Abstract:
A retrieval tree data storing unit configured to store node information corresponding to the relationship between information configuring data to be retrieved and information of a lower layer configuring the data rather than the information and retrieval tree data corresponding to entity identification information for identifying entity data representing an entity of the data to be retrieved which is specified by the information or the lower information included in the node information; an input controlling unit configured to output a candidate of the data to be retrieved based on the information or the lower information inputted by a user and the node information stored in the retrieval tree data unit; and an entity data acquiring unit configured to transmit to the retrieval server device a retrieval request including the entity identification information corresponding to the information or the lower information included in the candidate of the data to be retrieved.

Description:
CLAIM OF PRIORITY 
       [0001]    The present application claims priority from Japanese application serial no. JP2011-250774, filed on Nov. 16, 2011, the content of which is hereby incorporated by reference into this application. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to a technology that reduces the size of retrieval data. 
       BACKGROUND OF THE INVENTION 
       [0003]    A car navigation system (hereinafter, referred to as a car navigation) provides traffic guide information to a user by processing map data. Models using a hard disk drive (HDD) as recording means of the map data are prevalent in the related art, but in recent years, models using a semiconductor device memory such as an SD memory card or a solid state drive (SSD) have become mainstream. 
         [0004]    The semiconductor device memory has advantages in that power consumption is lower and impact-resistance is larger, but has a disadvantage in that a price per capacity is higher, than the HDD in the related art. As a result, in order to provide the car navigation to the user in the same price range as the related art, the capacity of the used semiconductor device memory needs to be smaller. However, a content of data required for an operation of the car navigation is not changed even though a recording medium is the HDD or the semiconductor device memory, and further, since the size of a database tends to increase every year due to maintenance, etc. of new roads or facilities, the technology of reducing the size of data recorded in the car navigation has been required at all times. As means of reducing the data size, the following technology is proposed. 
         [0005]    First, as means generally used to reduce the data size without changing the content of the data, a data compression technology disclosed in Japanese Unexamined Patent Application Publication No. Hei 8 (1996)-237138 is used. Since the data compression technology can easily reduce the data size, multiple compression methods have been proposed and have widely spread, in addition to the technology disclosed in Japanese Unexamined Patent Application Publication No. Hei 8 (1996)-237138. 
         [0006]    Further, as an additional technology of reducing the size of the data recorded in the car navigation, a technology disclosed in Japanese Unexamined Patent Application Publication No. 2003-207354 is used. In the technology, the data stored in the car navigation in the related art is stored in a server device connected through a communication network, and required data is sequentially downloaded from the server device to perform navigation. Since the data does not need to be stored in the car navigation by the technology, the capacity of the recording medium of the car navigation can be significantly reduced. 
         [0007]    Further, as an additional technology of reducing the size of the data recorded in the car navigation, a technology disclosed in Japanese Unexamined Patent Application Publication No. 2001-304874 is used. In this technology, when retrieval is performed while information on newly maintained roads or stores after selling the car navigation is stored in the database of the server device connected through the communication network, in the case where the database in the car navigation is first retrieved and the corresponding facility is not discovered in the database within the car navigation, input retrieval conditions (genre, telephone numbers, names in alphabetical order) are transmitted to the server device and retrieval is performed in the database of the server device. When this technology is used, since the information on the newly maintained roads or stores need not be recorded in the car navigation after selling the car navigation, the capacity of the recording medium of the car navigation is enough if a capacity to record the database at the time of selling the car navigation is provided, and an increase in the size of the database by the maintained roads or facilities does not need to be considered after selling the car navigation. 
       SUMMARY OF THE INVENTION 
       [0008]    However, the technologies disclosed in Japanese Unexamined Patent Application Publication Nos. Hei 8 (1996)-237138, 2003-207354, and 2001-304874 have the following problems. 
         [0009]    First, in the data compression technology disclosed in Japanese Unexamined Patent Application Publication No. Hei 8 (1996)-237138, processing (hereinafter, referred to as decompressing) to return compressed data to an original state is required before referring to data. Since decompressing takes time, when the data is just compressed, performance when various navigations are performed by referring to the data deteriorates. 
         [0010]    Further, in the technology disclosed in Japanese Unexamined Patent Application Publication No. 2003-207354, processing of acquiring data from the server device through the communication network is required before referring to data. With recent development of a data communication technology, a data communication speed is improved, but there is a problem when communication processing exerts significant influence on a user&#39;s operability. As one example in which the communication processing greatly influences the user&#39;s operability, there is a function to retrieve addresses or facilities by inputting names. When data is retrieved by inputting the names in a general car navigation, whenever one character is input from a keyboard, a candidate name or the corresponding number is displayed, or a control to press only a key which is inputtable next is performed, in order to improve the user&#39;s operability. Since the processing is implemented by acquiring information from a retrieval database whenever one character is input, communication with the server device through the communication network occurs whenever one character is input, and in particular, in a device in which the communication means such as the car navigation is only low-speed mobile communication, the user&#39;s operability significantly deteriorates. 
         [0011]    Further, in the technology disclosed in Japanese Unexamined Patent Application Publication No. 2001-304874, when data is retrieved, the database stored in the car navigation is first retrieved, and when the corresponding data is not provided in the database of the car navigation, the input retrieval conditions (genres, telephone numbers, names in alphabetical order, and the like) are transmitted to the server device and retrieval intends to be performed with the database of the server device, and this technology assumes that an inquiry on the database does not occur while a user inputs the retrieval conditions. However, as described above, a function to present the candidate name to the user whenever one character is input is difficult to be implemented by the technology disclosed in Japanese Unexamined Patent Application Publication No. 2001-304874 because an inquiry on the database inevitably occurs whenever one character is input. 
         [0012]    By considering the above aspect, an object of the present invention is to reduce the size of the database stored in the car navigation without damaging the user&#39;s operability during retrieval operation. 
         [0013]    According to an aspect of the present invention, there is provided a retrieval terminal device connected to a retrieval server device through a communication network, including: a retrieval tree data storing unit configured to store node information corresponding to the relationship between information configuring data to be retrieved and information of a lower layer configuring the data than the information and retrieval tree data corresponding to entity identification information for identifying entity data representing an entity of the data to be retrieved which is specified by the information or the lower information included in the node information; an input controlling unit configured to output a candidate of the data to be retrieved based on the information or the lower information inputted by a user and the node information stored in the retrieval tree data unit; and an entity data acquiring unit configured to transmit to the retrieval server device a retrieval request including the entity identification information corresponding to the information or the lower information included in the candidate of the data to be retrieved, which is output by the input controlling unit and acquire the entity data identified by the entity identification information from the retrieval server device. 
         [0014]    According to another aspect of the present invention, there is provided a retrieval server device receiving a retrieval request of data to be retrieved from a retrieval terminal device through a communication network, including: an entity data storing unit configured to store a plurality of entity identification information pieces for identifying entity data representing an entity of the data to be retrieved and the entity data which correspond to each other; and an entity data managing unit configured to retrieve the data to be retrieved from a plurality of entity data pieces stored in the entity data storing unit based on entity identification information for identifying the data to be retrieved which is specified by node information and lower information included in node information corresponding the relationship between the information configuring the data to be retrieved and the lower information configuring the data than the information and the number of candidates of the data to be retrieved which is specified by the information included in the node information or the lower information, which is included in the retrieval request. 
         [0015]    According to yet another aspect of the present invention, there is provided a retrieval tree compressing method of compressing retrieval tree data, including: a node information listing step of listing a plurality of node information pieces corresponding to the relationship between information configuring data to be retrieved and lower information configuring the data than the information in a predetermined order; a node information classifying step of classifying the plurality of node information pieces listed by the node information listing step into two or more groups; and a node information compressing step of performing different data compression processing or uncompression processing to two or more respective groups classified in the node information classifying step, respectively. 
         [0016]    According to still another aspect of the present invention, there is provided a center-linked retrieval system in which a retrieval terminal device and a retrieval server device are connected to each other through a communication network to retrieve data to be retrieved, in which the retrieval device includes: a retrieval tree data storing unit configured to store node information corresponding to the relationship between information configuring data to be retrieved and information of a lower layer configuring the data than the information and retrieval tree data corresponding to entity identification information for identifying entity data representing an entity of the data to be retrieved which is specified by the information or the lower information included in the node information; an input controlling unit configured to output a candidate of the data to be retrieved based on the information or the lower information inputted by a user and the node information stored in the retrieval tree data unit; and an entity data acquiring unit configured to transmit to the retrieval server device a retrieval request including the entity identification information corresponding to the information or the lower information included in the candidate of the data to be retrieved, which is output by the input controlling unit and acquire the entity data identified by the entity identification information from the retrieval server device, and the retrieval server device includes: an entity data storing unit configured to store a plurality of entity identification information pieces for identifying entity data representing an entity of the data to be retrieved and the entity data which correspond to each other; and an entity data managing unit configured to retrieve the data to be retrieved from a plurality of entity data pieces stored in the entity data storing unit, based on the entity identification information included in the node information and the number of candidates of the data to be retrieved which is specified by the information or the lower information, which is included in the retrieval request. 
         [0017]    According to the embodiments of the present invention, the size of the database stored in the car navigation can be reduced without damaging user&#39;s operability during retrieval operation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is an overall configuration diagram of a name candidate presented retrieval system (first embodiment); 
           [0019]      FIG. 2  is an explanatory diagram of retrieval tree data (first embodiment); 
           [0020]      FIG. 3  is an explanatory diagram of entity data (first embodiment); 
           [0021]      FIG. 4  is an explanatory diagram of a retrieval menu screen (first embodiment); 
           [0022]      FIG. 5  is a flowchart (first embodiment) illustrating an operation of a retrieval tree validity judging unit; 
           [0023]      FIG. 6  is an explanatory diagram of a name input screen (first embodiment); 
           [0024]      FIG. 7  is a flowchart illustrating an operation of a name input controlling unit (first embodiment); 
           [0025]      FIG. 8  is a flowchart illustrating an operation of anode information acquiring unit (first embodiment); 
           [0026]      FIG. 9  is a flowchart (first embodiment) illustrating an operation of a candidate information setting unit (first embodiment); 
           [0027]      FIG. 10  is an explanatory diagram of a retrieval result acquiring screen (first embodiment); 
           [0028]      FIG. 11  is a flowchart illustrating an operation of an entity data acquiring unit (first embodiment); 
           [0029]      FIG. 12  is a configuration diagram of an entity data request message (first embodiment); 
           [0030]      FIG. 13  is a configuration diagram of an entity data response message (first embodiment); 
           [0031]      FIG. 14  is a flowchart illustrating an operation of an entity data managing unit (first embodiment); 
           [0032]      FIG. 15  is an explanatory diagram of a retrieval tree data update screen (first embodiment); 
           [0033]      FIG. 16  is a flowchart illustrating an operation of a retrieval tree data updating unit (first embodiment); 
           [0034]      FIG. 17  is an overall configuration diagram of a keyboard controlled retrieval system (second embodiment); 
           [0035]      FIG. 18  is an explanatory diagram of retrieval tree data (second embodiment); 
           [0036]      FIG. 19  is an explanatory diagram of a name input screen (second embodiment); and 
           [0037]      FIG. 20  is a flowchart illustrating an operation of a keyboard controlling unit (second embodiment). 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
       [0038]    Hereinafter, a name candidate presented retrieval system of a first embodiment will be described with reference to  FIGS. 1 to 16 . Further, in the first embodiment and a second embodiment, an example of a system that retrieves data by inputting a name by the English alphabet is disclosed, but the present invention is not limited to using the English alphabet and if the name is retrieved by presenting a candidate, other languages such as Japanese, German, and French or figures (for example, a telephone number corresponding to the name) are applicable. 
         [0039]    In the first embodiment, when a user retrieves facility information, a candidate facility name is displayed whenever the name is input by one character, the facility information is inquired to a retrieval server device at the time when the user selects a candidate name to display the result thereof on a screen. 
         [0040]      FIG. 1  illustrates an overall configuration diagram of the name candidate presented retrieval system of the first embodiment. The system includes a retrieval terminal device  100 , a retrieval server device  200 , and a communication network  300 . 
         [0041]    The retrieval terminal device  100  includes a retrieval tree validity judging unit  110  configured to judge validity of retrieval tree data, a name input controlling unit  120  configured to control inputting of a name, a node information acquiring unit  130  configured to acquire node information from the retrieval tree data, a retrieval tree data recording unit  140  configured to record one or more of retrieval tree data pieces  141 , an entity data acquiring unit  150  configured to inquire entity data to the retrieval server device based on information included in the node information, a candidate name setting unit  160  configured to display a candidate name included in the node information on a name input screen, a retrieval tree data updating unit  180  configured to update the retrieval tree data, and a retrieval controlling unit  190  configured to display various screens required for a series of retrieval operations. 
         [0042]    The retrieval server device  200  includes an entity data recording unit  230  configured to record one or more of index data pieces  231  and entity data  232 , an update retrieval tree data recording unit  240  configured to record one or more of the latest retrieval tree data pieces (update retrieval tree data)  241 , an entity data managing unit  250  configured to process a retrieval request of the entity data, and a retrieval tree data managing unit  280  configured to transmit information of the retrieval tree data to the retrieval terminal device. 
         [0043]    The communication network  300  corresponds to a communication network which is usable in a car navigation, such as a mobile phone network and a wireless communication network as a general communication network. 
         [0044]      FIG. 2  discloses an example of the retrieval tree data  141  recorded in the retrieval tree data recording unit  140 . The retrieval tree data  141  of the first embodiment includes a retrieval tree identifier  1411 , a retrieval tree validity term  1412 , node information (uncompressed data)  1413 , node information (compressed data)  1414 , and a name list  1415 . 
         [0045]    The retrieval tree identifier  1411  is an identifier indicating the type of retrieval tree. In the example of the drawing, “100” is stored and represents retrieval data of a restaurant. The retrieval tree validity term  1412  represents a validity term of the retrieval tree data  141 , and the retrieval tree data of the drawing means data which is valid up to Mar. 31, 2020. 
         [0046]    The node information  1413  and  1414  list information of each node constituting the retrieval tree data  141 . Characters and a list of information indicating the position of lower node information when the characters are input are stored in each node information piece. For example, node information ( 1 ) discloses information of first characters of all names and means that names in which first characters are “A”, “B”, and “D” are present. Similarly, node information ( 2 ) discloses information on a second character when the first character is “A”, and means that a name in which the second character is “A” or “C” is present. Node information ( 3 ) discloses information on a third character when the first character is “A” and the second character is “A”, and means that a name in which the third character is “B” is present. 
         [0047]    Further, “¥0” which is a special control symbol is included in each node information piece, in addition to the general characters. “¥0” represents which part of the name list  1415  a candidate name corresponding to current node information starts. For example, “¥0” of the node information ( 2 ) represents that a candidate name when an input character string is “A” starts from a first row “A” of a name list, and “¥0” of the node information ( 3 ) represents that a candidate name when the input character string is “AA” starts from a second row “AAB” of the name list. 
         [0048]    The above description is similarly applied even to other node information ( 4 ), ( 5 ), ( 6 ), and ( 7 ) disclosed in the drawing. Further, in the following description, the first node information (node information ( 1 )) of the retrieval tree data is called root node information. 
         [0049]    The node information  1413  and  1414  of the first embodiment is listed and recorded in a depth order of layers of the nodes (the order of characters constituting the character string). That is, the node information ( 1 ) corresponding to the first character, the node information ( 2 ) and ( 6 ) corresponding to the second character, the node information ( 3 ), ( 4 ), and ( 7 ) corresponding to the third character, and the node information ( 5 ) corresponding to a fourth character are recorded in sequence. Herein, the node information ( 3 ), ( 4 ), ( 7 ), and ( 5 ) (that is, the node information  1414 ) corresponding to the characters after the third character is stored in the retrieval tree data recording unit  140  in a data compressed state. 
         [0050]    The name list  1415  stores retrievable names, and the number of cases and entity IDs required to inquire the names to the retrieval server device, which are listed and stored in alphabetical order of the names. 
         [0051]      FIG. 3  illustrates examples of the index data  231  and the entity data  232  recorded in the entity data recording unit  230 . The index data  231  holds the retrieval tree identifier, the validity term, and the entity ID, and information on an address in entity data in a table format. In the drawing, two index data pieces are disclosed, and one is index data of which the validity term is up to Mar. 31, 2020 and the other is index data of which the validity term is up to Mar. 31, 2025. The index data of which the validity term is up to Mar. 31, 2025 means that a facility having a name “ACE” is newly maintained, and is added with an entity ID  1005 . Entity data  232  holds the names and various pieces of information subordinated to the names in the table format, and in an example of the drawing, a city name and positional information are disclosed. 
         [0052]    Hereinafter, the first embodiment will be described according to a processing flow when the user performs the retrieval operation. 
         [0053]      FIG. 4  is an explanatory diagram of a retrieval menu screen which the retrieval controlling unit  190  displays at a first stage of the retrieval operation. On the retrieval menu screen  191 , names  192  of retrievable classifications (restaurant, a gas station, and the like) are displayed as a list. The user selects a desired classification to be retrieved on the displayed list. 
         [0054]      FIG. 5  is a flowchart illustrating an operation of the retrieval tree validity judging unit  110 , which is executed after the user selects one of the classifications. The retrieval tree validity judging unit  110  refers to the retrieval tree data  141  corresponding to the selected classification and acquires the retrieval tree validity term  1412 , from the retrieval tree data recording unit  140  (step S 1101 ). Subsequently, the retrieval tree validity judging unit  110  acquires a current time set in the retrieval terminal device  100  (step S 1102 ). Further, the current time may be acquired from a clock device such as a general CMOS clock and acquired by using time information acquired from a global positioning system (GPS) in the case of the car navigation. 
         [0055]    Subsequently, the retrieval tree validity judging unit  110  compares the retrieval tree validity term  1412  acquired in steps S 1101  and S 1102  with the current time to judge the validity of the retrieval tree data  141  (step S 1103 ). Further, the retrieval tree validity judging unit  110  instructs the display of the name input screen  121  to the retrieval controlling unit  190  when the current time is within the validity term (step S 1104 ). Meanwhile, the retrieval tree validity judging unit  110  instructs the display of the retrieval tree data update screen  181  to the retrieval controlling unit  190  when the current time is over the validity term (step S 1105 ). In addition, a processing flow of updating the retrieval tree data will be described below. 
         [0056]      FIG. 6  is an explanatory diagram of the name input screen  121  displayed when the retrieval data is within the validity term. The name input screen  121  of the first embodiment is constituted by a name input column  122  in which the names are input, a keyboard  123  for inputting the characters, and a plurality of candidate name buttons  124  for displaying the candidate names. The candidate name button  124  also serve as a retrieval button that starts the inquiry to the retrieval server device when the user presses the button  124  as well as displaying the candidate names. 
         [0057]    An operation of the name input screen  121  is as follows. First, when the user inputs the character “A” by using the keyboard  123 , “A”, “AAB”, “AAC”, “AAD”, “AAE”, and “AAF” which are the candidate names are displayed on six candidate name buttons  124 , respectively as well as “A” is displayed in the name input column  122 . Subsequently, when the user inputs the character “C” by using the keyboard  123 , “ACD” and “ACE” which are candidate names are displayed on two candidate name buttons  124 , respectively. 
         [0058]      FIG. 7  is a flowchart illustrating an operation of the name input controlling unit  120  for performing the operation. The name input controlling unit  120  first instructs acquisition of the root node information to the node information acquiring unit  130  (step S 1201 ). An operation of the node information acquiring unit  130  will be described below. Subsequently, the name input controlling unit  120  instructs setting of the candidate name to the candidate name button  124  of the name input screen  121 , to the candidate name setting unit  160  (step S 1202 ). An operation of the candidate name setting unit  160  will be described below. Subsequently, the name input controlling unit  120  judges whether or not a retrieval target name is determined as a result of processing of the candidate name setting unit  160  (step S 1203 ). Further, the determination of the name means a state in which the user need not input the name any longer, such as a case in which a corresponding name is not present even though the next character is input. 
         [0059]    The name input controlling unit  120  waits for pressing of the button by the user when the name is not determined as the result of judgment of step S 1203  (step S 1204 ). When the button is pressed, the name input controlling unit  120  first judges whether the pressed button is the candidate name button  124  (retrieval button) (step S 1205 ). Meanwhile, when the pressed button is not the candidate name button  124  (retrieval button), that is, when the character is input by using the keyboard  123 , the name input controlling unit  120  instructs acquisition of node information corresponding to the pressed character among lower node information of the node information which is completely acquired, to the node information acquiring unit  130  (step S 1206 ). The name input controlling unit  120  acquires the lower node information and thereafter, repeats the processing from step S 1202 . During the repeated processing, when it is judged that the name is determined in step S 1203  and when the candidate name button (retrieval button)  124  is pressed in step S 1205 , the name input controlling unit  120  acquires the number of cases and an entity ID corresponding to the pressed candidate name button (retrieval button)  124  from the candidate name setting unit  160 , notifies the number of cases and the entity ID to the retrieval controlling unit  190  to instruct the display of the retrieval result acquiring screen  151  (step S 1207 ). 
         [0060]      FIG. 8  is a flowchart illustrating an operation of the node information acquiring unit  130 , which is executed in steps S 1201  and S 1206  of  FIG. 7 . The node information acquiring unit  130  first judges whether or not a node receiving the instruction of acquisition from the name input controlling unit  120  is the root node information (step S 1301 ). The node information acquiring unit  130  judges whether or not the character corresponding to the node receiving the instruction of the acquisition from the name input controlling unit  120  is included in the node information ( 1 ) illustrated in  FIG. 1 , that is, the root node information to judge the root node information. 
         [0061]    When the instruction of the acquisition of the root node information is received, the node information acquiring unit  130  sets a first node of the node information  1413  included in the retrieval tree data  141  as the acquisition target node (step S 1302 ). When acquisition of not the root node information but the lower node information is received, the node information acquiring unit  130  sets as node information corresponding to an input character as the acquisition target node in the lower node information included in the currently acquired node information (step S 1303 ). 
         [0062]    Subsequently, the node information acquiring unit  130  judges which information of the node information (uncompressed data)  1413  and the node information (compressed data)  1414  the acquisition target node is included in (step S 1304 ). The judgment is achieved by verifying how many characters there are before the character that the acquisition target node corresponds to. That is, as described in  FIG. 2 , in the retrieval tree data  141  of the first embodiment, since a node corresponding to a character after the third character of the name is compressed, when the acquisition target node corresponds to the character after the third character, it is judged that the acquisition target node is included in the compressed data. Subsequently, when the acquisition target node information is included in the node information (compressed data)  1414 , the node information acquiring unit  130  decompresses the compressed data (step S 1305 ). Finally, the node information acquiring unit  130  reads the acquisition target node information from the retrieval tree data  141  (S 1306 ). 
         [0063]      FIG. 9  is a flowchart illustrating an operation of the candidate name setting unit  160 , which is executed in step S 1202  of  FIG. 7 . The candidate name setting unit  160  first acquires and stores the candidate name, the number of cases, and the entity ID from the position on the name list  1415  represented by the control symbol “¥0” included in the node information, by referring to the node information acquired by the node information acquiring unit  130  (step S 1601 ). The acquiring is achieved by reading up to a row just before a row where a lead of the name does not coincide with the input character string downward from a start position in the name list represented by the node information by setting the number of (six) candidate name buttons (retrieval buttons)  124  included in the name input screen  121  as the upper limit. For example, when the input character string is “AC”, up to a 9th row just before a 10th row (“AUTO”) where the lead of the name does not coincide with the input character string “AC”, from an 8th row (“ACD”) of the name list displayed by the node information ( 4 ) are acquired as the candidate names. 
         [0064]    Subsequently, the candidate name setting unit  160  sets the acquired candidate names with respect to the candidate name buttons (retrieval buttons)  124 , respectively (step S 1602 ). Subsequently, the candidate name setting unit  160  judges whether or not the lower node information is included in the node information acquired by the node information acquiring unit  130  (step S 1603 ). When the lower node information is not present, the candidate name setting unit  160  notifies to the name input controlling unit  120  that the name is determined (step S 1604 ). 
         [0065]      FIG. 10  is an explanatory diagram of the retrieval result acquiring screen  151 , which is displayed as the result of execution of step S 1207  of  FIG. 7 . In the drawing, data associated with the name “ACE” is inquired to the retrieval server device. The retrieval terminal device  100  displays a pop-up message  152  representing that information is acquired from the retrieval server device  200 , on the retrieval result acquiring screen  151 , at the time of starting the inquiry on the name “ACE”. Further, in the present invention, a form representing while the information is acquired from the retrieval server device  200  is not limited to the pop-up message  152 , but a method generally used to notify to the user that the system is in communication, such as a case where a screen of a mobile phone used for connection with the communication network  300  is changed to a communication state may be used. After the inquiry result is acquired from the retrieval server device  200 , a retrieval result display screen  153  is displayed and a result list  154  is displayed. The user selects data to be targeted from the displayed list to set the data as a destination of the car navigation or verify detailed information. 
         [0066]      FIG. 11  is a flowchart illustrating an operation of the entity data acquiring unit  150  for performing the operation. The entity data acquiring unit  150  first transmits an entity data request message to be illustrated in  FIG. 12  to the entity data managing unit  250  through the communication network  300  (step S 1501 ). Subsequently, the entity data acquiring unit  150  receives an entity data response message to be illustrated in  FIG. 13 , from the entity data managing unit  250  through the communication network  300  (step S 1502 ). After receiving the entity data response message, the entity data acquiring unit  150  displays information included in the acquired entity data on the retrieval result display screen  153  (step S 1503 ). 
         [0067]      FIG. 12  is a configuration diagram of the entity data request message transmitted in step S 1501  of  FIG. 11 . The entity data request message is constituted by a retrieval tree identifier  1511 , an entity ID  1512 , and a number-of-cases  1513 . 
         [0068]      FIG. 13  is a configuration diagram of the entity data response message received in step S 1502  of  FIG. 11 . The entity data response message includes a plurality of names  2511 , a city name  2512 , and positional information  2513 . 
         [0069]      FIG. 14  is a flowchart illustrating an operation of the entity data managing unit  250  when the entity data request message of  FIG. 12  is received. The entity data managing unit  250  first acquires the corresponding index data  231  by referring to the retrieval tree identifier  1511  included in the entity data request message (step S 2501 ). Subsequently, the entity data managing unit  250  acquires from the index data  231  address information corresponding up to an entity ID acquired by subtracting 1 from a value acquired by adding the number-of-cases  1513  to a value represented by the entity ID  1512 , from the value represented by the entity ID  1512 , by referring to the entity ID  1512  and the number-of-cases  1513  included in the entity data request message (step S 2502 ). 
         [0070]    For example, in the case of the entity data request message illustrated in  FIG. 12 , the entity data managing unit  250  acquires the address information corresponding to three entity IDs  1002 ,  1003 , and  1004 . Finally, the entity data managing unit  250  acquires data corresponding to the acquired address information from the entity data  232  (step S 2503 ). The acquired entity data is transmitted to the data acquiring unit  150  as the entity data response message illustrated in  FIG. 13 , which is displayed on the retrieval result display screen  153 . The above is the flow of the retrieval processing by the name candidate presented retrieval system of the first embodiment. 
         [0071]    Subsequently, in step S 1103  of  FIG. 5  described above, update processing of the retrieval tree data which is executed when the retrieval tree data is not within the validity term will be described. 
         [0072]      FIG. 15  is an explanatory diagram of the retrieval tree data update screen  181 , which is displayed when the retrieval data is not within the validity term. The retrieval tree data update screen  181  is constituted by a pop-up message  182  to notify to the user that the validity term of the retrieval tree data is terminated, and buttons  183  and  184  for the user to select whether or not updating is continued. On this screen, when the “Yes” button  183  is pressed, the pop-up message  185  to notify to the user that the retrieval tree data is being updated is displayed, and after the updating of the retrieval tree data is completed, the name input screen  121  illustrated in  FIG. 6  is displayed. When the user presses the “No” button  184 , the process returns to the retrieval menu screen  191  illustrated in  FIG. 4 . 
         [0073]      FIG. 16  is a flowchart illustrating an operation of the retrieval tree data updating unit  180  for performing the operation. The retrieval tree data updating unit  180  first acquires a validity term of new retrieval tree data through the communication network  300  (step S 1801 ). The processing is implemented by the retrieval tree data managing unit  280  by transmitting the retrieval tree identifier  1411  included in the retrieval tree data  141  to the retrieval tree data managing unit  280  and returning a validity term of the latest update retrieval tree data  241  having the same retrieval tree identifier as the received retrieval tree identifier  1411 . Subsequently, the retrieval tree data updating unit  180  displays the received validity term on the screen and inquires to the user whether or not the retrieval tree data is updated (steps S 1802  and S 1803 ). When the user selects updating continuation, the retrieval tree data updating unit  180  transmits the retrieval tree identifier  1411  to the retrieval tree data managing unit  280  through the communication network  300 , and acquires the latest update retrieval tree data  241  to record the acquired latest update retrieval tree data  241  in the retrieval tree data recording unit  140  (step S 1804 ). The retrieval tree data updating unit  180  updates the retrieval tree data and thereafter, instructs the display of the name input screen  121  to the retrieval controlling unit  190  (step S 1805 ). When the user does not select the updating continuation in step S 1803 , the retrieval tree data updating unit  180  instructs the display of the retrieval menu screen  191  to the retrieval controlling unit  190  (step S 1806 ). The above is the flow of the retrieval tree data update processing by the name candidate presented retrieval system of the first embodiment. 
         [0074]    By a content described above, since the retrieval tree data for displaying the candidate name is stored in the retrieval terminal device and communication processing does not thus occur, the user&#39;s operability at the time of inputting the name is not impaired. Further, when the node information is acquired from the retrieval tree data, since the compressed data is decompressed in step S 1305  of  FIG. 8  only when the user inputs characters after the third character, operability does not deteriorate by decompressing the compressed data up to an input of the second character. In addition, in the embodiment, the node information corresponding after the third character is set as a compressed target, but the compression target is not limited to the node information after the third character, but may be set in accordance with a distribution of the lengths of the names included in the retrieval data. 
         [0075]    In detail, node information, which is included in a range where a time required to decompress the compressed data is equal to or less than a predetermined threshold according to a distribution of character numbers included in the node information of each layer in the node information constituting the retrieval tree data  141  illustrated in  FIG. 2 , may be set as the compression target. For example, the distribution of the character numbers included in the respective node information is acquired, like a character number n ( 2 ) included in the node information ( 2 ) similarly thereto, in addition to A and C, a character number n ( 3 ) included in the node information ( 3 ) similarly thereto in addition to B, and a character number n ( 4 ) included in the node information ( 4 ) similarly thereto in addition to D and E, and node information in a range of a comparatively small character number in the distribution is set as node information that satisfies a condition in which the decompressing time of the compressed data is equal to or less than a predetermined threshold value, and the node information may be set as the compression target. By determining data as the compression target according to the distribution of the character numbers included in the node information, the compressed data may be more flexibly set by considering the decompressing time. 
         [0076]    Further, by the content described above, since the entity data referred to from the retrieval tree data may be stored in the retrieval server device, the size of the data stored in the retrieval terminal device may be reduced. 
       Second Embodiment 
       [0077]    Hereinafter, a keyboard controlled retrieval system of a second embodiment will be described with reference to  FIGS. 17 to 20 . In the second embodiment, when the user retrieves the facility information, a display of the corresponding number of cases and a control to enable only a key corresponding to a character which is inputtable next to be pressed is performed whenever the tile is input by one character, and the facility information is inquired to the retrieval server device and the result is displayed on the screen at the time when the user presses the retrieval button. 
         [0078]      FIG. 17  illustrates an overall configuration diagram of the keyboard controlled retrieval system of the second embodiment. A basic configuration is the same as that of the first embodiment, but differences from the first embodiment are in that the candidate name setting unit  160  in  FIG. 1  is not present, a keyboard controlling unit  170  is newly added, and the configuration of the retrieval tree data  141  recorded in the retrieval tree data recording unit  140  of  FIG. 1  is changed to retrieval tree data  142 . The second embodiment is basically the same as the first embodiment in terms of other parts. 
         [0079]      FIG. 18  illustrates an example of the retrieval tree data  142  in the second embodiment. The retrieval tree data  142  of the second embodiment includes a retrieval tree identifier  1421 , a retrieval tree validity term  1422 , node information (uncompressed data)  1423 , and node information (compressed data)  1424 . The second embodiment is the same as the first embodiment in the retrieval tree identifier  1421  and the retrieval tree validity term  1422 . 
         [0080]    The node information  1423  and  1424  list information of each node constituting the retrieval tree data  142 . Characters, the number of cases when the characters are input, and a list of information indicating the position of lower node information when the characters are input are stored in each node information piece. For example, the node information ( 1 ) represents that the number of cases when “A” is input is 21 and the number when “B” is input is 26. It is the same in other characters. 
         [0081]    Further, “¥0” which is a special control symbol is included in each node information piece, in addition to the general characters. When the character is “¥0”, a value acquired by adding up the numbers of all characters included in the node information is stored in a column in which the corresponding number of cases is stored, and an entity ID corresponding to the node information is recorded in a column representing the position of the lower node information. For example, the node information ( 4 ) is node information acquired when the user inputs the characters in the order of “AC”, and means that the number of cases when the input is “AC” is 12 and the entity ID in the case is 998. 
         [0082]    Each node information piece constituting the node information (uncompressed data)  1423  and the node information (compressed data)  1424  of the second embodiment is listed and recorded in the order of the number represented by “¥0”. That is, the node information ( 1 ) of which the largest number of cases is 67 is disposed at the lead and subsequently, the node information ( 6 ) of which the number is 26 is disposed. It is the same even with respect to subsequent nodes. Herein, the node information ( 3 ) and ( 5 ) of which the number of cases is 10 or less is stored in the retrieval tree data recording unit  140  in the data compressed state. 
         [0083]    Hereinafter, the second embodiment will be described according to a processing flow when the user performs the retrieval operation. A flow until the name input screen is displayed is the same as that of the first embodiment. 
         [0084]      FIG. 19  is an explanatory diagram of the name input screen  121  displayed in the keyboard controlled retrieval system of the second embodiment. The name input screen  121  includes the name input column  122  of inputting the names, the keyboard  123  for inputting the characters, and the retrieval button  124 , similarly as the first embodiment. Further, the retrieval button  124  displays the candidate names in the first embodiment, but displays “retrieval” as a name of the button in the second embodiment. Further, the name input screen  121  of the second embodiment includes a number displaying column  125  displaying the number of input names. 
         [0085]    In an initial screen illustrated in  FIG. 19 , “67” is displayed in the number-of-cases displaying column  125 . This represents that the number of retrievable data pieces is 67. Some buttons such as buttons “C”, “F”, and “Q” of the keyboard  123  are set in an unpressable state. This represents that no name in which the first character starts as “C”, “F”, and “Q” is present in the database (retrieval tree data  142 ). In this state, when the user inputs “A” by using the keyboard  123 , the value of the number-of-cases displaying column  125  is changed to “21” and further, the keyboard  123  is set in a state in which some buttons such as buttons “B”, “D”, and “E” are unpressable. This represents that the number of cases in which the first character is “A” is 21 and a name in which the first character is “A” and the second character is “B”, “D”, and “E” is not present in the database. As such, in the keyboard controlled retrieval system of the second embodiment, whenever the user inputs one character, the display of the number of cases and the control to enable only the key which is inputtable next to be pressed are performed. 
         [0086]    Operations of the name input controlling unit  120 , the node information acquiring unit  130 , and the keyboard controlling unit  170  will be described below with respect to processing for performing the operation illustrated in  FIG. 19 . 
         [0087]    The operation of the name input controlling unit  120  is the same as that of the first embodiment, except that the configuration that instructs the setting of the candidate name to the candidate name setting unit  160  in step S 1202  of  FIG. 7  is changed to processing to instruct the display of the number of cases and the control of the keyboard to the keyboard controlling unit  170 . 
         [0088]    The operation of the node information acquiring unit  130  is the same as that of the first embodiment, except that a reference for judging whether or not the acquisition target node is present in the compressed data in step S 1304  of  FIG. 8  is how many characters of the name there are before the character that the target node corresponds to in the first embodiment, while as the reference, whether the number of cases corresponding to the target node is 10 or less is used in the second embodiment. 
         [0089]    In regard to the keyboard controlling unit  170 , a flowchart illustrating the operation of the keyboard controlling unit  170  is illustrated in  FIG. 20 . The keyboard controlling unit  170  first displays the number of cases indicated by “¥0” of the node information acquired by the node information acquiring unit  130  in the number displaying column  125  of the name input screen  121  of the second embodiment (step S 1701 ). Subsequently, the keyboard controlling unit  170  is set to press only the key corresponding to the character included in the node information in the keyboard  123  (step S 1702 ). Subsequently, the keyboard controlling unit  170  stores the number of cases and the entity ID represented by “¥0” of the node information (step S 1703 ). Subsequently, the keyboard controlling unit  170  judges whether or not the lower node information is included in the node information (step S 1704 ). When the lower node information is not present, the keyboard controlling unit  170  notifies to the name input controlling unit  120  that the name is determined (step S 1705 ). 
         [0090]    In the name input controlling unit  120 , when the name is determined in step S 1203  of  FIG. 7  or when the retrieval button  124  is pressed in step S 1205 , as in the first embodiment, the keyboard controlling unit  170  acquires the number of cases and the entity ID which are stored, and notifies the acquired number of cases and entity ID to the retrieval controlling unit  190  to instruct the display of the retrieval result acquiring screen  151 . Thereafter, processing of acquiring a retrieval result from the retrieval server device by using the number of cases and the entity ID is the same as that of the first embodiment. 
         [0091]    By the content described above, since the retrieval tree data for displaying the number of cases whenever the user inputs one character and performing the control to enable only the key which is inputtable next to be pressed is stored in the retrieval terminal device and thus communication processing does not thus occur, the user&#39;s operability is not impaired. Further, the compressed data is decompressed at the time of acquiring the node information from the retrieval tree data only when the number of cases is 10 or less, and as a result, when the retrieval button  124  is pressed in a state in which the number is more than 10, operability by decompressing the compressed data does not deteriorate. In addition, the node information in which the number of cases is equal to or less than 10 is set as the compression target in the embodiment, but the number of cases is not limited to 10 or less and may be set according to the number of case included in the retrieval data. 
         [0092]    In detail, node information of the number of cases in which a time required to decompress the compressed data is equal to or less than a predetermined threshold according to the number of characters included in the node information of each layer in the node information constituting the retrieval tree data  142  illustrated in  FIG. 18  may be set as the compression target. For example, the number included in each node information is acquired, like  67  which is the number represented by “¥0” in the node information ( 1 ),  21  which is number represented by “¥0” in the node information ( 2 ),  9  which is the number represented by “¥0” in the node information ( 3 ),  12  which is number represented by “¥0” in the node information ( 4 ),  3  which is the number represented by “¥0” in the node information ( 5 ),  26  which is the number represented by “¥0” in the node information ( 6 ), and  18  which is the number represented by “¥0” in the node information ( 7 ), and the node information is listed in the order in which the number is larger, and node information of the comparatively small number (for example, three lower node information in which the number is small) is set as node information to satisfy the condition in which the decompressing time of the compressed data is equal to or less than the predetermined threshold value, and the node information may be set as the compression target. As such, by determining data as the compression target according to the number of characters included in the node information, the compressed data may be more flexibly set by considering the decompressing time. 
         [0093]    Further, as in the first embodiment, since the entity data referred to from the retrieval tree data may be stored in the retrieval server device, the size of the data stored in the retrieval terminal device may be reduced. 
         [0094]    In addition, in the first embodiment and the second embodiment described above, node information in which the layer is deeper than any layer (for example, node information corresponding to a character displayed when the retrieval result is sufficiently narrowed) in the node information included in the retrieval tree data is referred to as node information which is small in the number, that is, node information of which a referred frequency is low, and as a result, only the node information may be set as the compression target. In this case, since node information of which a reference frequency is high is not compressed, an occurrence frequency of a stand-by time which is generated according to the decompressing of the compressed data may be reduced and user convenience may be further improved. 
         [0095]    As such, as illustrated in the first embodiment and the second embodiment, for example, data (retrieval tree data) required whenever the user inputs one character as the name of the retrieval target is stored in the car navigation in the database required to retrieve the facility data, and an entity (data of a facility name, an address, a telephone number, and the like, that is, entity data) of the retrieval data referred to from the retrieval tree data is stored in an external retrieval server device connected through the communication network, processing to improve the user&#39;s operability at the time of inputting the name is executed by referring to the retrieval tree data stored in the car navigation, and the entity data is inquired to the retrieval server device at the time when the user instructs retrieval execution or at the time when the retrieval tree data is referred to, and as a result, it may be judged that more characters does not need to be inputted, and the result is displayed on the screen of the car navigation. As such, the data which significantly influences the user&#39;s operability is stored in the car navigation to reduce the size of the database stored in the car navigation without impairing the user&#39;s operability. 
         [0096]    Further, the retrieval tree data stored in the car navigation is partially compressed. For example, when the user inputs the name of the retrieval target, a long name is rarely input to the end and in general, there are many cases in which the retrieval processing is executed at the time when a predetermined length is input to select a name to be targeted from a result list. That is, there are many cases in which a node corresponding to a character close to the lead of the name is particularly referred, but a node corresponding to a character close to the end of the name is not referred, among a plurality of nodes constituting the retrieval tree data. Only the node of which the reference frequency is low is selectively compressed to reduce the size of the database stored in the car navigation without impairing the user&#39;s operability. 
         [0097]    In addition, when the retrieval tree data updating unit updates the retrieval tree data, the data recording unit stores history information such as the number of times or a time to access the node information included in retrieval tree data in the past, and the node information of which the number of access times is small of the stored history information may be set as the compression target. As such, by determining the data to be compressed according to the history of the access to the node information, the compressed data may be set more efficiently. 
         [0098]    The present invention is not limited to only the embodiments, but in the execution step, the components may be transformed and actualized within the scope without departing from the spirit thereof. For example, the retrieval method or the compression method disclosed in the first embodiment and the second embodiment may be, of course, appropriately combined or implemented in all selectable formats.