Abstract:
A method for controlling an information processing system that includes a client device including a plurality of sensors that acquire positional information of the client device and a server device that transmits data to the client device includes causing the server device to specify a positioning requirement corresponding to positional information of the client device based on association information associating a distance between the client device and a location in which the server device transmits the data to the client device located with each of the sensors, and causing the client device to select a sensor based on the positioning requirement specified by the server device among the sensors.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2012-034577, filed on Feb. 20, 2012, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The embodiments discussed herein are related to a method for controlling an information processing system, a server device and a client device. 
     BACKGROUND 
     In recent years, the number of mobile terminals that include various sensors is increasing. The mobile terminals can use the sensors to sense behaviors of users. The number of services using positional information as sensing information is increasing. For example, there is the following service. That is, the current position of a user is measured by a global positioning system (GPS) installed in a smart phone, a wireless local area network (LAN) or the like. When the user approaches a location (store, station or the like) specified by a service provider, a center server distributes, to a mobile terminal of the user, an application and coupon that can be used at the location. In the service, an application installed in the mobile terminal periodically acquires information of the current position of the mobile terminal from the GPS or the like and transmits the acquired positional information to the center server. The center server determines, on the basis of the received positional information, whether or not the user has entered in a range in which the service is provided. If the user is in the range, the center server distributes an application and recommended information. 
     For mobile terminals, there are multiple positioning methods such as autonomous navigation using a GPS, a wireless LAN, a public mobile phone line, an acceleration sensor and a geomagnetic sensor in order to acquire information of the positions of users. The amounts of power to be consumed by the mobile terminals and the accuracies of the positioning methods vary. In general, when a high-accuracy positioning method is used by a mobile terminal, the amount of power to be consumed by the mobile terminal is large. An application that uses positional information and is executed on a mobile terminal does not detect a range in which a service registered in the mobile terminal is provided. Thus, positional information is acquired using a high-accuracy positioning method at short time intervals and is continuously transmitted to the center server. When positioning is repeated with a high accuracy at short time intervals and positional information is transmitted to the center server, the center server can acquire detailed data of the position of a user. The mobile terminal, however, repeats positioning for a short time and consumes power. When an application of the mobile terminal executes positioning with a low accuracy, and the user is close to the range in which the service is provided, the mobile terminal is detected to be far from the range in which the service is provided. In this case, an application and recommended information may not be distributed. Even when the user is far from the range in which the service is provided, and positioning continues to be executed with a high accuracy, the mobile terminal consumes power. 
     Public mobile phone lines enable mobile terminals to perform communication upon subscriptions to the mobile terminals. Normally, the public mobile phone lines enable the mobile terminals to perform communication in order to receive calls and mails. A service for positioning mobile terminals through the public mobile phone lines is provided. Although the accuracy of the positioning is low, the amount of power to be consumed is small. If the positioning is to be executed with a high accuracy, the positioning is executed using a wireless LAN or a GPS and power is consumed in order to newly drive the sensor. 
     The following is a related-art document. 
     Japanese Laid-open Patent Publication No. 2006-115415 is an example of related art. 
     SUMMARY 
     According to an aspect of the invention, a method for controlling an information processing system that includes a client device including a plurality of sensors that acquire positional information of the client device and a server device that transmits data to the client device includes causing the server device to specify a positioning requirement corresponding to positional information of the client device based on association information associating a distance between the client device and a location in which the server device transmits the data to the client device located with each of the sensors, and causing the client device to select a sensor based on the positioning requirement specified by the server device among the sensors. 
     The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a first diagram illustrating an information processing system; 
         FIG. 2  is a diagram illustrating a hardware configuration of a server; 
         FIG. 3  is a diagram illustrating a hardware configuration of a mobile terminal; 
         FIG. 4  is a second diagram illustrating the information processing system; 
         FIG. 5  is a diagram illustrating a service ID table; 
         FIG. 6  is a diagram illustrating a user ID table; 
         FIG. 7  is a diagram illustrating setting information; 
         FIG. 8  is a first diagram illustrating sensor usage information; 
         FIG. 9  is a diagram illustrating sensor accuracy management information; 
         FIG. 10  is a flowchart of a process that is executed by a sensor adjuster; 
         FIG. 11  is a first diagram illustrating a positioning requirement determination table; 
         FIG. 12  is a second diagram illustrating a positioning requirement determination table; 
         FIG. 13  is a first flowchart of a process that is executed by a positioning requirement determining unit; 
         FIG. 14  is a first flowchart of a process that is executed by the sensor adjuster; 
         FIG. 15  is a second diagram illustrating sensor usage information; 
         FIG. 16  is a second flowchart of a process that is executed by the sensor adjuster; 
         FIG. 17  is a third flowchart of the process that is executed by the sensor adjuster; 
         FIG. 18  is a second flowchart of a process that is executed by the positioning requirement determining unit; 
         FIG. 19  is a fourth flowchart of a process that is executed by the sensor adjuster; 
         FIG. 20  is a first diagram describing effects of an embodiment; 
         FIG. 21  is a second diagram describing effects of the embodiment; and 
         FIG. 22  is a third diagram describing an effect of the embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     Hereinafter, an information processing device according to the first embodiment is described. 
       FIG. 1  is a diagram illustrating the information processing system according to the first embodiment. The information processing system includes a plurality of servers  100 , a network  300  and a mobile terminal  200 . The plurality of servers  100  and the mobile terminal  200  are connected to each other through the network  300 . 
       FIG. 2  is a diagram illustrating a hardware configuration of each of the servers  100  according to the present embodiment. The servers  100  each include a central processing unit (CPU)  101 , a main storage device  102 , a system controller  103 , a bus  104 , a network controller  107 , a power supply  109 , a disk controller  112  and a hard disk  113 . The servers  100  are controlled by the CPUs  101 . 
     The CPU  101  and the main storage device  102  are connected to the system controller  103 . The system controller  103  controls transmission of data between the CPU  101  and the main storage device  102  and transmission of data between the CPU  101  and the bus  104 . The system controller  103  is connected to the network controller  107  and the disk controller  112  through the bus  104 . 
     At least a part of an OS program and an application program is temporarily stored in the main storage device  102 . The OS program and the application program are executed by the CPU  101 . Data of various types that is used for a process to be executed by the CPU  101  is stored in the main storage device  102 . A random access memory (RAM) is used as the main storage device  102 , for example. 
     The disk controller  112  is connected to the hard disk  113  and controls the hard disk  113 . The hard disk  113  stores application programs  1100  and a control program  1000 . The CPU  101  executes the application programs  1100  on the main storage device  102 . The control program  1000  causes the CPU  101  to control calling of the application programs  1100  and the like. The hard disk  113  stores service target positional information, positional information of a user and the like, which are described later. 
     The network controller  107  is connected to the mobile terminal  200  through the network  300  illustrated in  FIG. 1  and transmits and receives data of various types to and from the mobile terminal  200 . The power supply  109  supplies power to each of the hardware parts included in the server  100  through power supply lines (not illustrated). Processing functions of the server  100  can be achieved by the aforementioned hardware. 
       FIG. 3  is a diagram illustrating a hardware configuration of the mobile terminal  200  according to the present embodiment. The mobile terminal  200  illustrated in  FIG. 3  is a smart phone, a tablet personal computer (PC) or the like, for example. 
     The mobile terminal  200  includes a central processing unit (CPU)  201 , a main memory  202 , an auxiliary memory  203 , a clock supply circuit  204 , a voltage supply circuit  205 , a radio frequency (RF) unit  206 , an antenna  207  and a battery  208  as hardware modules. In addition, the mobile terminal  200  includes a power supply circuit  209 , a camera module  210 , a Bluetooth interface  211 , a liquid crystal display (LCD)  213 , sensors  214  and an external power supply unit  215  as hardware modules. The hardware modules are connected to each other through a bus  216 . 
     The CPU  201  controls the whole mobile terminal  200 . The CPU  201  operates on the basis of a clock signal supplied from the clock supply circuit  204  and a voltage supplied from the power supply circuit  205 . The CPU  201  completely stops operating if a software process is not executed. The CPU  201  is in a sleep state until an interrupt is provided from outside the mobile terminal  200 . Thus, the CPU  201  reduces power to be consumed. The CPU  201  may be a quad-core CPU or include an arbitrary number of cores. 
     The main memory  202  is a RAM, for example. The main memory  202  is used as a work area of the CPU  201 . The auxiliary memory  203  is a hard disk or a nonvolatile memory such as a flash memory, for example. The auxiliary memory  203  stores various programs to be used to operate the mobile terminal  200 . The programs stored in the auxiliary memory  203  are loaded into the main memory  202  and executed by the CPU  201 . By causing the CPU  201  to execute the programs, various programs (described later) are executed in the mobile terminal  200 . 
     The clock supply circuit  204  supplies a frequency-variable clock signal to the CPU  201 . The clock supply circuit  204  can be achieved by a crystal oscillator for oscillating the clock signal or a real time clock (RTC), for example. The voltage supply circuit  205  uses power supplied form the power supply circuit  209  and thereby supplies a variable voltage to the CPU  201 . The voltage supply circuit  205  can be achieved by a voltage detector and a voltage regulator, or the like. 
     The RF unit  206  has a function of transmitting a high-frequency signal from the antenna  207  to another wireless communication device. The RF unit  206  is controlled by the CPU  201  and thereby transmits the high-frequency signal. The RF unit  206  has a function of converting a high-frequency signal received by the antenna  207  into a baseband signal and outputting the baseband signal to the CPU  201 . 
     The battery  208  supplies power to the power supply circuit  209 . The battery  208  can be achieved by a battery such as a lithium ion battery and an integrated circuit (IC) for protecting the battery, or the like. The power supply circuit  209  supplies the power supplied from the battery  208  to the hardware modules of the mobile terminal  200  through a power supply line (not illustrated). When the external power supply unit  215  is connected to an external power supply, the power supply circuit  209  may supply power supplied from the external power supply unit  215  to the hardware modules of the mobile terminal  200 . The power supply circuit  209  can be achieved by a switching regulator and a voltage regulator, or the like. 
     The camera module  210  is controlled by the CPU  201 , thereby images an object and acquires video image data obtained by imaging the object. The Bluetooth interface  211  is a communication interface that is controlled by the CPU  201  and thereby uses Bluetooth (registered trademark) to perform wireless communication with another communication device. The mobile terminal  200  may include the Bluetooth interface  211  and a wireless communication interface such as a local area network (LAN) interface. 
     The LCD  213  is an image display device that is controlled by the CPU  201  and thereby displays an image for a user. The LCD  213  may be a touch panel that has a touch pad with a function of receiving positional information. 
     The sensors  214  are controlled by the CPU  201  and thereby acquire information indicating each of states of internal parts of the mobile terminal  200 . Examples of the sensors  214  are an acceleration sensor, a gyrosensor, an illuminance sensor, a geomagnetic sensor, an inclination sensor, a pressure sensor, a proximity sensor, a temperature sensor, 3G, a wireless LAN and a GPS module. The GPS module is controlled by the CPU  201 , thereby receives a radio wave emitted by a satellite and acquires positional information indicating the current position of the mobile terminal  200  on the earth. 
       FIG. 4  is a diagram illustrating the information processing system according to the present embodiment. The information processing system includes the server  100  and the mobile terminal  200 . Functions (described later) of the server  100  are achieved by causing the CPU  101  of the server  100  to execute various programs, while functions (described later) of the mobile terminal  200  are achieved by causing the CPU  201  of the mobile terminal  200  to execute various programs. 
     The server  100  includes a positional information receiver  120 , a service position/user position accumulation database (DB)  122 , a positioning requirement determining unit  124  and a positioning requirement transmitter  126 . The positional information receiver  120  acquires positional information of the mobile terminal  200  from the mobile terminal  200 . The positional information receiver  120  causes the positional information acquired from the mobile terminal  200  and indicating the position of the mobile terminal  200  to be stored in the service position/user position accumulation DB  122 . 
     The service position/user position accumulation DB  122  stores a service ID and information of a location (a station, a store or the like) at which a service is provided. The service ID is identification information that is used in order for a service provider to identify the service. 
       FIG. 5  is a diagram illustrating a service ID table  410 . The service ID table  410  is stored in the service position/user position accumulation DB  122 . The service ID table  410  includes items for a service ID  412  and service target positional information  414 . The service ID  412  is information that identifies a service that is provided by the server  100  to the mobile terminal  200 . The service target positional information  414  is information of the position of the mobile terminal  200  to which the service corresponding to the service ID  412  is provided. 
       FIG. 6  is a diagram illustrating a user ID table  420 . The user ID table  420  is stored in the service position/user position accumulation DB  122 . The user ID table  420  includes items for a user ID  422 , a current position  424  and an acquisition time  426 . The user ID  422  is information that identifies a user to which the server  100  provides a service. The current position  424  indicates the current position of the mobile terminal  200 . The acquisition time  426  indicates a time when the server  100  acquires information of the current position of the corresponding user. 
     The positioning requirement determining unit  124  determines, on the basis of the positional information received from the mobile terminal  200 , positioning requirements that include a frequency at which positional information of the mobile terminal  200  is next acquired and the accuracy of the positional information of the mobile terminal  200 . The positioning requirement determining unit  124  transmits the positioning requirements to the positioning requirement transmitter  126 . It is assumed that the transmitted positioning requirements indicate “a service ID, positioning, the accuracy: low and the frequency: only once”, for example. 
     The positioning requirement transmitter  126  transmits the positioning requirements received from the positioning requirement determining unit  124  to the mobile terminal  200 . 
     The mobile terminal  200  includes a positioning requirement receiver  222 , a sensor adjuster  224 , a sensor accuracy management DB  226 , the sensors  214  and a positional information acquirer  228 . 
     The positioning requirement receiver  222  receives the positioning requirements from the positioning requirement transmitter  126  of the server  100 . The positioning requirement receiver  222  transmits the received positioning requirements to the sensor adjuster  224 . 
     The sensor adjuster  224  references the received positioning requirements. When the sensor adjuster  224  detects that the accuracy is not “high” and the frequency is set to “only once”, the sensor adjuster  224  causes the mobile terminal  200  to execute positioning using a sensor  214  that is indicated in setting information  450  stored in the sensor accuracy management DB  226  and acquires positional information for a short acquisition time period indicated in the setting information  450 . 
       FIG. 7  is a diagram illustrating the setting information  450 . The setting information  450  is stored in the sensor accuracy management DB  226 . The setting information  450  includes items for acquisition time periods  426  and information of sensors  454  to be used. The acquisition time periods  426  indicate time periods for acquisition of positional information. The information of the sensors  454  to be used indicates the names of sensors  214  to be used. 
     In general, if it takes a long time to acquire positional information in positioning, the amount of power to be consumed is large. When the frequency is set to “only once”, it is sufficient if an approximate position is acquired, and the position can be acquired for a short time. Thus, it is efficient to set the frequency to “only once”. Especially, when a base station is used for the positioning, the positioning is executed using a public mobile phone line that is in a communication state. In this case, although the accuracy of the positioning is low, the positioning can be executed for approximately 10 seconds without turning on a power supply for a new device. 
     Power to be consumed by the sensors  214  is described below. In GPS positioning, the mobile phone  200  captures signals from, for example, four GPS satellites and uses the signals to detect the position of the mobile terminal  200 . The mobile terminal  200  calculates distances between the mobile terminal  200  and the GPS satellites on the basis of time periods in which the signals propagate from the GPS satellites to the mobile terminal  200 . The mobile terminal  200  treats, as the position of the mobile terminal  200 , a point at which four spherical surfaces intersect with each other. The mobile terminal  200  receives orbit data (almanac data) of all the GPS satellites and satellite orbit data (ephemeris data). The two types of data is 50 bps and transmitted from the GPS satellites to the mobile terminal  200  at intervals of 30 seconds. 
     It takes 30 seconds or more for the mobile terminal  200  to receive new ephemeris data from the GPS satellites. The mobile terminal  200  searches satellite signals transmitted from GPS satellites and specifies the GPS satellites located above the mobile terminal  200 . Then, the mobile terminal  200  receives the almanac data from the GPS satellites, detects orbits of all the GPS satellites, searches another satellite, and receives ephemeris data. The received ephemeris data has an expiration date. After the expiration date, the mobile terminal  200  receives ephemeris data again. 
     As described above, the mobile terminal  200  captures signals from the GPS satellites, acquires data from the GPS satellites, and executes positioning using time information. Thus, it takes some time to execute the positioning, and the mobile terminal  200  consumes power corresponding to the time period for the positioning. 
     In the base station positioning, the mobile terminal  200  uses positional information (latitude and longitude) of the base station to detect the position of the mobile terminal  200 . Since the notified information is the information of the base station, the accuracy of the base station positioning is low. It is, however, sufficient if the mobile terminal  200  uses 3G that is used for calls and communication. 3G provides a function of accessing the server  100  and thereby acquiring the position of the mobile terminal  200 . 
     The base station positioning enables the position of the mobile terminal  200  to be detected for a short time (several seconds) even when the mobile terminal  200  is indoors or located in a basement or the like. A new sensor is not used for the base station positioning. The base station positioning can be achieved only with power that is used for temporal communication. 
     For the GPS positioning, the GPS sensor (GPS module) is operated. The base station positioning can be achieved using a 3G line that is normally in an ON state. Regarding calculations, the latitude and the longitude are calculated from time information in the GPS positioning. The latitude and the longitude can be acquired in the base station positioning. Regarding operating times, in the GPS positioning, the mobile terminal  200  continuously operates for one minute or more from a state in which the mobile terminal  200  does not have satellite orbit data. In the base station positioning, the mobile terminal  200  operates for several seconds. Thus, in the GPS positioning that causes the mobile terminal  200  to operate for one minute or more, the amount of power to be consumed by the mobile terminal  200  is large. 
     If the positioning requirements received by the sensor adjuster  224  indicate that “a service ID, positioning, the accuracy: middle, and the frequency: an interval of 3 minutes”, an accuracy that is higher than the middle accuracy or a power-on state of the GPS (GPS module) is confirmed. If the GPS is in an ON state due to a request provided for another service, it is wasteful to turn on a wireless LAN of which a positioning accuracy is lower than the GPS. Thus, the positioning is executed by the GPS. If a sensor  214  of which a positioning accuracy is higher than an accuracy indicated in the received positioning requirements and that is in an ON state due to a request provided for another service does not exist, a sensor  214  that matches the accuracy indicated in the received positioning requirements is selected and turned on. Then, the positioning is executed by the selected sensor  214 . Before the positioning is executed, the service ID included in the received positioning requirements is described in an item for usage service IDs  421  in sensor usage information  460 . The mobile terminal  200  transmits the positional information received by executing the positioning to a center server and deletes the service ID from the item for usage service IDs in the sensor usage information  460 . After that, the sensor  214  is turned off on the basis of the frequency described in the positioning requirements until the positioning is next executed. Before the sensor  214  is turned off, the mobile terminal  200  confirms that a service that uses the sensor  214  used is not provided or any service ID does not exist in the item for usage service IDs in the sensor usage information  460 . 
       FIG. 8  is a diagram illustrating the sensor usage information  460 . The sensor usage information  460  is stored in the sensor accuracy management DB  226 . The sensor usage information  460  includes information of the sensors  454  to be used, power supply states  464 , usage service IDs  421  and previous positioning information  468 . The information of the sensors  454  to be used indicates the sensors  214  to be used. The power supply states  464  indicate that power supplies of the corresponding sensors  214  are in ON or OFF states. The usage service IDs  421  indicate IDs to be used by a user. The previous positioning information  468  indicates coordinates, an accuracy, an acquisition time and a positioning time, which are obtained when the positioning is executed using a corresponding sensor  214 . 
     The sensor adjuster  224  references the sensor accuracy management DB  226 , selects a sensor  214  to be operated from among the plurality of sensors  214  on the basis of the positioning requirements received from the positioning requirement receiver  222 , and switches on or off the selected sensor  214 . 
       FIG. 9  is a diagram illustrating sensor accuracy management information  470 . The sensor accuracy management information  470  is stored in the sensor accuracy management DB  226 . The sensor accuracy management information  470  includes items for positioning accuracies  472 , current sensor information  474  and consumption power  476 . The positioning accuracies  472  indicate the accuracies of the positioning to be executed by the corresponding sensors  214 . The current sensor information  474  indicates the types of the current sensors  214 . The consumption power  476  indicates power to be consumed by the corresponding sensors  214 . The sensor accuracy management information  470  is updated on the basis of the positioning accuracies as illustrated in  FIG. 9 . The update of the sensor accuracy management information  470  is described later. 
     Relationships between the sensors  214  and power to be consumed by the sensors  214  are described below. In order to detect the position of the mobile terminal  200 , signals are captured from GPS satellites (for example, four GPS satellites) by the mobile terminal  200  and used by the mobile terminal  200  in the GPS positioning. The mobile terminal  200  calculates distances between the mobile terminal  200  and the GPS satellites on the basis of time periods in which the signals propagate from the GPS satellites to the mobile terminal  200 . The mobile terminal  200  treats, as the position of the mobile terminal  200 , a point at which four spherical surfaces intersect with each other. The mobile terminal  200  receives orbit data (almanac data) of all the GPS satellites and satellite orbit data (ephemeris data). The two types of data is 50 bps and transmitted from the GPS satellites to the mobile terminal  200  at intervals of 30 seconds. 
     It takes 30 seconds or more for the mobile terminal  200  to receive new ephemeris data from the GPS satellites. The mobile terminal  200  searches satellite signals transmitted from GPS satellites and specifies the GPS satellites located above the mobile terminal  200 . Then, the mobile terminal  200  receives the almanac data from the GPS satellites, detects orbits of all the GPS satellites, searches another satellite, and receives ephemeris data. The received ephemeris data has an expiration date. After the expiration date, the mobile terminal  200  receives ephemeris data again. 
     As described above, the mobile terminal  200  captures signals from the GPS satellites, acquires data from the GPS satellites, and executes positioning using time information. It takes some time to execute the positioning, and the mobile terminal  200  consumes power corresponding to the time period for the positioning. 
     In the base station positioning, the mobile terminal  200  uses positional information (latitude and longitude) of the base station to detect the position of the mobile terminal  200 . Since the notified information is the information of the base station, the accuracy is low. It is, however, sufficient if the mobile terminal  200  uses 3G that is used for calls and communication. 3G provides a function of accessing the server  100  and thereby acquiring the position of the mobile terminal  200 . 
     The base station positioning enables the position of the mobile terminal  200  to be acquired for a short time (several seconds) even when the mobile terminal  200  is indoors or located in a basement or the like. A new sensor is not used for the base station positioning. The base station positioning can be achieved only with power that is used for temporal communication. 
     For the GPS positioning, the GPS sensor is operated. The base station positioning can be achieved by a 3G line that is normally in an ON state. Regarding calculations, the latitude and the longitude are calculated from time information in the GPS positioning. The latitude and the longitude can be acquired in the base station positioning. Regarding operating times, in the GPS positioning, the mobile terminal  200  continuously operates for one minute or more from the state in which the mobile terminal  200  does not have satellite orbit data. In the base station positioning, the mobile terminal  200  operates for several seconds. Thus, in the GPS positioning that causes the mobile terminal  200  to operate for one minute or more, the amount of power to be consumed by the mobile terminal  200  is large. 
       FIG. 10  is a flowchart of a process that is executed by the sensor adjuster  224 . 
     In S 001 , the sensor adjuster  224  acquires positional information from any of the sensors  214 . The sensor adjuster  224  causes the process to proceed to S 002 . 
     In S 002 , the sensor adjuster  224  extracts an accuracy of the positional information. The sensor adjuster  224  causes the process to proceed to S 003 . 
     In S 003 , the sensor adjuster  224  replaces the positioning accuracies and sensor types of the sensor accuracy management information  470  so as to update the sensor accuracy management information  470 . The sensor adjuster  224  causes the process to proceed to S 004 . 
     In S 004 , the sensor adjuster  224  transmits the acquired positional information to the positional information acquirer  226 . The sensor adjuster  224  terminates the process. 
     The positional information transmitted by the mobile terminal  200  is received by the positional information receiver  120  of the server  100  as described above, and is stored in the service position/user position accumulation DB  122  as a user ID, a current position and an acquisition time. The positioning requirement determining unit  124  determines the next position requirements on the basis of the received positional information. For example, the positioning requirement determining unit  124  determines positioning requirements on the basis of a service target position stored in the service position/user position accumulation DB  122  and information indicating the position of a user and stored in the service position/user position accumulation DB  122 . 
       FIG. 11  illustrates a positioning requirement determination table  430 . The positioning requirement determination table  430  is stored in the service position/user position accumulation DB  122 . The positioning requirement determination table  430  includes items for distances  432 , setting accuracies  434  and setting frequencies  436 . The distances  432  indicate distances between the mobile terminal  200  and locations at which a service is provided. The setting accuracies  434  indicate the positioning accuracies of the sensors  214  that are used by the mobile terminal  200  to measure the position of the mobile terminal  200 . The setting frequencies  436  indicate frequencies at which the mobile terminal  200  measures the position of the mobile terminal  200 . The positioning requirement determination table  430  stores the distances  432 , the setting accuracies  434  and the setting frequencies  436  while a distance  432 , a setting accuracy  434  and a setting frequency  436  that are described in each of rows of the positioning requirement determination table  430  are associated with each other. 
     The positioning requirement determining unit  124  references the positioning requirement determination table  430  and determines positioning requirements on the basis of the information received from the positional information receiver  120  and indicating the position of the mobile terminal  200 . The positioning requirement determining unit  124  sets positioning requirements on the basis of a distance between the received current position (P1) of the mobile terminal and a service target position (P0). When d(x, y) indicates a distance between x and y, the positioning requirement determining unit  124  determines positioning requirements corresponding to a value of d(P1, P0) on the basis of the positioning requirement determination table  430  (illustrated in  FIG. 11 ) in a step-by-step manner. 
     For example, the positioning requirement determining unit  124  determines positioning requirements on the basis of whether or not the mobile terminal  200  relatively approaches the service target position. 
       FIG. 12  illustrates a positioning requirement determination table  530 . The positioning requirement determination table  530  is stored in the service position/user position accumulation DB  122 . The positioning requirement determination table  530  includes items for positioning requirement levels  442 , setting accuracies  434  and setting frequencies  436 . The positioning requirement levels  442  indicate levels of positioning requirements. The setting accuracies  434  indicate positioning accuracies of the sensors  214  that are used by the mobile terminal  200  to measure the position of the mobile terminal  200 . The setting frequencies  436  indicate frequencies at which the mobile terminal  200  measures the position of the mobile terminal  200 . The positioning requirement determination table  530  stores the positioning requirement levels  442 , the setting accuracies  434  and the setting frequencies  436 , while a positioning requirement level  442 , a setting accuracy  434  and a setting frequency  436  that are described in each of rows of the positioning requirement determination table  530  are associated with each other. 
     If a previously acquired position of the mobile terminal  200  is indicated by P2, and d(P2, P0)&gt;d(P1, P0), the positioning requirement determining unit  124  determines positioning requirements on the basis of the positioning requirement determination table  530  (illustrated in  FIG. 12 ) while increasing the positioning requirement level one by one. 
       FIG. 13  is a flowchart of a process that is executed by the positioning requirement determining unit  124 . 
     In S 101 , the positioning requirement determining unit  124  receives positional information of the mobile terminal  200  from the positional information receiver  120 . The positioning requirement determining unit  124  causes the process to proceed to S 102 . 
     In S 102 , the positioning requirement determining unit  124  causes the positional information, received from the positional information receiver  120 , of the mobile terminal  200  to be stored in the service position/user position accumulation DB  122 . The positioning requirement determining unit  124  causes the process to proceed to S 103 . 
     In S 103 , the positioning requirement determining unit  124  references the positioning requirement determination table  430  or  530  and determines positioning requirements on the basis of a distance between the position, indicated in the positional information received from the positional information receiver  120 , of the mobile terminal  200  and a location at which a service for transmitting data is provided. The positioning requirement determining unit  124  causes the process to proceed to S 104 . 
     In S 104 , the positioning requirement determining unit  124  determines whether or not previous positioning requirements are changed to the determined positioning requirements. If the previous positioning requirements are changed to the determined positioning requirements, the positioning requirement determining unit  124  causes the process to proceed to S 105 . If the previous positioning requirements are not changed to the determined positioning requirements, the positioning requirement determining unit  124  causes the process to return to S 101 . If the previous positioning requirements are changed to the determined positioning requirements, the positioning requirement determining unit  124  can transmit the latest transmission requirement to the mobile terminal  200 . 
     In S 105 , the positioning requirement determining unit  124  transmits the determined positioning requirements to the positioning requirement transmitter  126 . The positioning requirement determining unit  124  causes the process to return to S 101 . 
       FIG. 14  is a flowchart of a process that is executed by the sensor adjuster  224 . 
     In S 201 , the sensor adjuster  224  receives the positioning requirements. The sensor adjuster  224  causes the process to proceed to S 202 . 
     In S 202 , the sensor adjuster  224  determines whether or not the positioning requirements indicate that “the accuracy is not “high” and the frequency is “only once””. If the positioning requirements indicate that “the accuracy is not “high” and the frequency is “only once””, the sensor adjuster  224  causes the process to proceed to S 203 . If the positioning requirements do not indicate that “the accuracy is not “high” and the frequency is “only once””, the sensor adjuster  224  causes the process to proceed to S 204 . 
     In S 203 , the sensor adjuster  224  references the setting information  450  and selects a sensor  214  corresponding to a “short acquisition time period”. The sensor adjuster  224  causes the process to proceed to S 207 . 
     In S 204 , the sensor adjuster  224  references the positioning requirements and determines whether or not a power supply of a sensor  214  of which a positioning accuracy is higher than the requested accuracy is in an ON state. If the power supply of the sensor  214  of which the positioning accuracy is higher than the requested accuracy is in the ON state, the sensor adjuster  224  causes the process to proceed to S 205 . If the power supply of the sensor  214  of which the positioning accuracy is higher than the requested accuracy is not in the ON state, the sensor adjuster  224  causes the process to proceed to S 206 . 
     In S 205 , the sensor adjuster  224  selects the sensor  214  of which the positioning accuracy is higher than the requested accuracy and of which the power supply is in the ON state. The sensor adjuster  224  causes the process to proceed to S 207 . 
     In S 206 , the sensor adjuster  224  references the positioning requirements and selects a sensor  214  of which a positioning accuracy is the same as the requested accuracy. The sensor adjuster  224  causes the process to proceed to S 207 . 
     In S 207 , the sensor adjuster  224  turns on the power supply of the selected sensor  214  if the power supply of the selected sensor  214  is not in the ON state, and the sensor adjuster  224  adds a service ID to the sensor usage information  460 . The sensor adjuster  224  causes the process to proceed to S 208 . 
     In S 208 , the sensor adjuster  224  acquires positional information from the selected sensor  214 . The sensor adjuster  224  causes the process to proceed to S 209 . 
     In S 209 , the sensor adjuster  224  transmits the acquired positional information to the positional information acquirer  228 . The sensor adjuster  224  causes the process to proceed to S 210 . 
     In S 210 , the sensor adjuster  224  deletes the service ID from the sensor usage information  460 . The sensor adjuster  224  causes the process to proceed to S 211 . 
     In S 211 , the sensor adjuster  224  determines whether or not the sensor  214  is unused for another service. If the sensor  214  is unused for the other service, the sensor adjuster  224  causes the process to proceed to S 212 . If the sensor  214  is used for the other service, the sensor adjuster  224  causes the process to proceed to S 213 . 
     In S 212 , the sensor adjuster  224  turns off the power supply of the sensor  214 . The sensor adjuster  224  causes the process to proceed to S 213 . 
     In S 213 , the sensor adjuster  224  causes the sensor  214  selected on the basis of the positioning requirements to be in a sleep state for a set time. The sensor adjuster  224  causes the process to proceed to S 204 . 
     According to the present embodiment, the positioning requirement determining unit  124  of the service  100  determines positioning requirements including a frequency at which positional information of the mobile terminal  200  is next acquired and the accuracy of the positional information of the mobile terminal  200 . Then, the positioning requirement determining unit  124  transmits the determined positioning requirements to the positioning requirement transmitter  126 . The positioning requirement receiver  222  of the mobile terminal  200  receives the positioning requirements and transmits the positioning requirements to the sensor adjuster  224 . The sensor adjuster  224  references the sensor accuracy management DB  226  and selects a sensor  214  matching the positioning accuracy included in the received positioning requirements. The sensor adjuster  224  turns on the sensor  214  of which a positioning accuracy matches the positioning requirements. Then, the sensor adjuster  224  causes the sensor  214  to execute the positioning. The mobile terminal  200  transmits positional information acquired by the positioning to the center server. After that, the sensor adjuster  224  turns off the sensor  214  on the basis of the positioning frequency described in the positioning requirements until the positioning is next executed. The higher the accuracy of the positioning, the larger the amount of power to be consumed. Thus, if the positioning requirement (accuracy) transmitted from the center server is low, a sensor  214  of which a positioning accuracy is low (and that consumes a small amount of power) is used. The sensor  214  that is used by the mobile terminal  200  is changed on the basis of positioning requirements that vary depending on whether or not high-accuracy positional information is to be used. Thus, it is effective to save power to be consumed by the mobile terminal  200 . 
     According to the present embodiment, a frequency at which positional information of the mobile terminal  200  is acquired and the accuracy of the positional information of the mobile terminal  200  are determined on the basis of a distance between the current position of the user and a service target position. Thus, if the user is far from the service target position, the accuracy of the positioning is reduced and the frequency of the positioning is reduced so that an interval between times of the positioning is increased. Thus, the amount of power to be consumed by the mobile terminal  200  can be reduced. On the other hand, if the user approaches the service target position, the accuracy of the positioning is increased and the frequency of the positioning is increased so that an interval between times of the positioning is reduced. Thus, an accurate position of the user can be detected, and whereby the quality of the service is improved. High-accuracy positioning is not executed in some cases. A reduction in the amount of power to be consumed by the mobile terminal  200  can be achieved by temporarily reducing a positioning accuracy to be requested and a frequency of positioning. 
     Second Embodiment 
     The sensor accuracy management DB  226  of the mobile terminal  200  according to the second embodiment holds, as the sensor usage information  460 , a time period for a certain sensor  214  to acquire the position of the mobile terminal  200 . If a sensor  214  does not acquire the position of the mobile terminal  200  within a time period that is equal to a period of time for the sensor  214  to previously acquire the position of the mobile terminal  200 , the mobile terminal  200  determines not to receive a sufficient radio wave, sets a positioning accuracy of the sensor executing the positioning to “low”, and relatively increases positioning accuracies of the other sensors  214 . 
       FIG. 15  illustrates sensor usage information  480  according to the present embodiment. The sensor usage information  480  includes items for information of sensors  454  to be used, states  464  of power supplies, service IDs  421  and previous positioning information  468 . The previous positioning information  468  includes positioning time periods that are periods of times to acquire the position of the mobile terminal  200  in the positioning. 
     For example, as illustrated in  FIG. 9 , the sensor accuracy management information  470  that indicates that the positioning accuracy of the public mobile phone line&lt;the positioning accuracy of the wireless LAN&lt;the positioning accuracy of the GPS/IMES is updated to the sensor accuracy management information  470  that indicates that the positioning accuracy of the GPS/IMES&lt;the positioning accuracy of the public mobile phone line&lt;the positioning accuracy of the wireless LAN. This assumes that the user enters in a building or the like, the mobile terminal  200  does not receive a signal with a sufficient intensity from a GPS satellite, and the positioning accuracy of the GPS/IMES actually becomes lower than the positioning accuracy of the public mobile phone line. The GPS positioning is not limited to the case where the user is indoors. When the GPS positioning is used and the user enters in a shadow of a building or the like, the number of GPS satellites that transmit signals that can be received by the mobile terminal  200  may be reduced and the positioning accuracy may be reduced. Thus, it is possible to avoid using a sensor  214  that does not ensure a high accuracy (or consumes a large amount of power). 
     The positioning using the public mobile phone line can be achieved regardless of whether the user stays indoors or outdoors. Thus, a problem that if the positioning accuracy of the GPS/IMES is set to “low”, the positioning accuracy GPS/IMES is not changed from “low” occurs. To avoid this problem, a positioning time is described in the sensor usage information  460 . The sensor adjuster  224  receives positioning requirements before selecting a sensor  214  to be operated from among the plurality of sensors  214 . If a time threshold elapses after the positioning time, the positioning is executed in accordance with a default setting (for example, the positioning accuracy of the public mobile phone line&lt;the positioning accuracy of the wireless LAN&lt;the positioning accuracy of the GPS/IMES). The sensor adjuster  224  confirms the current validity of the sensor accuracy management DB  226  on the basis of a positioning accuracy included in received positional information. If the sensor adjuster  224  acquires the positional information that indicates a higher positioning accuracy than the low positioning accuracy, the sensor adjuster  224  replaces the positioning accuracies so as to update the sensor accuracy management information  470 . 
       FIGS. 16 and 17  are flowcharts of a process that is executed by the sensor adjuster  224 . 
     In S 301 , the sensor adjuster  224  acquires positioning requirements. The sensor adjuster  224  causes the process to proceed to S 302 . 
     In S 302 , the sensor adjuster  224  determines whether or not the positioning requirements indicate that “the accuracy is not “high” and the frequency is “only once””. If the positioning requirements indicate that “the accuracy is not “high” and the frequency is “only once””, the sensor adjuster  224  causes the process to proceed to S 303 . If the positioning requirements do not indicate that “the accuracy is not “high” and the frequency is “only once””, the sensor adjuster  224  causes the process to proceed to S 304 . 
     In S 303 , the sensor adjuster  224  references the setting information  450  and selects a sensor  214  corresponding to a “short acquisition time period”. The sensor adjuster  224  causes the process to proceed to S 310 . 
     In S 304 , the sensor adjuster  224  references the positioning requirements and determines whether or not a power supply of a sensor  214  of which a positioning accuracy is higher than a requested accuracy is in the ON state. If the power supply of the sensor  214  of which the positioning accuracy is higher than the requested accuracy is in the ON state, the sensor adjuster  224  causes the process to proceed to S 305 . If the power supply of the sensor  214  of which the positioning accuracy is higher than the requested accuracy is not in the ON state, the sensor adjuster  224  causes the process to proceed to S 306 . 
     In S 305 , the sensor adjuster  224  selects the sensor  214  of which the power supply is in the ON state and of which the positioning accuracy is higher than the requested accuracy. The sensor adjuster  224  causes the process to proceed to S 307 . 
     In S 306 , the sensor adjuster  224  references the positioning requirements and selects a sensor  214  of which a positioning accuracy is the same as the requested accuracy. The sensor adjuster  224  causes the process to proceed to S 307 . 
     In S 307 , the sensor adjuster  224  acquires, from the sensor usage information  480 , a positioning time (T1) of the previous positioning information for the selected sensor  214 . The sensor adjuster  224  causes the process to proceed to S 308 . 
     In S 308 , the sensor adjuster  224  determines whether or not a time threshold elapses after the positioning time T1. If the time threshold elapses after the positioning time T1, the sensor adjuster  224  causes the process to proceed to S 309 . If the time threshold does not elapse after the positioning time T1, the sensor adjuster  224  causes the process to proceed to S 310 . 
     In S 309 , the sensor adjuster  224  selects a sensor  214  in accordance with the default for the requested accuracy. The sensor adjuster  224  causes the process to proceed to S 310 . 
     In S 310 , if the power supply of the selected sensor  214  is not in the ON state, the sensor adjuster  224  turns on the power supply of the selected sensor  214  and adds a service ID to the sensor usage information  480 . The sensor adjuster  224  causes the process to proceed to S 311  illustrated in  FIG. 17 . 
     In S 311 , the sensor adjuster  224  acquires positional information from the sensor  214 . The sensor adjuster  224  causes the process to proceed to S 312 . 
     In S 312 , the sensor adjuster  224  transmits the acquired positional information to the positional information acquirer  228 . The sensor adjuster  224  causes the process to proceed to S 313 . 
     In S 313 , the sensor adjuster  224  deletes the service ID from the sensor usage information  480 . The sensor adjuster  224  causes the process to proceed to S 314 . 
     In S 314 , the sensor adjuster  224  determines whether or not the sensor  214  is unused for another service. If the sensor  214  is unused for the other service, the sensor adjuster  224  causes the process to proceed to S 315 . If the sensor  214  is used for the other service, the sensor adjuster  224  causes the process to proceed to S 316 . 
     In S 315 , the sensor adjuster  224  turns off the power supply of the sensor  214 . The sensor adjuster  224  causes the process to proceed to S 316 . 
     In S 316 , the sensor adjuster  224  causes the selected sensor  214  to be in a sleep state for a set time. The sensor adjuster  224  causes the process to return to S 304  illustrated in  FIG. 16 . 
     According to the present embodiment, the sensor usage information  480  holds a period of time to acquire the position of the mobile terminal  200  in the positioning. If a sensor  214  does not acquire the position of the mobile terminal  200  within a time period that is equal to a time period for the sensor  214  to previously acquire the position of the mobile terminal  200 , the mobile terminal  200  determines not to receive a sufficient radio wave, sets a positioning accuracy of a sensor  214  executing the positioning to “low”, and relatively increases positioning accuracies of the other sensors  214 . For example, if the positioning accuracy of the GPS is set to “high”, the information processing system normally operates, and the user enters in a building or the like, the mobile terminal  200  may not receive a signal with a sufficient intensity from a GPS satellite, and the accuracy of the GPS positioning may become lower than the accuracy of the base station positioning. The mobile terminal  200  can accurately respond to an accuracy request transmitted from the server  100 . In addition, the information processing system can inhibit the mobile terminal  200  from executing positioning and thereby continuously acquiring low-accuracy data while consuming a large amount of power, even when the mobile terminal  200  is located in a building or the like and does not accurately receive a signal from a GPS satellite. If the positioning accuracy of the GPS is set to “low”, information of the positioning accuracy of the GPS is stored in the sensor information management DB  226 , and the mobile terminal  200  receives positioning requirements indicating that the accuracy is “low”, the GPS that consumes a large amount of power is to be operated. However, the sensor  214  (public mobile phone line) of which the positioning accuracy is higher than the requested accuracy is in the ON state. Thus, the public mobile phone line is prioritized. 
     According to the present embodiment, the sensor usage information  480  holds a time to execute the positioning. When the mobile terminal  200  receives, from another server, positioning requirements that indicates that the accuracy of the positioning is “low” and the frequency of the positioning is “only once”, the mobile terminal  200  does not turn on a sensor  214  matching the positioning requirements in order to execute the positioning. If the difference between the held positioning time and the current time is equal to or smaller than a certain threshold, the mobile terminal  200  can transmit previously acquired positioning data to the server instead of acquiring new positioning data. Thus, the mobile terminal  200  does not newly execute the positioning and can reduce the amount of power to be consumed. 
     According to the present embodiment, a time to previously execute the positioning is held. Thus, if the sensor adjuster  224  determines that the positioning accuracy of the GPS is “low”, and a certain time threshold elapses, the mobile terminal  200  executes the positioning in accordance with the default values (for example, the positioning accuracy of the public mobile phone line&lt;the positioning accuracy of the wireless LAN&lt;the positioning accuracy of the GPS) and confirms the validity of the sensor accuracy management DB  226 . Thus, even if the sensor adjuster  224  determines that the positioning accuracy of the GPS is lower than the positioning accuracy of the public mobile phone line, and the user moves to an outdoor location, the sensor adjuster  224  rechecks the relationships between the positioning accuracies and the sensors  214 . The sensor adjuster  224  causes the GPS to operate in accordance with the default values when the positioning accuracy of the GPS is “high”. The sensor adjuster  224  can accurately update the sensor accuracy management DB  226  on the basis of a time to execute the positioning and the positioning accuracy of the GPS. 
     Third Embodiment 
     In the aforementioned embodiments, the positioning requirement determination tables  430  and  530  are stored in the service position/user position accumulation DB  122 . For example, the positioning requirement determination tables  430  and  530  may be stored in the sensor accuracy management DB  226  and the mobile terminal  200  may determine positioning accuracies (to be set) and frequencies (to be set) on the basis of information, transmitted from the server  100 , of a distance between the mobile terminal  200  and a location at which a service is provided. 
       FIG. 18  is a flowchart of a process that is executed by the positioning requirement determining unit  124 . 
     In S 401 , the positioning requirement determining unit  124  receives positional information of the mobile terminal  200  from the positional information receiver  120 . The positioning requirement determining unit  124  causes the process to proceed to S 402 . 
     In S 402 , the positioning requirement determining unit  124  causes the positional information, received from the positional information receiver  120 , of the mobile terminal  200  to be stored in the service position/user position accumulation DB  122 . The positioning requirement determining unit  124  causes the process to proceed to S 403 . 
     In S 403 , the positioning requirement determining unit  124  calculates, on the basis of the positional information (of the mobile terminal  200 ) received from the positional information receiver  120 , a distance between the mobile terminal  200  and a location at which a service for transmitting data is provided. The positioning requirement determining unit  124  causes the process to proceed to S 404 . 
     In S 404 , the positioning requirement determining unit  124  transmits information (distance information) of the calculated distance to the positioning requirement transmitter  126 . The positioning requirement determining unit  124  causes the process to return to S 401 . 
       FIG. 19  is a flowchart of a process that is executed by the sensor adjuster  224 . 
     In S 501 , the sensor adjuster  224  acquires the distance information. The sensor adjuster  224  causes the process to proceed to S 502 . 
     In S 502 , the sensor adjuster  224  references the positioning requirement determination table  430  or  530 , determines positioning requirements on the basis of the acquired distance information, and determines whether or not the determined positioning requirements indicate that “the accuracy is not “high” and the frequency is “only once””. If the determined positioning requirements indicate that “the accuracy is not “high” and the frequency is “only once””, the sensor adjuster  224  causes the process to proceed to S 503 . If the determined positioning requirements do not indicate that “the accuracy is not “high” and the frequency is “only once””, the sensor adjuster  224  causes the process to proceed to S 504 . 
     In S 503 , the sensor adjuster  224  references the setting information  450  and selects a sensor  214  corresponding to a “short acquisition time period”. The sensor adjuster  224  causes the process to proceed to S 507 . 
     In S 504 , the sensor adjuster  224  references the positioning requirements and determines whether or not a power supply of a sensor  214  of which a positioning accuracy is higher than a requested accuracy is in the ON state. If the power supply of the sensor  214  of which the positioning accuracy is higher than the requested accuracy is in the ON state, the sensor adjuster  224  causes the process to proceed to S 505 . If the power supply of the sensor  214  of which the positioning accuracy is higher than the requested accuracy is not in the ON state, the sensor adjuster  224  causes the process to proceed to S 506 . 
     In S 505 , the sensor adjuster  224  selects the sensor  214  of which the power supply is in the ON state and of which the positioning accuracy is higher than the requested accuracy. The sensor adjuster  224  causes the process to proceed to S 507 . 
     In S 506 , the sensor adjuster  224  references the positioning requirements and selects a sensor  214  of which a positioning accuracy is the same as the requested accuracy. The sensor adjuster  224  causes the process to proceed to S 507 . 
     In S 507 , if the power supply of the selected sensor  214  is not in the ON state, the sensor adjuster  224  turns on the power supply of the selected sensor  214  and adds a service ID to the sensor usage information  460 . The sensor adjuster  224  causes the process to proceed to S 508 . 
     In S 508 , the sensor adjuster  224  acquires positional information from the selected sensor  214 . The sensor adjuster  224  causes the process to proceed to S 509 . 
     In S 509 , the sensor adjuster  224  transmits the acquired positional information to the positional information acquirer  228 . The sensor adjuster  224  causes the process to proceed to S 510 . 
     In S 510 , the sensor adjuster  224  deletes the service ID from the sensor usage information  460 . The sensor adjuster  224  causes the process to proceed to S 511 . 
     In S 511 , the sensor adjuster  224  determines whether or not the sensor  214  is unused for another service. If the sensor  214  is unused for the other service, the sensor adjuster  224  causes the process to proceed to S 512 . If the sensor  214  is used for the other service, the sensor adjuster  224  causes the process to proceed to S 513 . 
     In S 512 , the sensor adjuster  224  turns off the power supply of the sensor. The sensor adjuster  224  causes the process to proceed to S 513 . 
     In S 513 , the sensor adjuster  224  causes the sensor  214  selected on the basis of the positioning requirements to be in a sleep state for a set time. The sensor adjuster  224  causes the process to return to S 504 . 
     According to the present embodiment, the positioning requirement determining unit  124  of the server  100  calculates a distance between the position of the mobile terminal  200  and a location at which a service is provided. Then, the positioning requirement transmitter  126  transmits information (distance information) of the calculated distance to the mobile terminal  200 . The positioning requirement receiver  222  of the mobile terminal  200  receives the distance information. The positioning requirement receiver  222  determines positioning requirements on the basis of the received distance information and transmits the determined positioning requirements to the sensor adjuster  224 . The sensor adjuster  224  references the sensor accuracy management DB  226  and selects a sensor  214  matching a positioning accuracy included in the received positioning requirements. The sensor adjuster  224  turns on the sensor  214  of which the positioning accuracy matches the positioning requirements. Then, the mobile terminal  200  executes the positioning. The mobile terminal  200  transmits positional information acquired by the positioning to the center server. After that, the sensor  214  is turned off on the basis of the frequency described in the positioning requirements until the positioning is next executed. The higher the accuracy of the positioning, the larger the amount of power to be consumed. Thus, if the positioning requirement (accuracy) transmitted from the center server is low, a low-accuracy sensor (consuming a small amount of power)  214  is used. The sensor  214  that is used by the mobile terminal  200  is changed on the basis of positioning requirements that vary depending on whether or not high-accuracy positional information is requested. Thus, it is effective to save power to be consumed by the mobile terminal  200 . 
       FIG. 20  is a diagram illustrating effects of the present embodiment. According to the present embodiment, if a detail of a request provided for a service indicates that a positioning accuracy is “low”, the mobile terminal  200  uses a power-saving sensor  214 . An interval between times of the positioning can be increased on the basis of a detail (frequency) of the request provided for the service. If the number of GPS satellites transmitting signals that can be used for positioning is small, or positional information and the accuracy of the positional information are known, the difference between a measured position and the actual position is large, and the positioning requirement determining unit  124  can make a determination, for example, can determine that the mobile terminal  200  is sufficiently far from a service target range or the like, the result of the positioning is sufficient. In this case, a process that is repeated to cause a measured value to converge to a certain value is not executed. If a requested accuracy is low, the base station positioning can be executed, and a period of time to execute the positioning once can be reduced. 
       FIG. 21  is a diagram illustrating effects of the present embodiment. If the relationships between the positioning accuracies and the sensors  214  are fixed, a large amount of power is consumed and the accuracy of the positioning is low. According to the present embodiment, however, power can be saved and the accuracy of the positioning is high. 
       FIG. 22  is a diagram illustrating an effect of the present embodiment. According to the present embodiment, when positioning requirements are set from the plurality of servers, the relationships between the sensors  214  and currently provided positioning accuracies are updated by the sensor accuracy management DB. Thus, an appropriate positioning result can be provided. 
     The information processing system according to the embodiments is described. The information processing system, however, is not limited to the embodiments disclosed herein and may be variously modified and changed without departing from the scope of the claims. For example, when the sensor usage information  480  holds a time to execute positioning and the mobile terminal  200  receives, from another server, positioning requirements that indicate that the positioning accuracy is “low” and the frequency of the positioning is “only once”, the mobile terminal  200  does not turn on a sensor  214  matching the positioning requirements and execute positioning, and can transmit previously acquired positioning data to the server if the difference between the held time to execute the positioning and the current time is equal to or smaller than a threshold. In this case, even if the frequency of the positioning indicates an “interval of 5 minutes”, previously acquired positioning data may be transmitted in the first positioning, and the positioning may be executed after 5 minutes. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.