Abstract:
A system comprising a wireless tag and a tag reader. The tag comprises: a sensor for generating a detected information; a storage for storing the detected information; a determination unit for storing a criteria information and outputting a result of determination on the detected information on the basis of the criteria information; and a communication control unit for transmitting the determination result in response to receiving a request. The reader transmits the request to the tag and receives the determination result from the tag.

Description:
[0001]     This application claims priority to prior Japanese patent application JP 2005-126277, the disclosure of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a wireless tag capable of acquiring information detected by a built-in sensor, a wireless tag reader/writer, a wireless tag information provision method, and a wireless tag system.  
         [0004]     2. Description of the Related Art  
         [0005]     Along with development of information communication technology, the trend has set in to perform commodity management or to streamline the commodity information display or the commodity distribution by packaging a Radio Frequency (RF) tag having an integrated circuit with memory [generally, sometimes called as electronic tag, contactless data carrier, wireless IC tag, contactless IC, contactless IC label, contactless IC tag, RFID (Radio Frequency Identification) or NFC (Near Field Communication) tag] in articles and recording various types of information in the RF tag. The RF tag performs wireless communication with a RF tag reader device which reads information such as an identification code stored in the memory incorporated in the RF tag. Hereafter, the RF tag shall be referred to as “wireless tag”.  
         [0006]     Wireless tags having various types of built-in sensors have recently been drawing attention. The wireless tags with built-in sensors are employed in various systems. As an example of such systems, a perishable food management system suitable for characteristics and distribution mode of perishable foods has been proposed (see Japanese Laid-Open Patent Publication No. 2002-358591, paragraphs 0058-0060 (hereafter, Patent Publication 1), for example).  
         [0007]     The system described in Patent Publication 1 is a system for managing preservation quality when storing and transporting perishable foods. According to this system, a tag includes a temperature sensor for detecting temperature, an impact sensor for detecting impact, a memory for storing data detected by the temperature and impact sensors, a transceiver for transmitting the data in the form of extremely low radio waves, and an identification number adding portion for adding an identification number unique to the tag to the data, and such tag is enclosed in a package containing perishable foods. A tag receiver for receiving data transmitted from the tag is installed in the vicinity of the place where the package is stored, and the tag receiver is connected to communication equipment which utilizes a communication circuit or wide area wireless networks. An information collection center is installed for collecting data on the tags from the communication equipment. The information collection center determines the preservation quality of the perishable food in each package based on a history of preservation environment indicated by the collected tag data, and informs the preservation quality to a terminal which makes an inquiry to the information collection center via a communication circuit Preservation environment determination means is further provided at least in any of the tag, a transport vehicle, and the information collection center for determining whether the preservation environment is good or not based on the data detected by the sensors in comparison with a predetermined threshold, and informing the determination result to the transport vehicle transporting the tag.  
         [0008]     In addition to this conventional system, there have been proposed temperature sensors, temperature measurement devices, temperature measurement systems and programs utilizing a wireless tag having a rewritable mass data storage area (see Japanese Laid-Open Patent Publication No. 2004-144683, paragraphs 0017-0018 (hereafter, Patent Publication 2), for example).  
         [0009]     A temperature sensor described in Patent Publication 2 is configured as a wireless tag having a resonant circuit the resonant frequency of which varies depending on temperature. The resonant circuit is composed of a coil and a capacitor. A material the dielectric constant of which varies according to variation in temperature is provided between electrodes of the capacitor. The wireless tag has a memory, communication means, and a microcomputer. The memory stores resonant frequency versus temperature characteristics of the resonant circuit as a table. The microcomputer transmits and receives radio waves via the communication means while changing the frequency to specify a resonant frequency of the resonant circuit, and specifies temperature corresponding to the resonant frequency by referring to the table. The microcomputer periodically specifies the resonant frequency and the temperature, and records the temperatures thus specified in the memory as a history. The microcomputer retrieves the temperature history stored in the memory in response to a command received via the communication means, and transmits the same via the communication means. The temperature measurement device described in Patent Publication 2 includes detection means for detecting a resonant frequency of the resonant circuit by transmitting and receiving radio waves to and from a wireless tag having a resonant circuit the resonant frequency of which varies depending on temperature, specifying means for specifying temperature of the wireless tag based on the detected resonant frequency, receiving means for receiving settings of monitoring temperature by the user, control means for controlling the detection means and the specifying means to periodically specify the temperature, determination means for determining whether or not the specified temperature has reached the monitoring temperature, and alarm means generating an alarm when it is determined that the specified temperature has reached the monitoring temperature.  
         [0010]     There has also been proposed an electronic tag system which is able to shorten the processing time by periodically transmitting transmission information to record history information in a plurality of electronic tags, while simultaneously causing the system&#39;s internal information to be processed in parallel (see Japanese Laid-Open Patent Publication No. 2005-25240, paragraphs 0070-0075 (hereafter, Patent Publication 3), for example).  
         [0011]     An electronic tag system described in Patent Publication 3 has a contactless electronic tag and a reader/writer for contactless electronic tags. The reader/writer includes common accessing means for accessing a plurality of contactless electronic tags in common, and means for transmitting information to the contactless electronic tags with the use of the common accessing means. The contactless electronic tag has means for receiving information provided by the common accessing means, computation means, storage means, and means for transmitting a response to the reader/writer or means for storing the computation result of the computation means in storage means. The computation means includes means for determining a response by using the information provided by the common accessing means and the information stored in the storage means.  
       SUMMARY OF THE INVENTION  
       [0012]     According to the system described in Patent Publication 1, the information collection center is required to receive all the data detected by the sensors for determining whether the preservation environment is good or not. This induces a problem that it takes a long time to retrieve the data if the volume of the data detected by the sensors is large. When a large volume of data has to be retrieved from a wireless tag having built-in sensors, in particular, a battery incorporated in the wireless tag is consumed quickly, which shortens the product life of the wireless tag.  
         [0013]     According to Patent Publication 2, the temperature measurement device has determination means for determining whether or not the specified temperature has reached the monitoring temperature, while the wireless tag has no determination means. Therefore, the temperature measurement device is required to retrieve all the temperature history data held by the wireless tag before implementing the determination. This induces a problem that it takes a long time to read the data if a volume of the temperature history data is large.  
         [0014]     According to the Patent Publication 3, no sensor is incorporated in the system. Therefore, the system is unable to read or determine about data that varies all the time, for example, data of temperature around the wireless tag or temperature of the commodity to which the wireless tag is attached. Additionally, the information that is referred to for making determination is information that is transmitted by the common accessing means when requesting the data stored in the wireless tag. Therefore, if different types of information are to be referred to for different types of commodities, the types of information transmitted by the common accessing means are increased along with the increase of the types of commodities. This induces a problem that it takes a long time to process data when the data is requested.  
         [0015]     It is therefore an object of the present invention to provide a novel wireless tag having built-in sensors, a wireless tag reader/writer, a wireless tag information provision method, and a wireless tag system which are capable of reducing the amount of data read by the wireless tag reader/writer to shorten the communication time and to enable quick data acquisition.  
         [0016]     As an aspect of the present invention, a wireless tag wirelessly communicating with a wireless tag reader/writer, comprising: a sensor for detecting physical stimulus in and/or around the wireless tag to generate a detected information set; a first storage for storing the detected information set; a determination unit for storing a criteria information set and outputting a determination result information set indicating a result of determination on the detected information set on the basis of the criteria information set; and a communication control unit for transmitting the determination result information set output by the determination unit to the wireless tag reader/writer is provided. This aspect allows the wireless tag to transmit to the wireless tag reader/writer the determination result information instead of the detected information. Therefore, transmission quantity from the tag to the reader can be reduced.  
         [0017]     The first storage may store the detected information set according to the determination result information set corresponding to the detected information. According to this configuration, the first storage is able to store only the data that has been determined to be either normal or abnormal, and thus the used storage area can be reduced.  
         [0018]     The communication control unit may transmit to the wireless tag reader/writer at least one of a detected information set and a determination result information set according to the determination result information set corresponding to the transmitted information set(s). According to this configuration, the detected information and/or the determination result information may be transmitted only when the corresponding determination result has a predetermined value. Therefore, transmission quantity from the tag to the reader can be reduced.  
         [0019]     The first storage may store a time information set indicating time at which a detected information is detected, in association with the detected information set. In this case, the communication control unit may transmit to the wireless tag reader/writer the time information set and at least one of the detected information set and the corresponding determination result information set. This configuration allows the reader device to obtain time change of the detected information and determination result information. It is particularly effective when the wireless tag transmits determination result information with a predetermined value such as abnormal or corresponding detected information. According to this configuration, the wireless tag reader/writer is able to acquire only the data that has been determined to be either normal or abnormal as the determination result without requesting all the detected information of the wireless tag.  
         [0020]     In response to receiving a request for at least one of a detected information set and a determination result information set from the wireless tag reader/writer, the communication control unit may transmit the requested information set(s) to the wireless tag reader/writer. According to this configuration, the wireless tag reader/writer is only required to communicate with the wireless tag on the as-needed basis if the reading of the determination result information is not always required. This enables the flexible arrangement of the wireless tag reader/writer.  
         [0021]     The wireless tag may further comprise a second storage for storing the determination result information set. In this case, in response to receiving a request for the determination result information set from the wireless tag reader/writer, the communication control unit may transmit the determination result information set stored in the second storage. According to this configuration, it is made possible to shorten the time period from when the wireless tag reader/writer transmits determination result request information until it receives a determination result, and thus the determination result can be ascertained even more quickly.  
         [0022]     The communication control unit may receive another criteria information set from the wireless tag reader/writer. In this case, the determination unit may update the criteria information set to the other criteria information set. According to this configuration, the reader device can update criteria information stored in the wireless tag.  
         [0023]     As another aspect of the present invention, a wireless tag reader/writer wirelessly communicating with a wireless tag having a detection unit for detecting information on the wireless tag itself and the area surrounding the wireless tag, wherein the wireless tag reader/writer transmits an information set to request the wireless tag for a determination result information set indicating a result of determination on the detected information set on the basis of a criteria information set is provided.  
         [0024]     The wireless tag reader/writer may transmit an information set to request the wireless tag for the detected information.  
         [0025]     The wireless tag reader/writer may further transmit a criteria information set to the wireless tag.  
         [0026]     As another aspect of the present invention, a method of transmitting a information set from a wireless tag to a wireless tag reader/writer, comprising the steps of: detecting physical stimulus in and/or around the wireless tag to generate a detected information set by a sensor of the wireless tag; storing the detected information set to a storage of the wireless tag; evaluating, at the wireless tag, the detected information set on the basis of a criteria information set, which is previously transmitted to the wireless tag, to generate a determination result information set; and transmitting the determination result information set from the wireless tag to the wireless tag reader/writer is provided.  
         [0027]     As another aspect of the present invention, a wireless tag system comprising a wireless tag and a wireless tag reader/writer that wirelessly communicating with the wireless tag is provided. In this system, the wireless tag comprises: a sensor for detecting physical stimulus in and/or around the wireless tag to generate a detected information set; a first storage for storing the detected information set; a determination unit for storing a criteria information set and outputting a determination result information set indicating a result of determination on the detected information set on the basis of the criteria information set; and a communication control unit for transmitting the determination result information set output by the determination unit in response to receiving a request for the determination result information set. The wireless tag reader/writer transmits the request to the wireless tag and receives the determination result information from the wireless tag.  
         [0028]     According to the present invention, a wireless tag having built-in sensors is provided with a determination unit so that the wireless tag is able determine whether sensor data is normal or not. The wireless tag is also able to store the sensor data. Since the wireless tag has the determination unit, there is no need of transmitting all the data from the wireless tag. This makes it possible to shorten the communication time and to ascertain the determination result quickly. Also, the wireless tag reader/writer is able to acquire only the data that has been determined to be normal or abnormal as a determination result without requesting all the detected information from the wireless tag. The detected information storage unit is able to store only the data that has been determined to be normal or abnormal, and thus the used storage area can be reduced. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]      FIG. 1  is a block diagram illustrating a first embodiment of a wireless tag system according to the present invention;  
         [0030]      FIG. 2  is a sequence diagram illustrating operation of the wireless tag system of the first embodiment;  
         [0031]      FIG. 3  is a block diagram illustrating a second embodiment of a wireless tag system according to the present invention; and  
         [0032]      FIG. 4  is a sequence diagram illustrating operation of the wireless tag system of the second embodiment. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     First Embodiment  
       [0033]     A first embodiment of the present invention will now be described with reference to the accompanying drawings.  FIG. 1  is a block diagram illustrating a first embodiment of a wireless tag system according the present invention. The wireless tag system shown in  FIG. 1  includes a wireless tag  100 , a wireless tag reader/writer  200 , and a wireless tag reader/writer  300 .  
         [0034]     The wireless tag  100  includes a sensor  101 , a sensor data storage unit  102 , a transceiver  103 , and a determination unit  104 . The wireless tag  100  further includes a CPU (not shown) operating according to a program and a storage device (not shown) storing the program. Functions of the wireless tag  100  are carried out by the CPU executing the program designed to perform the functions.  
         [0035]     The sensor  101  is for detecting a physical amount such as temperature or pressure, and detects such data relating to the area surrounding the wireless tag and a commodity to which the wireless tag is attached. The sensor data storage unit  102  is for example a storage medium such as a nonvolatile memory, and stores the data detected by the sensor  101 .  
         [0036]     The transceiver  103  has a built-in antenna function, and has a function of performing processing to transmit/receive a wireless signal to/from the wireless tag reader/writers  200  and  300 . The transceiver  103  performs processing to output criteria data received from the wireless tag reader/writer  200  or a determination result request received from the wireless tag reader/writer  300  to the determination unit  104 , and processing to transmit information such as data stored in the sensor data storage unit  102  or a determination result output by the determination unit  104  to the wireless tag reader/writers  200  and  300 .  
         [0037]     The determination unit  104  has a function of performing processing to determine whether or not the data stored in the sensor data storage unit  102  is normal based on the criteria data output by the wireless tag reader/writer  200 , and to output the determination result. The determination result may be information indicating whether or not the stored data contains data determined abnormal (abnormal data). For example, when the sensor data consists of only one item, the information may indicate whether the data is normal or abnormal only. When the sensor data consists of a plurality of items, the information may indicate that the data is normal if all the data items are normal, and indicate that the data is abnormal if any one of the data items is abnormal. The determination unit  104  is embodied by the CPU in the wireless tag  100  executing the program designed to perform the function thereof.  
         [0038]     The wireless tag reader/writer  200  wirelessly communicates with the wireless tag  100 , and has a function of performing processing to transmit criteria data, that is used for determining whether the data stored in the sensor data storage unit  102  is abnormal or not, to the transceiver  103 .  
         [0039]     The wireless tag reader/writer  300  also wirelessly communicates with the wireless tag  100 , and has a function of performing processing to transmit to the transceiver  103  a determination result request requesting a determination result output by the determination unit  104 , and to receive the determination result from the transceiver  103 . The wireless tag reader/writer  300  further has a function of performing processing to transmit to the transceiver  103  a sensor data request requesting the sensor data stored in the sensor data storage unit  102  and to receive the sensor data from the transceiver  103 .  
         [0040]     In the first embodiment, a detection unit is embodied by the sensor  101 . A detected information storage unit is embodied by the sensor data storage unit  102 . A determination unit is embodied by the determination unit  104 . A communication control unit is embodied by the transceiver  103 . A determination result requesting unit and a detected information requesting unit are embodied by the CPU in the wireless tag reader/writer  300  executing a program designed to perform the functions thereof.  
         [0041]     Operation of the first embodiment will now be described with reference to  FIG. 2 .  FIG. 2  is a sequence diagram illustrating the operation of the wireless tag system according to the first embodiment. In the sequence diagram of  FIG. 2 , the solid-line arrows denote requests, and the broken-line arrows denote responses. The following description will be made in terms of an example in which the sensor  101  is a temperature sensor, the criteria data transmitted by the wireless tag reader/writer  200  is set such that the data is determined normal if the temperature is zero degrees or higher and lower than 30 degrees, and the determination result is information indicating whether the data contains abnormal data or not.  
         [0042]     The wireless tag reader/writer  200  transmits the criteria data to the transceiver  103  of the wireless tag  100  (step S 1 ). The transceiver  103  outputs the received criteria data to the determination unit  104  (step S 2 ). The determination unit  104  stores the received criteria data or updates a current criteria data to the received one.  
         [0043]     The sensor  101  measures temperature around the wireless tag and of a commodity to which the wireless tag is attached (step S 3 ), and stores the measurement data in the sensor data storage unit  102  as sensor data (step S 4 ). The processing steps of step S 3  and step S 4  are repeated whereby the sensor data history is stored in the sensor data storage unit  102 .  
         [0044]     The wireless tag reader/writer  300  transmits a determination result request to the transceiver  103  of the wireless tag  100  (step S 5 ). The transceiver  103  outputs the received determination result request to the determination unit  104  (step S 6 ).  
         [0045]     The determination unit  104  requests the sensor data stored in the sensor data storage unit  102  (step S 7 ), and acquire the same (step S 8 ). The determination unit  104  determines, based on the criteria data, that the sensor data is normal if the temperature is zero degrees or higher and lower than 30 degrees, whereas determines that the sensor data is abnormal if the temperature is lower than zero degrees or 30 degrees or higher (step S 9 ).  
         [0046]     The determination unit  104  outputs the determination result to the transceiver  103  (step S 10 ). The transceiver  103  transmits the determination result to the wireless tag reader/writer  300  (step S 11 ).  
         [0047]     In addition to the determination result, the wireless tag reader/writer  300  is also able to request the sensor data from the wireless tag  100  if required. In this case, the wireless tag reader/writer  300  transmits a sensor data request to the transceiver  103  of the wireless tag  100  (step S 12 ). The transceiver  103  requests the sensor data stored in the sensor data storage unit  102  (step S 13 ), and acquires the same (step S 14 ). The transceiver  103  then transmits the sensor data to the wireless tag reader/writer  300  (step S 15 ).  
         [0048]     According to the first embodiment as described above, the wireless tag with a built-in sensor has a determination unit so that the wireless tag is able to determine whether or not the sensor data is normal. This means that the wireless tag reader/writer is not required to make the determination and hence it is not necessary to transmit the entire sensor data stored in the wireless tag to the wireless tag reader/writer. Consequently, it is made possible to shorten the period of time required for data communication between the wireless tag and the wireless tag reader/writer and to quickly ascertain the determination result indicating whether the sensor data is normal or not. When the first embodiment is applied to a commodity distribution system, for example, the processing speed can be improved when a commodity bearing a wireless tag passes through a check point provided with the wireless tag reader/writer. When the wireless tag has a battery incorporated therein so as to use the battery power for data transmission, the power consumed for reading the data can be reduced and hence the product life of the wireless tag can be increased.  
         [0049]     Since the wireless tag is able to store the sensor data, the wireless tag reader/writer has only to communicate with the wireless tag on the as-needed basis if it is not required to read the data constantly. This makes it possible to arrange the wireless tag reader/writer more flexibly.  
         [0050]     Further, the wireless tag is able to store criteria data according to the type of the commodity or the type of the sensor. Therefore, even if the types of the commodities to which the wireless tag is attached or the types of the sensors mounted in the wireless tag are increased, the wireless tag reader/writer is not required to select which criteria are to be used for which wireless tag. Accordingly, such increase will not affect the processing time to request the data or to read the data.  
       Second Embodiment  
       [0051]     A second embodiment of the present invention will now be described with reference to the drawings.  FIG. 3  is a block diagram illustrating a wireless tag system according to the second embodiment of the present invention. A wireless tag system shown in  FIG. 3  includes a wireless tag  100 , a wireless tag reader/writer  200 , and a wireless tag reader/writer  300 .  
         [0052]     The wireless tag  100  includes a sensor  101 , a sensor data storage unit  102 , a transceiver  103 , a determination unit  104 , and a determination result storage unit  105 . The wireless tag  100  further includes a CPU operating according to a program and a storage device storing the program. Functions of the wireless tag  100  are implemented by the CPU executing the program designed to perform the functions.  
         [0053]     The determination result storage unit  105  is a storage area for storing a determination result output by the determination unit  104 . In other aspects, the configuration of the wireless tag system is similar to that of the first embodiment (see  FIG. 1 ), and the description thereof is omitted.  
         [0054]     In the second embodiment, a determination result storage unit is embodied by the determination result storage unit  105 .  
         [0055]     Operation of the second embodiment will now be described with reference to  FIG. 4 .  FIG. 4  is a sequence diagram illustrating the operation of the wireless tag system according to the second embodiment. In the sequence diagram of  FIG. 4 , the solid-line arrows denote requests, while the broken-line arrows denote responses. The following description will be made in terms of an example in which the sensor  101  is a temperature sensor, the criteria data transmitted by the wireless tag reader/writer  200  is set such that the data is determined normal if the temperature is zero degrees or higher and lower than 30 degrees, and the determination result is information indicating whether the data contains abnormal data or not.  
         [0056]     The wireless tag reader/writer  200  transmits the criteria data to the transceiver  103  of the wireless tag  100  (step S 21 ). The transceiver  103  outputs the received criteria data to the determination unit  104  (step S 22 ).  
         [0057]     The sensor  101  measures temperature around the wireless tag and of a commodity to which the wireless tag is attached (step S 23 ), and stores the measurement data in the sensor data storage unit  102  as sensor data (step S 24 ). The processing steps of step  823  and step S 24  are repeated, whereby the sensor data history is stored in the sensor data storage unit  102 . The sensor  101  outputs information indicating that the sensor data has been stored to the determination unit  104  (step S 25 ).  
         [0058]     The determination unit  104  requests the sensor data stored in the sensor data storage unit  102  when required (step S 26 ), and acquires the same (step S 27 ). The determination unit  104  determines, based on the criteria data, that the sensor data is normal if the temperature is zero degrees or higher and lower than 30 degrees, whereas determines that the sensor data is abnormal if the temperature is lower than zero degrees or 30 degrees or higher (step S 28 ). The determination unit  104  stores the determination result in the determination result storage unit  105  (step S 29 ).  
         [0059]     The wireless tag reader/writer  300  transmits a determination result request to the transceiver  103  of the wireless tag  100  (step S 30 ). In response to the received determination result request, the transceiver  103  requests the determination result to the determination result storage unit  105  (step S 31 ), and acquires the determination result (step S 32 ). The transceiver  103  transmits the determination result to the wireless tag reader/writer  300  (step S 33 ).  
         [0060]     Alternatively, the system may be designed such that, when the wireless tag reader/writer  300  transmits a determination result request to the transceiver  103  of the wireless tag  100 , the transceiver  103  outputs the determination result request to the determination unit  10 , and the determination unit  104  requests and acquires the sensor data stored in the sensor data storage unit  102 , determines whether the sensor data is normal or not based on the criteria data, and stores the determination result in the determination result storage unit  105 . The transceiver  103  then requests the determination result storage unit  105  for the determination result, acquires the same, and transmits the determination result thus acquired to the wireless tag reader/writer  300 .  
         [0061]     According to the second embodiment as described above, the determination unit  104  outputs a determination result on the as-needed basis, and the determination result storage unit  105  stores the determination result. Accordingly, in addition to the advantageous effects provided by the first embodiment, the second embodiment further provides an advantageous effect that the period of time from when the wireless tag reader/writer  300  transmits a determination result request until it receives the determination result can be shortened and hence the determination result can be ascertained even more quickly.  
       Third Embodiment  
       [0062]     The description of the embodiments above has been made in terms of an example in which the determination result output by the determination unit  104  is information indicating whether or not abnormal data is contained in the sensor data. However, the determination result may be information containing abnormal data or a time at which the abnormal data is detected. Further, the determination result may be information containing abnormal data and a time at which the abnormal data is detected.  
         [0063]     A description will now be made of a third embodiment of the present invention relating to a case in which information of the determination result contains abnormal data and a time at which the abnormal data is detected. System configuration of the third embodiment is similar to that of the first embodiment (see  FIG. 1 ) and hence the description thereof will be omitted.  
         [0064]     The sensor  101  stores detected data and detected time thereof in association with each other in the sensor data storage unit  102  as sensor data. The determination unit  104  acquires the sensor data stored in the sensor data storage unit  102 .  
         [0065]     The determination unit  104  makes determination on the sensor data based on the criteria data, and outputs, as a determination result, information indicating whether or not the sensor data contains abnormal data and information containing the abnormal data and a time at which the abnormal data is detected, to the wireless tag reader/writer  300  via the transceiver  103 .  
         [0066]     In addition to the advantageous effects provided by the first embodiment, the third embodiment as described above provides a further advantageous effect in that the wireless tag reader/writer  300  is able to acquire only the abnormal data as the determination result without requesting all the sensor data from the wireless tag  100   s . Accordingly, in comparison with the case of requesting all the sensor data, the period of time required for data communication between the wireless tag and the wireless tag reader/writer can be shortened. This means that the result determined to be abnormal can be ascertained more quickly.  
         [0067]     Third embodiment may be combined with the second embodiment.  
       Four Embodiment  
       [0068]     The description of the embodiments above has been made in terms of an example in which the sensor data storage unit  102  stores all the data detected by the sensor  101 . However, the sensor data storage unit  102  may store only abnormal data.  
         [0069]     A description will now be made of a fourth embodiment of the present invention in which the sensor data storage unit  102  stores only abnormal data. The system configuration of the fourth embodiment is similar to that of the second embodiment (see  FIG. 3 ) and hence the description thereof will be omitted.  
         [0070]     The sensor  101  outputs data obtained by measurement to the determination unit  104  as sensor data. The determination unit  104  makes determination on the sensor data based on the criteria data, and stores only abnormal data in the sensor data storage unit  102 . Repeating these processing steps, the abnormal data history is stored in the sensor data storage unit  102 . The determination unit  104  stores the determination result in the determination result storage unit  105 .  
         [0071]     According to the fourth embodiment as described above, the determination unit  104  outputs a determination result when required and the determination result storage unit  105  stores the determination result, while the sensor data storage unit  102  stores only abnormal data. This enables the determination result to be ascertained more quickly. Additionally, the storage area used by the sensor data storage unit  102  can be reduced. Further, the sensor data storage unit  102  is able to store a larger volume of sensor data.  
         [0072]     The fourth embodiment may be combined with the first embodiment and the third embodiment.  
         [0073]     The description of the embodiments above has been made in terms of a case in which the sensor  110  is a temperature sensor. However, the present invention is not limited to this, and the sensor may be, for example, a humidity sensor, an illuminance sensor, an ultraviolet sensor, a carbon dioxide sensor, an impact sensor, and other biological sensor or chemical sensor. Also, although the description has been made in terms of a case in which the wireless tag  100  has a single sensor built in, the wireless tag  100  may have a plurality of sensors built in and may have a plurality of types of sensors together. The description above has been made in terms of a case in which the criteria data transmitted by the wireless tag reader/writer  200  is set such that the sensor data is determined to be normal when the temperature is zero degrees or higher and lower than 30 degrees. However, the criteria data may be set such that the sensor data is determined to be normal (or abnormal) when the measurement value is out of a specified range, or when the rate of change of the measurement value is less than or higher than a specified value. The determination unit  104  may perform determination on the basis of combination of several types of criteria data.  
         [0074]     Although the above description has been made in terms of a case in which the wireless tag  100  transmits a determination result in response to a determination result request transmitted by the wireless tag reader/writer  300 , the wireless tag  100  may transmit a determination result automatically at constant intervals.  
         [0075]     Further, the description of the embodiments above has been made in terms of an example in which the determination unit  104  determines whether the sensor data indicating information on the area surrounding the wireless tag or the commodity to which the wireless tag is attached is normal or not based on the criteria data. However, the determination unit  104  may make determination on the sensor data and a time at which the sensor data is detected. For example, the determination may be made on a difference T 1 -T 0  between a detection time T 1  at which sensor data D 1  is detected and a detection time T 0  at which sensor data D 0  is detected one cycle before the sensor data D 1 , while the criteria data may be set such that the sensor data is determined to be abnormal when the difference between the detection times is greater than the detecting cycle T of the sensor data. In this case, the determination can be made whether the sensor operates normally or not.  
         [0076]     The present invention is applicable for acquiring information detected by sensors and, particularly, is effectively applicable for shortening the communication time for acquisition of the information.