functional unit by combining, e.g., past connection log information and physical MAC address information attached to each hardware added to the LAN I/F. 
   In step S 28 , the control unit  11  notifies the system manager and the manufacturer&#39;s service center of information of the faulty functional unit, and the flow advances to step S 30 . In this case, the control unit  11  removes the faulty functional unit from the combinable configuration list, and forms an MFP system by using other functional units. 
   If the control unit  11  determines in step S 24  that there is no functional unit which has not returned a self-diagnostic result even after the elapse of the predetermined time or which has returned an error status, the flow advances to step S 30 . 
   In step S 30 , the control unit  11  checks whether an unknown functional unit is connected across the internal LAN to the control unit  11  via the router  12 . If an unknown functional unit is connected, the flow advances to step S 40 . In step S 40 , the control unit  11  accesses the download server  43  connected to the Internet  42  to specify the unknown functional unit on the basis of information such as an MAC address or the like, thereby checking whether this functional unit can be added to the configuration. If this unknown functional unit can be added to the configuration, the control unit  11  downloads a driver program, parameters, and the like which the control unit  11  requires to operate the unit, thereby performing update. After that, the flow advances to step S 50  in  FIG. 7B . 
   If no unknown functional unit is connected to the internal LAN in step S 30 , the flow advances to step S 32 , and the control unit  11  checks whether its own driver and parameters are updated. If these driver and parameters are updated and valid, the flow advances to step S 50 . 
   If the driver and parameters are invalid, the flow advances to step S 34  to check whether a similar control unit is connected to the external LAN  41 . If no such control unit is connected, the flow advances to step S 40 , and the control unit  11  downloads driver update information, a driver program, and parameters from the download server  43  connected to the Internet  42 . 
   If it is determined in step S 34  that a similar control unit is connected to the external LAN  41 , the control unit  11  checks in step S 36  whether the driver and parameters of the control unit are information whose available period has expired. If the available period has expired, the flow advances to step S 40 . If the available period has not been expired, the flow advances to step S 38 , and the control unit  11  copies the driver update information, driver program, and parameters of the control unit. 
   The control unit  11  must refer to such update information whenever the available period of its own driver and parameters has expired or the configuration of functional units has changed as will be described later. 
   The flow then advances to  FIG. 7B . After the driver and parameters are updated to the latest ones through the above processing, a configuration which can be implemented by using functional units which are connected across the internal LAN  110  to the control unit  11  via the router  12  and which normally operate is determined. 
   If the priority order of combinations is designated as will be described later, an MFP is formed by using this priority order. For example, from a combinable configuration list provided by the manufacture beforehand as shown in  FIG. 8 , the manager sometimes sets the priority order in advance when the MFP is installed. In a case like this, a configuration is determined by selecting functional units on the basis of this designated priority order. 
   If no such designated priority order of combinations is present, a combinable configuration list provided by the manufacturer beforehand is used. 
   For example, as shown in  FIG. 8 , a functional unit combination necessary to realize a color copier ( 40  sheets) as function number  01  includes an image processing unit IMG 03 , data compression/expansion unit CMP 01 , scanner unit SCND 01 , printing unit PRND 01 , and the like. 
   Also, the control unit  11  has a management table concerning the type of function, processing performance, and driver software of each functional unit as shown in  FIG. 9 . For example, an image processing unit (IP address; IMGCO 2 ) has an image processing function, color image processing capability as spec 1, and processing capability of 30 sheets/min as spec 2. In addition, two such image processing units can be simultaneously operated as spec 3, and the unit is operated by a driver of version 2.11 as spec n (n is a positive number of 1 or more). 
   As shown in step S 50 , functional units may also be added to an external configuration as needed. The control unit  11  checks whether to add to the configuration an external functional unit connected to the other control unit  31  which is connected to the control unit  11  across the external LAN  41 . If YES in step S 50 , the flow advances to  FIG. 10 . If NO in step S 50 , the flow advances to step S 52 . 
   If the external functional unit is to be added to the configuration, the flow advances to step S 110  in  FIG. 10 , and the control unit  11  checks whether the management table of the other control unit  31  is within the available period. 
   If the management table is not within the available period, the flow advances to step S 112 , and the control unit  11  searches for the external functional unit to update the management table. 
   If the management table is within the available period or after step S 112  is complete, the flow advances to step S 114  to check whether the predetermined functional unit to be added to the configuration is found. If the functional unit is found, the flow advances to step S 116 ; if not, the flow advances to step S 124 . 
   In step S 116 , the control unit  11  sends to the other control unit  31  a message requesting sharing of the external functional unit connected to the control unit  31 . 
   In step S 118 , the control unit  11  checks whether the other control unit  31  returns a message indicating denial of sharing to the control unit  11 . 
   If no sharing denial message is returned, the flow advances to step S 120 , and the control unit  11  writes information “unit sharing is permitted” in an external functional unit column of the configuration management table, and updates the version of the table. 
   If functional units connected to the external control unit  31  include a functional unit having a function equivalent to that of a functional unit connected to the internal LAN, the control unit  11  preferentially adds this functional unit connected to the internal LAN to the MFP system configuration. This further improves the operation stability. 
   On the other hand, if a sharing denial message is returned, the flow advances to step S 122 , and the control unit  11  writes information “unit sharing is denied” in the external functional unit column of the configuration management table, and updates the version of the table. 
   If in step S 114  no functional unit to be added to the configuration is found, the flow advances to step S 124 , and the control unit  11  writes information “no unit” in the external functional unit column of the configuration management table, and updates the version of the table. 
   After steps S 120 , S 122 , and S 124  are complete, the flow advances to step S 126  to check whether the configuration management table setting process is completely performed for all usable external functional units. If NO in step S 126 , the flow returns to step S 110 . If YES in step S 126 , the flow returns to step S 52 . 
   If no external functional unit connected to the other control unit  31  is to be added to the configuration, in step S 52 , a configuration list necessary to implement a desired function is formed by combining functional units connected to the control unit  11  across the internal LAN  110 . 
   In this case, some functional units are so set as to be sharable. For example, even if the MFP  1  shown in  FIG. 1  has no FAX unit, FAX data can be directly transmitted from the MFP  1  by adding the FAX unit of the MFP  2  to the configuration. 
   However, a large number of network apparatuses are connected to the external LAN  41  and shared. This makes it difficult to ensure performance when data is transferred across the external LAN  41 . Therefore, the control unit  11  monitors whether predetermined performance is obtained for data transferred to a functional unit connected across the external LAN  41 . If no predetermined performance is obtained, the control unit  11  notifies the manager or the like of a warning message. 
   Even while the system is in operation after the configuration is determined, the control unit  11  monitors whether each functional unit is normally operating. Each functional unit executes self-diagnosis for each predetermined time, even while the unit is not in operation and standing by, and notifies the control unit  11  of the result. 
   If this notification sent from a functional unit to the control unit  11  is an error status or if no notification is sent to the control unit  11  for a predetermined time, the control unit  11  sends a reset command to the corresponding functional unit to check whether the functional unit normally operates. If this functional unit does not normally operate after resetting, the control unit  11  reconfigures the MFP by combining other functional units except this functional unit. The control unit  11  similarly reconfigures the MFP when deleting an operating functional unit from the internal LAN. 
   The procedure of reconfiguration is the same as the flow of determining a configuration after the power supply is turned on. When reconfiguration is thus performed, the operation unit  17  is notified of this information so that the user notices that the configuration is changed. The contents can also be displayed on the operation/display unit  20  to allow the user to know the details of the reconfiguration. 
   Reconfiguration is also performed when a new functional unit is added across the internal LAN  110  to the control unit  11  via the router  12  while the system is in operation. 
   This addition of a functional unit can be performed while the operation continues without turning off the power supply of the whole system. 
   When a new functional unit is added, the number of configurable combinations increases. If the newly added combination has priority over the existing combinations, the priority order is automatically changed. 
   If the control unit  11  cannot automatically change this priority order, the control unit  11  displays or notifies the manager of a message to perform resetting. 
   For example, if no functional unit analogous to a new functional unit exists in the existing combinations, this new functional unit is simply added. If a functional unit similar to a new functional unit exists and these two units can be simultaneously operated in combination, the new functional unit is added to the configuration to improve the performance. If the two functional units cannot be operated at the same time, the new functional unit is used as an auxiliary unit. 
   In step S 54  of  FIG. 7B , whether there is a combination whose priority order is designated by the manager or the like is checked. If such a combination is present as described previously, the flow advances to step S 58  to configure an MFP by the designated combination. If no such combination is present, the flow advances to step S 56  to configure an MFP by using a combination prepared by the manufacturer. 
   In step S 60 , an ID address indicating a configuration number is transmitted to each functional unit used in the configuration. 
   In step S 62 , whether a job exists is checked. If a job exists, this job is executed in step S 66 . This job execution will be described later with reference to  FIG. 11A . 
   If no job exists, this is equivalent to a standby state in which the system does not operate as an MFP. In this standby state, the processing from step S 62  to step S 76  is repeated. In step S 64 , whether a message is sent from a functional unit to the control unit  11  is checked. If there is a message, the message is processed in step S 68 . This message processing will be explained later with reference to  FIG. 11C . 
   In step S 70 , the control unit  11  checks whether a predetermined time has elapsed. If NO in step S 70 , the flow returns to step S 62 . If YES in step S 70 , the flow advances to step S 72 , and the control unit  11  checks whether each functional unit has an error status, non-updated status, or the like. If no such status is present, the flow returns to step S 62 . If such a status is present, the flow advances to step S 74 , and the control unit  11  transmits a reset command to the functional unit which has sent this error status. 
   In step S 76 , the control unit  11  checks whether the functional unit which has transmitted an error status has restored its normal operation by resetting. If the normal operation has not been restored, the flow advances to step S 26  described above. If the normal operation has been restored, the flow advances to step S 62  to continue the standby state. 
   As described above, if a failure occurs in an incorporated functional unit after the MFP system is configured, the control unit  11  gives a reset command to the faulty functional unit to check whether the functional unit normally operates. If the control unit  11  determines that there is an error, the flow returns to step S 26  to reconfigure the MFP system by using other functional units except for the faulty functional unit. 
   The job execution procedure will be described below with reference to  FIGS. 11A to 1C . In this embodiment, the MFP configuration can be dynamically changed so as to minimize the time required to complete each job. 
   As shown in  FIG. 11A , in step S 210 , whether a plurality of functional units having equivalent functions are present and usable is checked. If no plurality of usable functional units are present, the flow advances to step S 218 . If a plurality of usable functional units are present, the flow advances to step S 212 . 
   In step S 212 , whether these functional units can be simultaneously operated is checked. If they cannot be operated at the same time, setting is so performed that one functional unit is used and the remaining functional units are used as backup in the event of a failure, and the flow advances to step S 218 . If these functional units can be simultaneously operated, the flow advances to step S 216 . 
   In step S 216 , a job is divisionally assigned to these functional units. 
   In step S 218 , whether each functional unit normally operates is checked before the job is executed. If the functional unit does not normally operate, the flow returns to step S 210 . If the functional unit normally operates, the flow advances to step S 220 , and the functional unit executes the assigned job. 
   If a functional unit connected to an external network is added to the MFP system configuration, the control unit  11  monitors whether this functional unit satisfies predetermined performance. If it is determined that the functional unit does not satisfy the performance, the control unit  11  may output a warning message to the operation/display unit  20 . 
   On the basis of the contents of individual jobs (Nos. 1, 2, 3, . . . ), e.g., information such as the function classification, the number of originals to be processed, and the number of copies, combinations of functional units necessary to implement the functions shown in  FIG. 8  are referred to, and an optimum combination, i.e., a combination by which the job completion time is minimized is determined for each job. 
     FIG. 12  shows combinations of functional units configured to execute job Nos. 1 to 7. 
   Job Nos. 1 and 2 are executed by the functional unit combination of configuration No. 1. 
     FIG. 13  shows functional units combined as configuration No. 1. That is,  FIG. 13  shows a configuration which presents to the user an image on the display screen of the operation/display unit  20 . 
   As a front end  400  in front of the user, an MFP  11 , ADF units  411  and  421 , scanner units  412  and  422 , image processing units  413  and  423 , data storage  431 , and operation/display unit  432  are combined. 
   As a back end  440  not directly seen by the user, an MFP  12 , RIP (Raster Image Processor) unit  451 , and data storage  452  are combined. 
   To prepare for a failure, an MFP  13 , operation/display unit  471 , and RIP unit  472  exist as an auxiliary  460 . 
   The function classification of job No. 1 is a copier. The number of originals is 50 or more, and the number of copies is 1. Job No. 1 is executed by using the front end  410  of configuration No. 1 shown in  FIG. 13 . 
   The function classification of job No. 2 is printing. The number of originals is 1, and the number of copies is also 1. Job No. 2 is executed by using the back end  440  of configuration No. 1 shown in  FIG. 13 . With these combinations, the completion times of job Nos. 1 and 2 can be minimized. 
   As shown in  FIG. 12 , the functional unit combination must be reconfigured when the operation proceeds from job No. 2 to job No. 3.  FIG. 14  shows a functional unit combination as configuration No. 2. Similar to  FIG. 13 ,  FIG. 14  shows a configuration which presents to the user an image on the display screen of the operation/display unit  20 . 
   As a front end  500 , an ADF unit  511 , scanner unit  512 , image processing unit  513 , and operation/display unit  514  are combined. 
   As a back end  540 , MFPs  21  and  22 , RIP unit  551 , and data storage  552  are combined. 
   As a back end  560 , an MFP  23 , RIP unit  571 , and data storage  572  are combined. 
   As an auxiliary  580 , an ADF unit  591 , scanner unit  592 , image processing unit  593 , and operation/display unit  594  are combined. 
   The function classification of job No. 3 is printing. The number of originals is 10, and the number of copies is 2. Job No. 3 is executed by using the back end  540  of configuration No. 2 shown in  FIG. 14 . 
   The function classification of job No. 4 is printing. The number of originals is 3, and the number of copies is 2. Job No. 4 is executed by using the back end  560  of configuration No. 2. 
   The function classification of job No. 5 is a scanner. Job No. 5 is executed by using the front end  500  of configuration No. 2. 
   The function classification of job No. 6 is printing. The number of originals is 2, and the number of copies is 10. Job No. 6 is executed by using the back end  540  of configuration No. 2. 
   The function classification of job No. 7 is printing. The number of originals is 3, and the number of copies is 1. Job No. 7 is executed by using the back end  560  of configuration No. 2. By using these combinations for the individual jobs, the completion times of job Nos. 3 to 7 can be minimized. 
   When the user selects the number of a job displayed on the screen of the operation/display unit by clicking or the like, the selected execute job information is displayed. To select and execute job No. 3 first, the execute sequence may be changed such that job No. 3 and job Nos. 1 and 2 are switched. 
   In step S 220  shown in  FIG. 11A , the control unit  11  transmits a message in order to designate an operation sequence necessary to execute a job to each functional unit. 
   In step S 222 , the control unit  11  checks whether each functional unit sends a status to show that the functional unit is normal. If NO in step S 222 , the flow advances to steps S 224  and S 226  to transmit a message until the designated number of times of retry is exceeded, and the flow returns to step S 220 . If the functional unit does not send a status even after the designated number of times of retry is exceeded, the flow advances to step S 26  in  FIG. 7A . 
   If the control unit  11  determines in step S 222  that each functional unit sends a status to show that the functional unit is normal, the flow advances to step S 228 . 
   In step S 228 , the control unit  11  subdivides the job and designates execution to a set synchronous point. The synchronous point is a point at which processes by a plurality of functional units must be synchronized. More specifically, when a leading functional unit advances its process to a certain stage while a plurality of functional units are executing subdivided jobs, the whole processing must be temporarily stopped until other succeeding functional units advance their processes to the same stage. This point is the synchronous point. 
   In step S 230 , whether each functional unit sends a status to the control unit  11  to show that the functional unit is normal is checked. If YES in step S 230 , the flow advances to step S 240  shown in  FIG. 11B . If NO in step S 230 , the flow advances to step S 232 . 
   In steps S 232  and S 236 , a message is transmitted until the designated number of times of retry is exceeded, and the flow returns to step S 228 . If the functional unit does not send a status even after the designated number of times of retry is exceeded, the flow advances to step S 234  to abnormally terminate the job and notifies the manager of this abnormal termination. 
   In the flowchart shown in  FIG. 11B , in step S 240 , whether all the synchronous points contained in the job are complete is checked. If all the synchronous points are complete, the job ends in step S 244 . If not all the synchronous points are complete in step S 240 , the flow advances to step S 242 , and the control unit  11  transmits to each functional unit a message indicating execution to the next synchronous point. After that, the flow returns to step S 230  in  FIG. 11A . 
   If the job ends in step S 244 , the flow returns to step S 66  shown in  FIG. 7B . 
   If the message processing is to be executed in step S 68  of  FIG. 7B , the flow advances to  FIG. 11C . In step S 252 , whether the message is sent from a functional unit connected to the internal LAN is checked. If the message is sent from a functional unit connected to the internal LAN, the flow advances to step S 254 . If the message is not sent from a functional unit connected to the internal LAN, the flow advances to step S 258 . 
   In step S 254 , the status management table of the functional unit connected to the internal LAN is updated. In step S 256 , the message processing is complete. 
   If the message is not sent from a functional unit connected to the internal LAN, the flow advances to step S 258  to check whether the message is a functional unit sharing request. If the message is a sharing request, the flow advances to step S 260 ; if not, the flow advances to step S 264 . 
   In step S 260 , whether sharing of the corresponding functional unit is permitted is checked. If sharing is permitted, the flow advances to step S 262 ; if not, the flow advances to step S 264 . 
   In step S 262 , a control unit connected to the external LAN performs setting for sharing this functional unit, and the flow returns to step S 256  in  FIG. 11C . 
   If the message is not a functional unit sharing request of if sharing of the functional unit is not permitted, the flow advances to step S 264 , and the control unit  11  transmits a message indicating denial of sharing of the functional unit to the control unit connected to the external LAN. Then, the flow returns to step S 256  in  FIG. 11C . 
   In the embodiment described above, if an MFP system currently being used includes a reusable unit whose life has not expired yet when the system is to be discarded, this unit can be reused as a constituent element of an MFP system to be newly purchased. That is, the user can freely configure the system. 
   Also, since the degree of freedom of combinations of functional units is high, MFP manufacturers can reduce the number of types of functional units to be developed. 
   When a large number of MFPs are used, labor can be saved by checking the stock of parts in a remote place and automatically ordering necessary parts. 
   Furthermore, it is possible to determine whether parts being used are recommended products. This makes it possible to eliminate poor products which may cause failures, and help improve the system operating ratio. 
   The above embodiment is merely an example and does not limit the present invention, so the present invention can be variously modified within the technical scope of the invention. For example, each functional unit in the above embodiment may also include another functional unit required to configure an MFP system.