Abstract:
A non-transitory computer-readable recording medium stores an encoding program that causes a computer to execute a process. The process includes first encoding a first character string in input data to a first code, when the first character string being registered in a first dictionary, the first code being associated with the first character string in the first dictionary; second encoding a second character string in input data to a second code and registering the second character string to a dynamic dictionary, when the second character string being not registered in the first dictionary, the second code being associated with the second character string and preliminary information in the dynamic dictionary; and generating encoded data including the encoded input data and the dynamic dictionary.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2015-140880, filed on Jul. 14, 2015, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    The embodiments discussed herein are related to a encoding program, a encoding method, an information processing device, a replacement program, and a replacement method. 
       BACKGROUND 
       [0003]    Known is a technique for compressing (encoding) text data using a dictionary. For example, a word matching with a dictionary included in a computer that performs compression processing is replaced with a previously associated code in the dictionary. Conventional technologies are described in Japanese Laid-open Patent Publication No. 5-181641 and Japanese Laid-open Patent Publication No. 2000-201080, for example. 
         [0004]    The number of words held in a dictionary included in a computer that performs compression processing is limited, so that a word not registered in the dictionary may appear in text data as a compression target. The number of held words may be different depending on a scale of the computer. For example, a dictionary having a small amount of data is used in a terminal device such as a cellular telephone and a smartphone to suppress a storage capacity to be used. On the other hand, a large-scale dictionary holding various pieces of information is used in a server computer such as a cloud system to perform data mining, for example. In this way, the number of words held in the dictionary may be different between the terminal device and the cloud system. 
         [0005]    Expansion processing for compressed data on which compression processing is performed is not necessarily performed by the same computer as the computer that has performed the compression processing. Thus, the dictionary used for compression processing is limited to a dictionary that can be utilized in any computer that can perform expansion processing. For example, when compressing data to be also expandable by the terminal device, the cloud system compresses the data using a dictionary that can be utilized in the terminal device even when a large-scale dictionary can be utilized. Due to this, the compressed data can be expanded by the terminal device. However, such compressed data is not effectively utilized in other computers including the large-scale dictionary. 
       SUMMARY 
       [0006]    According to an aspect of an embodiment, a non-transitory computer-readable recording medium stores an encoding program that causes a computer to execute a process. The process includes first encoding a first character string in input data to a first code, when the first character string being registered in a first dictionary, the first code being associated with the first character string in the first dictionary; second encoding a second character string in input data to a second code and registering the second character string to a dynamic dictionary, when the second character string being not registered in the first dictionary, the second code being associated with the second character string and preliminary information in the dynamic dictionary; and generating encoded data including the encoded input data and the dynamic dictionary. 
         [0007]    The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
         [0008]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0009]      FIG. 1  is a diagram schematically illustrating a procedure of compression processing; 
           [0010]      FIG. 2  is a diagram schematically illustrating a procedure of replacement retrieval; 
           [0011]      FIG. 3  is a diagram illustrating an example of a configuration of a terminal device; 
           [0012]      FIG. 4A  is a diagram illustrating an example of a data configuration of a bit filter part of a static dictionary; 
           [0013]      FIG. 4B  is a diagram illustrating an example of a data configuration of a dictionary part of the static dictionary; 
           [0014]      FIG. 4C  is a diagram conceptually illustrating a data configuration of the static dictionary; 
           [0015]      FIG. 5  is a diagram illustrating an example of a data configuration of a decoding dictionary; 
           [0016]      FIG. 6A  is a diagram illustrating an example of a data configuration of a dynamic bit filter part of a dynamic dictionary; 
           [0017]      FIG. 6B  is a diagram illustrating an example of a data configuration of a pointer part of the dynamic dictionary; 
           [0018]      FIG. 6C  is a diagram illustrating an example of a data configuration of a buffer part of the dynamic dictionary; 
           [0019]      FIG. 7A  is a diagram illustrating an example of a state in which a compressed code dynamically assigned to a low frequency word is registered in the dynamic dictionary; 
           [0020]      FIG. 7B  is a diagram illustrating an example of a state in which a compressed code dynamically assigned to an unknown word is registered in the dynamic dictionary; 
           [0021]      FIG. 8A  is a diagram schematically illustrating a procedure for compressing a high frequency word; 
           [0022]      FIG. 8B  is a diagram schematically illustrating a procedure for compressing the low frequency word; 
           [0023]      FIG. 8C  is a diagram schematically illustrating a procedure for compressing the unknown word; 
           [0024]      FIG. 9  is a diagram illustrating an example of a configuration of a server device; 
           [0025]      FIG. 10A  is a diagram schematically illustrating a procedure for decoding the high frequency word; 
           [0026]      FIG. 10B  is a diagram schematically illustrating a procedure for decoding the low frequency word; 
           [0027]      FIG. 10C  is a diagram schematically illustrating a procedure for decoding the unknown word; 
           [0028]      FIG. 11  is a flowchart illustrating an example of a process of compression processing; 
           [0029]      FIG. 12  is a flowchart illustrating an example of a process of replacement processing; 
           [0030]      FIG. 13  is a flowchart illustrating an example of a process of decoding processing; 
           [0031]      FIG. 14  is a diagram schematically illustrating the procedure of compression processing; 
           [0032]      FIG. 15  is a diagram illustrating an example of a computer that executes a compression program; and 
           [0033]      FIG. 16  is a diagram illustrating a computer that executes a replacement program. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0034]    Preferred embodiments of the present invention will be explained with reference to accompanying drawings. The scope of the invention is not limited by the embodiments. The embodiments can be appropriately combined without causing contradiction in processing content. 
       [a] First Embodiment 
     Compression (Encoding) Processing 
       [0035]    First, the following schematically describes compression processing with reference to  FIG. 1 .  FIG. 1  is a diagram schematically illustrating a procedure of compression processing. The following exemplifies a case in which a terminal device  10  such as a cellular telephone or a smartphone compresses (encodes) “ . . . a pen . . . Mickey . . . ” included in a compression target file  32  as a target of compression processing. 
         [0036]    To compress the compression target file  32 , a compression unit  40  of the terminal device  10  reads out each word from a document included in the compression target file  32  in units of a word ( FIG. 1  ( 1 )). In the example of  FIG. 1 , the compression unit  40  reads out “a”, “pen”, and “Mickey”. The compression unit  40  then collates the acquired word with a static dictionary  34  ( FIG. 1  ( 2 )) 
         [0037]    The static dictionary  34  is a dictionary for compression storing a compressed code for each word. A specific configuration of the static dictionary  34  will be described later. In the static dictionary  34 , the compressed code is registered for a high frequency word the appearance frequency of which is high. For example, general words such as an article, a verb, and a noun having high appearance frequency in a general sentence are registered as high frequency words in the static dictionary  34 . Technical terms and proper nouns such as a place name and a name are regarded as unknown words having low appearance frequency, and not registered in the static dictionary  34 . In the example of  FIG. 1 , “a” and “pen” are regarded as the high frequency words, and “Mickey” is regarded as the unknown word. In the static dictionary  34 , a unique basic code for identifying a word is defined for the registered word, and a compressed code is registered for the high frequency word. In the static dictionary  34 , basic codes and compressed codes for “a” and “pen” are registered, and a basic code and a compressed code for “Mickey” are not registered. For example, in the static dictionary  34 , the basic code “A00001h” and the compressed code “4000h” are registered corresponding to “a”, and the basic code “A02000h” and the compressed code “4AAAh” are registered corresponding to “pen”. The sign “h” attached to each end of the basic code and the compressed code indicates that the code is represented by hexadecimal numbers. 
         [0038]    As a result of collation, if the compressed code corresponding to the collated word is registered in the static dictionary  34 , the compression unit  40  acquires the compressed code for the collated word from the static dictionary  34 . The compression unit  40  then converts the collated word into the compressed code and outputs the compressed code to a compressed file  33  ( FIG. 1  ( 3 )). In the example of  FIG. 1 , “a” is registered in the static dictionary  34 . The compression unit  40  converts “a” into the compressed code “4000h” and outputs the compressed code to the compressed file  33 . 
         [0039]    As a result of collation, if the compressed code corresponding to the collated word is not registered in the static dictionary  34 , the compression unit  40  assigns a new compressed code to the collated word. The compression unit  40  registers the collated word, the assigned new compressed code, and a preliminary code in a dynamic dictionary  31  ( FIG. 1  ( 4 )). The dynamic dictionary  31  includes a pointer part  31 B and a buffer part  31 C. A specific configuration of the dynamic dictionary  31  will be described later. The pointer part  31 B includes a region of “compressed code” in which the compressed code is stored, a region of “pointer” in which the pointer is stored, and a region of “preliminary code” in which the preliminary code is stored. The registered word is stored in the buffer part  31 C. The assigned new compressed code is stored in the region of “compressed code” of the pointer part  31 B. The preliminary code is stored in the region of “preliminary code”. A pointer indicating a storing position of the word in the buffer part  31 C is stored in the region of “pointer”. In the example of  FIG. 1 , the compression unit  40  assigns the compressed code “A001h” to “Mickey”. The compression unit  40  stores “Mickey” in the buffer part  31 C. The compression unit  40  stores “A001h” in the region of “compressed code” of the pointer part  31 B, stores the pointer indicating the storing position of “Mickey” in the buffer part  31 C in the region of “pointer”, and stores “000000h” indicating that the preliminary code is not set yet in the region of “preliminary code”. The compression unit  40  then converts the collated word into the assigned compressed code and outputs the compressed code to the compressed file  33  ( FIG. 1  ( 5 )). In the example of  FIG. 1 , “Mickey” is converted into the compressed code “A001h” and outputs the compressed code to the compressed file  33 . 
         [0040]    After completing compression of the document included in the compression target file  32  in units of a word, the compression unit  40  stores the dynamic dictionary  31  in a trailer of the compressed file  33  ( FIG. 1  ( 6 )). 
         [0041]    Replacement Processing 
         [0042]    Next, the following schematically describes replacement processing with reference to  FIG. 2 .  FIG. 2  is a diagram schematically illustrating a procedure of replacement retrieval. The following exemplifies a case in which a server device  11  in a cloud system and the like performs replacement of the preliminary code on the received compressed file  33 . 
         [0043]    The server device  11  stores a large-scale dictionary  70  in which the compressed code for each word is stored. In the large-scale dictionary  70 , various pieces of information are registered for a larger number of words than that in the static dictionary  34  illustrated in  FIG. 1 . For example, in the large-scale dictionary  70 , the basic codes are defined for a larger number of words than that in the static dictionary  34  illustrated in  FIG. 1 , and compressed codes are registered for high frequency words. In the large-scale dictionary  70 , a part of speech of each word is registered. The large-scale dictionary  70  may be one dictionary, or may include a plurality of dictionaries. For example, the large-scale dictionary  70  includes a plurality of dictionaries including the static dictionary  34 . In the large-scale dictionary  70 , the basic code “A00001h”, the compressed code “4000h”, and the part of speech “article” are registered corresponding to “a”. In the large-scale dictionary  70 , “A02000h”, the compressed code “4AAAh”, and the part of speech “common noun” are registered corresponding to “pen”. In the large-scale dictionary  70 , the basic code “AFFFFFh” and the part of speech “proper noun” are registered corresponding to “Mickey”. 
         [0044]    In the example of  FIG. 2 , a replacement unit  52  of the server device  11  reads out the dynamic dictionary  31  from the trailer of the compressed file  33  ( FIG. 2  ( 1 )). The replacement unit  52  refers to the word registered in the dynamic dictionary  31 , and determines whether the word registered in the dynamic dictionary  31  is registered in the large-scale dictionary  70  ( FIG. 2  ( 2 )). If a word registered in the dynamic dictionary  31  is registered in the large-scale dictionary  70 , the replacement unit  52  replaces the preliminary code corresponding to the word in the dynamic dictionary  31  with the basic code corresponding to the word in the large-scale dictionary  70  ( FIG. 2  ( 3 )). In the example of  FIG. 2 , “AFFFFFh” is registered corresponding to “Mickey” in the large-scale dictionary  70 . The replacement unit  52  replaces a preliminary code region corresponding to the compressed code “A001h” of “Mickey” with “AFFFFFh”. 
         [0045]    Accordingly, in the server device  11 , the unknown word included in the compressed file  33  can be associated with the large-scale dictionary  70  while keeping a state in which the compressed file  33  is compressed, and the server device  11  can specify what is the unknown word or specify the part of speech of the word. The server device  11  can perform various types of processing such as data mining on the compressed data compressed into the compressed file  33  including the unknown word, and can cause the compressed data compressed into the compressed file  33  to be utilized more effectively. An unregistered character string is registered in the compressed file  33 , so that the compressed file  33  can be decoded by a second terminal device including only a standard dictionary  30 . By replacing the preliminary code corresponding to the word in the dynamic dictionary  31  with the basic code corresponding to the word in the large-scale dictionary  70 , a second cloud system including the large-scale dictionary  70  can associate the unknown word included in the compressed file  33  with the large-scale dictionary  70 , and can perform various types of processing such as data mining including the unknown word. 
         [0046]    Device Configuration 
         [0047]    The following describes a configuration of each device. First, the configuration of the terminal device  10  will be described.  FIG. 3  is a diagram illustrating an example of the configuration of the terminal device. The terminal device  10  is a device that performs coding such as compression of the compression target file  32 . The terminal device  10  is an information processing device such as a cellular telephone, a smartphone, a tablet terminal, and a personal computer. As illustrated in  FIG. 3 , the terminal device  10  includes a memory unit  20  and a control unit  21 . The terminal device  10  may include units other than the above-described units included in the information processing device. 
         [0048]    The memory unit  20  is a storage device such as a hard disk, a solid state drive (SSD), and an optical disc. The memory unit  20  may be a data-rewritable semiconductor memory such as a random access memory (RAM), a flash memory, and a non volatile static random access memory (NVSRAM). 
         [0049]    The memory unit  20  stores an operating system (OS) and various programs to be executed by the control unit  21 . For example, the memory unit  20  stores a computer program for performing compression processing described later. The memory unit  20  further stores various pieces of data used in the program executed by the control unit  21 . For example, the memory unit  20  stores the standard dictionary  30 , the dynamic dictionary  31 , the compression target file  32 , and the compressed file  33 . 
         [0050]    The standard dictionary  30  is dictionary data used for compressing and decoding data. The standard dictionary  30  includes the static dictionary  34  and a decoding dictionary  35 . 
         [0051]    The static dictionary  34  is data holding conversion information for associating a word with a compressed code. The static dictionary  34  is used for compressing data. The static dictionary  34  includes a bit filter part  34 A and a dictionary part  34 B. 
         [0052]    The following describes a data configuration of the static dictionary  34  with reference to  FIGS. 4A to 4C .  FIG. 4A  is a diagram illustrating an example of the data configuration of the bit filter part of the static dictionary. The bit filter part  34 A includes items of “2-gram”, “bit map”, and “pointer”. 
         [0053]    The item of “2-gram” is a region for storing a 2-gram character included in each word. For example, as illustrated in  FIG. 4A , “able” includes 2-gram characters corresponding to “ab”, “bl”, and “le”. The item of “bit map” is a region for storing a bit string that represents a position at which the 2-gram character is included in the word. For example, when the bit map of 2-gram “ab” is “1_0_0_0_0”, the bit map represents that the first two characters of the word are “ab”. The item of “pointer” is a region for storing the pointer indicating the storing position in the dictionary part  34 B at which the word corresponding to the bit map is stored. The bit map is associated with each word by the pointer. 
         [0054]      FIG. 4B  is a diagram illustrating an example of the data configuration of the dictionary part of the static dictionary. The dictionary part  34 B includes items of “basic word”, “length of character string”, “number of times of appearance”, “code length”, “static code”, “dynamic code”, and “basic code”. 
         [0055]    The item of “basic word” is a region for storing a word registered in advance as a basic word. For example, in the dictionary part  34 B of the static dictionary  34  illustrated in  FIG. 4B , each word extracted from a certain population is registered as the basic word. For example, about 190,000 words registered in a dictionary and the like are registered as basic words. The item of “length of character string” is a region for storing the number of bytes representing a length of a character string of the word registered in advance as the basic word. The item of “number of times of appearance” is a region for storing the number of times of appearance of the word in the certain population. The item of “code length” is a region for storing the number of bits representing a length of the compressed code assigned to the word. The item of “static code” is a region for storing the compressed code assigned to the word in advance. 
         [0056]    In the present embodiment, the basic words to be registered in the dictionary part  34 B of the static dictionary  34  are divided into high frequency words having relatively high appearance frequency and low frequency words having relatively low appearance frequency. In the present embodiment, the 1st to 8192nd basic words are assumed to be the high frequency words, and the 8193rd and subsequent basic words are assumed to be the low frequency words in descending order of appearance frequency. To the high frequency word, a short compressed code is assigned in advance, and the assigned compressed code is stored in the item of “static code” in advance. To the low frequency word, the compressed code is dynamically assigned when the low frequency word appears, and the assigned compressed code is stored in the item of “dynamic code” in advance. For example, to the high frequency word, a 2-byte (16-bit) compressed code is assigned in advance, and the assigned compressed code is stored in the item of “static code” in advance. To the low frequency word, a 3-byte (24-bit) compressed code is dynamically assigned when the low frequency word appears, and the assigned compressed code is stored in the item of “dynamic code” in advance. That is, the compressed code is registered in advance for the high frequency word, and is not registered for the low frequency word in an initial state. 
         [0057]      FIG. 4C  is a diagram conceptually illustrating the data configuration of the static dictionary. In the static dictionary  34 , the bit filter part  34 A and the dictionary part  34 B are associated with each other via the pointer. The static dictionary  34  can be illustrated to have the data configuration in  FIG. 4C . 
         [0058]    Returning to  FIG. 3 , the decoding dictionary  35  is data holding conversion information for associating a word with a compressed code. The decoding dictionary  35  is used for decoding the compressed data. 
         [0059]      FIG. 5  is a diagram illustrating an example of the data configuration of the decoding dictionary. The decoding dictionary  35  includes items of “static code”, “length of character string”, and “character string”. 
         [0060]    The item of “static code” is a region for storing the compressed code assigned to the word in advance. The item of “length of character string” is a region for storing the length of the character string of the word corresponding to the compressed code. The item of “character string” is a region for storing the character string of the word corresponding to the compressed code. In the decoding dictionary  35 , regarding the high frequency word, the assigned compressed code is stored in the item of “static code”, the length of the character string of the word is stored in the item of “length of character string”, and the character string of the word is stored in the item of “character string”. In the decoding dictionary  35 , regarding the low frequency word, the basic code is stored in the item of “static code”, the length of the character string of the word is stored in the item of “length of character string”, and the character string of the word is stored in the item of “character string”. 
         [0061]    Returning to  FIG. 3 , the dynamic dictionary  31  is data holding various pieces of information related to the dynamically assigned compressed code. In the present embodiment, the compressed code is dynamically assigned to each of the low frequency word having low appearance frequency and the unknown word such as a word and a character string not included in the basic words among the basic words registered in the static dictionary  34 . The dynamic dictionary  31  stores the compressed codes dynamically assigned to the words such as the low frequency word and the unknown word. The dynamic dictionary  31  includes a dynamic bit filter part  31 A, a pointer part  31 B, and a buffer part  31 C. 
         [0062]    The following describes a data configuration of the dynamic dictionary  31  with reference to  FIGS. 6A to 6C .  FIG. 6A  is a diagram illustrating an example of the data configuration of the dynamic bit filter part of the dynamic dictionary. The dynamic bit filter part  31 A includes items of “2-gram”, “bit map”, and “pointer”. 
         [0063]    The item of “2-gram” is a region for storing a 2-gram character included in the word. The item of “bit map” is a region for storing a bit string that represents a position at which the 2-gram character is included in the word. The item of “pointer” is a region for storing the pointer indicating the storing position in the pointer part  31 B at which the compressed code assigned to the word corresponding to the bit map is stored. The word is associated with each compressed code by the pointer. 
         [0064]      FIG. 6B  is a diagram illustrating an example of the data configuration of the pointer part of the dynamic dictionary. The pointer part  31 B includes items of “dynamic code”, “classification”, “pointer”, “length”, and “preliminary code”. 
         [0065]    The item of “dynamic code” is a region for storing the dynamically assigned compressed code. The item of “classification” is a region for storing a classification of the word to which the compressed code is assigned. In the present embodiment, the classification “1” is assumed to be the low frequency word, and the classification “2” is assumed to be the unknown word. In the item of “classification”, “1” is stored when the word to which the compressed code is assigned is the low frequency word, and “2” is stored when the word to which the compressed code is assigned is the unknown word. The item of “pointer” is a region for storing the pointer indicating the storing position in the buffer part  31 C at which the word to which the compressed code is assigned is stored. The compressed code is associated with each word to which the compressed code is assigned by the pointer. The item of “length” is a region for storing the length of the word to which the compressed code is assigned. The item of “preliminary code” is a region for storing the preliminary code to be associated with the word to which the compressed code is assigned. In the present embodiment, the item of “preliminary code” is provided to the dynamic dictionary  31  to enable the preliminary code to be associated with the compressed code. 
         [0066]      FIG. 6C  is a diagram illustrating an example of a data configuration of the buffer part of the dynamic dictionary. The buffer part  31 C stores information related to the word to which the compressed code is dynamically assigned. For example, when the word to which the compressed code is dynamically assigned is the low frequency word, the basic code of the word is stored in the buffer part  31 C. When the word to which the compressed code is dynamically assigned is the unknown word, the character string of the unknown word is stored in the buffer part  31 C. 
         [0067]    The following describes an example of a state in which a compressed code dynamically assigned to a word is registered in the dynamic dictionary  31 .  FIG. 7A  is a diagram illustrating an example of the state in which a compressed code dynamically assigned to a low frequency word is registered in the dynamic dictionary. The example of  FIG. 7A  indicates a state in which the compressed code “A000h” that is dynamically assigned to the word “Abject” is registered, the basic code of the word “Abject” being “A0002Ch” illustrated in  FIG. 4C . The basic code “A0002Ch” is registered in the buffer part  31 C. In the pointer part  31 B, the assigned compressed code “A000h” is registered in the item of “dynamic code”, the classification “1” is registered in the item of “classification”, and the pointer indicating the position of the basic code “A0002Ch” is registered in the item of “pointer”. In the pointer part  31 B, the length “3”-byte of the basic code “A0002Ch” is registered in the item of “length”, and an initial value “000000h” indicating that the preliminary code is not registered is registered in the item of “preliminary code”. 
         [0068]      FIG. 7B  is a diagram illustrating an example of a state in which the compressed code dynamically assigned to the unknown word is registered in the dynamic dictionary.  FIG. 7B  exemplifies a state in which the compressed code “A001h” dynamically assigned to the character string “Mickey” as the unknown word is registered. The character string “Mickey” is registered in the buffer part  31 C. In the pointer part  31 B, the assigned compressed code “A001h” is registered in the item of “dynamic code”, the classification “2” is registered in the item of “classification”, and the pointer indicating the position of the character string “Mickey” is registered in the item of “pointer”. In the pointer part  31 B, the length “6”-byte of the character string “Mickey” is registered in the item of “length”, and the initial value “000000h” indicating that the preliminary code is not registered is registered in the item of “preliminary code”. In the dynamic bit filter part  31 A, the pointer toward the compressed code “A001h” is registered in the item of “pointer” of a record of the 2-gram character included in the character string “Mickey”. 
         [0069]    Returning to  FIG. 3 , the compression target file  32  is a file in which text data as a compression target is stored. The compressed file  33  is data obtained by performing compression processing on the compression target file  32 . 
         [0070]    The control unit  21  is a device that controls the terminal device  10 . As the control unit  21 , an electronic circuit such as a central processing unit (CPU) and a micro processing unit (MPU), and an integrated circuit such as an application specific integrated circuit (ASIC) and a field programmable gate array (FPGA) can be employed. The control unit  21  includes programs specifying various processing procedures and an internal memory for storing control data, and performs various types of processing using the programs and the internal memory. The control unit  21  functions as various processing units when various programs operate. For example, the control unit  21  includes the compression unit  40 . 
         [0071]    The compression unit  40  extracts a word from the compression target file  32 , and generates the compressed file  33  in which the compressed code is associated with each word. The compression unit  40  includes an extraction unit  50 , a determination unit  51 , a replacement unit  52 , and a generation unit  53 . 
         [0072]    The extraction unit  50  extracts the character string from the compression target file  32  in units of a word. For example, the extraction unit  50  sequentially reads out the character strings from the compression target file  32 , and extracts words from the read character strings. For example, in a case in which words in a sentence are separated from each other with a certain delimiter such as a space like English, the extraction unit  50  reads out the character string from the compression target file  32 , and separates the character string in units of a word with the delimiter in the character string to extract each word from the character string. For example, in a case in which words in a sentence are not separated from each other with a specific delimiter like Japanese, the extraction unit  50  reads out the character string from the compression target file  32 . The extraction unit  50  performs natural language processing in accordance with a language of the sentence such as morphological analysis and syntactic analysis on the read character string to extract each word from the character string. 
         [0073]    The determination unit  51  performs various determination processes on the word extracted by the extraction unit  50 . For example, the determination unit  51  determines whether the extracted word is the high frequency word, the low frequency word, or the unknown word. For example, the determination unit  51  collates the extracted word with the static dictionary  34 . As a result of collation, if the extracted word does not correspond to any word in the static dictionary  34 , the determination unit  51  determines that the extracted word is an unknown word. That is, if the extracted word is not registered in the static dictionary  34 , the determination unit  51  determines that the extracted word is an unknown word. As a result of collation, if the extracted word corresponds to any word in the static dictionary  34 , the determination unit  51  acquires data of the items of “static code” and “dynamic code” of a corresponding record from the dictionary part  34 B. If the compressed code is stored in the item of “static code”, the determination unit  51  determines that the extracted word is the high frequency word. If the compressed code is not stored in the item of “static code”, the determination unit  51  determines that the extracted word is the low frequency word. If the extracted word is the low frequency word, the determination unit  51  checks data of the item of “dynamic code”. If the compressed code is stored in the item of “dynamic code”, the determination unit  51  determines that the extracted word is the low frequency word that has already been registered in the dynamic dictionary  31 . If the compressed code is not stored in the item of “dynamic code”, the determination unit  51  determines that the extracted word is the low frequency word that is not registered in the dynamic dictionary  31 . 
         [0074]    The replacement unit  52  replaces the word extracted by the extraction unit  50  with the compressed code. For example, if the compressed code corresponding to the extracted word is registered in the static dictionary  34 , the replacement unit  52  specifies the compressed code corresponding to the extracted word. For example, if the extracted word is the high frequency word, the replacement unit  52  specifies the compressed code stored in the item of “static code” as the compressed code corresponding to the word. If the extracted word is the low frequency word that has already been registered in the dynamic dictionary  31 , the replacement unit  52  specifies the compressed code stored in the item of “dynamic code” as the compressed code corresponding to the extracted word. The replacement unit  52  then outputs the specified compressed code corresponding to the word to the generation unit  53 . 
         [0075]    If the extracted word is the unknown word, the replacement unit  52  collates the extracted word with the dynamic dictionary  31 . The replacement unit  52  collates the dynamic bit filter part  31 A of the dynamic dictionary  31  with the extracted unknown word to obtain a corresponding pointer, and determines whether the unknown word is registered. As a result of collation, if the extracted unknown word is registered in the dynamic dictionary  31 , the determination unit  51  replaces the unknown word with the registered compressed code. For example, the replacement unit  52  specifies the compressed code stored in the item of “dynamic code” of the pointer part  31 B as the compressed code corresponding to the unknown word. The replacement unit  52  outputs the specified compressed code corresponding to the unknown word to the generation unit  53 . 
         [0076]    If the extracted word is the unknown word not registered in the dynamic dictionary  31 , or if the extracted word is the low frequency word not registered in the dynamic dictionary  31 , the replacement unit  52  assigns a new compressed code to the extracted word. For example, the replacement unit  52  assigns the new compressed code to the extracted word in accordance with a predetermined assignment rule such as increasing the compressed code one bit by one bit in a predetermined range. In the present embodiment, the replacement unit  52  dynamically assigns a new 3-byte compressed code to the extracted word. The replacement unit  52  then replaces the extracted word with the assigned compressed code. For example, the replacement unit  52  outputs, to the generation unit  53 , the compressed code that is assigned corresponding to the extracted word. The replacement unit  52  associates the extracted word, the dynamically assigned compressed code, and a region for the preliminary code with each other and stores them in the dynamic dictionary  31 . For example, if the extracted word is the low frequency word not registered in the dynamic dictionary  31 , the replacement unit  52  registers the basic code of the extracted word in the buffer part  31 C as illustrated in  FIG. 7A . The replacement unit  52  registers the assigned compressed code in the item of “dynamic code” of the pointer part  31 B, registers “1” in the item of “classification”, and registers the pointer indicating a position of the basic code stored in the buffer part  31 C in the item of “pointer”. The replacement unit  52  registers the length of the basic code in the item of “length” of the pointer part  31 B, and registers the initial value “000000h” in the item of “preliminary code”. The replacement unit  52  also registers the compressed code assigned to the item of “dynamic code” of the record of the extracted word in the static dictionary  34 . If the extracted word is the unknown word not registered in the dynamic dictionary  31 , the replacement unit  52  registers the character string of the extracted word in the buffer part  31 C as illustrated in  FIG. 7B . The replacement unit  52  registers the assigned compressed code in the item of “dynamic code” of the pointer part  31 B, registers “2” in the item of “classification”, and registers, in the item of “pointer”, the pointer indicating the position of the character string of the word stored in the buffer part  31 C. The replacement unit  52  registers, in the item of “length” of the pointer part  31 B, the length of the character string of the word stored in the buffer part  31 C, and registers the initial value “000000h” in the item of “preliminary code”. The replacement unit  52  registers the pointer toward the assigned compressed code in the item of “pointer” of the record of the 2-gram character in the dynamic bit filter part  31 A corresponding to the character string of the word stored in the buffer part  31 C. 
         [0077]    By using the compressed code replaced by the replacement unit  52 , the generation unit  53  generates the compressed file  33  obtained by compressing the compression target file  32 . For example, the generation unit  53  sequentially stores, in the compressed file  33 , the compressed codes that are read out from the compression target file  32  in units of a word and output from the replacement unit  52 , and stores the dynamic dictionary  31  in the compressed file  33  after storing the compressed codes for all of the words and generates the compressed file  33 . 
         [0078]    The following describes a procedure for compressing the high frequency word, the low frequency word, and the unknown word.  FIG. 8A  is a diagram schematically illustrating the procedure for compressing the high frequency word.  FIG. 8A  exemplifies a case in which the extraction unit  50  extracts “a” from the compression target file  32 . The determination unit  51  collates “a” with the static dictionary  34 , and determines whether “a” is the high frequency word, the low frequency word, or the unknown word. The compressed code for “a” is registered in the item of “static code”. Thus, “a” is determined to be the high frequency word. The replacement unit  52  replaces “a” with the compressed code “4000h” in the item of “static code”. The generation unit  53  stores the compressed code “4000h” in the compressed file  33 . 
         [0079]      FIG. 8B  is a diagram schematically illustrating the procedure for compressing the low frequency word.  FIG. 8B  exemplifies a case in which the extraction unit  50  extracts “abject” from the compression target file  32 . The determination unit  51  collates “abject” with the static dictionary  34 , and determines whether “abject” is the high frequency word, the low frequency word, or the unknown word. No compressed code for “abject” is registered in the item of “static code”, and no compressed code therefor is registered in the item of “dynamic code”. Thus, “abject” is determined to be the low frequency word. The replacement unit  52  assigns a new compressed code “A000h” to “abject”. The replacement unit  52  replaces “abject” with the assigned compressed code “A000h”. The replacement unit  52  registers the basic code “A0002Ch” of “abject” in the buffer part  31 C. The replacement unit  52  registers the assigned compressed code “A000h” in the item of “dynamic code” of the pointer part  31 B, registers “1” in the item of “classification”, and registers, in the item of “pointer”, the pointer indicating the position of the basic code “A0002Chh” stored in the buffer part  31 C. The replacement unit  52  registers the length of the basic code “A0002Ch” in the item of “length” of the pointer part  31 B, and registers the initial value “000000h” in the item of “preliminary code”. The replacement unit  52  registers the assigned compressed code “A000h” in the item of “dynamic code” of the record of “abject” in the static dictionary  34 . The generation unit  53  stores the compressed code “A000h” in the compressed file  33 . After this, the low frequency word registered in the dynamic dictionary  31  is replaced with the compressed code registered in the static dictionary  34  similarly to the high frequency word. 
         [0080]      FIG. 8C  is a diagram schematically illustrating the procedure for compressing the unknown word.  FIG. 8C  exemplifies a case in which the extraction unit  50  extracts “Mickey” from the compression target file  32 . The determination unit  51  collates “Mickey” with the static dictionary  34 , and determines whether “Mickey” is the high frequency word, the low frequency word, or the unknown word. “Mickey” is not registered in the static dictionary  34 . Thus, “Mickey” is determined to be the unknown word. The replacement unit  52  assigns a new compressed code “A001h” to “Mickey”. The replacement unit  52  replaces “Mickey” with the assigned compressed code “A001h”. The replacement unit  52  registers “Mickey” in the buffer part  31 C. The replacement unit  52  registers the assigned compressed code “A001h” in the item of “dynamic code” of the pointer part  31 B, registers “2” in the item of “classification”, and registers, in the item of “pointer”, the pointer indicating the position of “Mickey” stored in the buffer part  31 C. The replacement unit  52  registers the length of “Mickey” stored in the buffer part  31 C in the item of “length” of the pointer part  31 B, and registers the initial value “000000h” in the item of “preliminary code”. The replacement unit  52  registers the pointer toward “A001h” in the item of “pointer” of the record of the 2-gram character in the dynamic bit filter part  31 A corresponding to “Mickey”. The generation unit  53  stores the compressed code “A001h” in the compressed file  33 . After this, the unknown word registered in the dynamic dictionary  31  is replaced with the compressed code registered in the dynamic dictionary  31 . 
         [0081]    After storing the compressed codes for all of the words, the generation unit  53  stores the dynamic dictionary  31  in the trailer of the compressed file  33  and generates the compressed file  33 . In  FIGS. 8A to 8C , the dynamic dictionary  31  is stored in the trailer of the compressed file  33 . 
         [0082]    The following describes a configuration of the server device  11 .  FIG. 9  is a diagram illustrating an example of the configuration of the server device. The server device  11  is a device that performs coding such as decoding of the compressed file  33 . The server device  11  is, for example, an information processing device such as a personal computer and a server computer constituting a cloud system. As illustrated in  FIG. 9 , the server device  11  includes a memory unit  60  and a control unit  61 . The server device  11  may include units other than the above-described units included in the information processing device. 
         [0083]    The memory unit  60  is a storage device such as a hard disk, an SSD, and an optical disc. The memory unit  60  may be a data-rewritable semiconductor memory such as a RAM, a flash memory, and an NVSRAM. 
         [0084]    The memory unit  60  stores an OS and various programs to be executed by the control unit  61 . For example, the memory unit  60  stores various programs for performing replacement processing and decoding processing described later. The memory unit  60  further stores various pieces of data used in the program executed by the control unit  61 . For example, the memory unit  60  stores the standard dictionary  30 , an extension dictionary  71 , the compressed file  33 , and a decoded file  72 . 
         [0085]    The standard dictionary  30  is dictionary data used for compressing and decoding data. The standard dictionary  30  is the same as the standard dictionary  30  in the terminal device  10 , so that the description thereof will not be repeated. 
         [0086]    The extension dictionary  71  is dictionary data storing additional information of the basic word stored in the standard dictionary  30  and various pieces of information about a word other than the basic word stored in the standard dictionary  30 . For example, in the extension dictionary  71 , the compressed code and the basic code are defined for a new word other than the basic word, and various pieces of information such as a part of speech that can be utilized for data mining for each of the basic word and the new word are stored. The extension dictionary  71  may be one dictionary, or may include a plurality of dictionaries. In the present embodiment, the standard dictionary  30  and the extension dictionary  71  function as the large-scale dictionary  70 . For example, as schematically illustrated in  FIG. 2 , the basic code is defined for a word, and a compressed code is registered for a high frequency word in the large-scale dictionary  70 . The part of speech of each word is registered in the large-scale dictionary  70 . 
         [0087]    The compressed file  33  is data on which compression processing is performed by the terminal device  10 . The decoded file  72  is data obtained by decoding the compressed file  33 . 
         [0088]    The control unit  61  is a device that controls the server device  11 . As the control unit  61 , an electronic circuit such as a CPU and an MPU, and an integrated circuit such as an ASIC and an FPGA can be employed. The control unit  61  includes programs specifying various processing procedures and an internal memory for storing control data, and performs various types of processing using the programs and the internal memory. The control unit  61  functions as various processing units when various programs operate. For example, the control unit  61  includes a replacement unit  80  and a decoding unit  81 . 
         [0089]    The replacement unit  80  performs replacement on the dynamic dictionary  31  stored in the trailer of the compressed file  33 . The replacement unit  80  includes a determination unit  82  and a storage unit  83 . 
         [0090]    The determination unit  82  determines whether the word registered in the dynamic dictionary  31  that is stored in the trailer of the compressed file  33  is registered in the large-scale dictionary  70 . For example, the determination unit  82  refers to the pointer part  31 B, and reads out data corresponding to the length from the position in the buffer part  31 C indicated by the pointer of classification “2”. Thus, the character string of the unknown word registered in the dynamic dictionary  31  is read out. The determination unit  82  compares the character string of the read unknown word with the word registered in the large-scale dictionary  70 , and determines whether the read unknown word is registered in the large-scale dictionary  70 . 
         [0091]    As a result of determination performed by the determination unit  82 , if the character string of the unknown word is registered in the large-scale dictionary  70 , the storage unit  83  stores, in the dynamic dictionary  31 , a code registered in the large-scale dictionary  70  in accordance with the character string of the unknown word. For example, the storage unit  83  stores the basic code registered in the large-scale dictionary  70  in accordance with the character string of the unknown word, in the preliminary code of the pointer part  31 B of the dynamic dictionary  31  stored in the trailer of the compressed file  33 . 
         [0092]    Accordingly, while keeping a state in which the compressed file  33  is compressed, the replacement unit  80  can associate the unknown word included in the compressed file  33  with the large-scale dictionary  70 . Due to this, the server device  11  can perform various types of processing such as data mining on the compressed data compressed into the compressed file  33  including the unknown word, and can cause the compressed data compressed into the compressed file  33  to be utilized more effectively. 
         [0093]    The decoding unit  81  decodes the compressed file  33 . The decoding unit  81  sequentially reads out the compressed codes stored in the compressed file  33 . The decoding unit  81  decodes the read compressed codes in order of words using the decoding dictionary  35  of the standard dictionary  30  and the dynamic dictionary  31  stored in the trailer of the compressed file  33 . 
         [0094]    The following describes a procedure for decoding the high frequency word, the low frequency word, and the unknown word.  FIG. 10A  is a diagram schematically illustrating the procedure for decoding the high frequency word.  FIG. 10A  exemplifies a case in which the decoding unit  81  reads out the compressed code “4000h” from the compressed file  33 . The decoding unit  81  collates the compressed code “4000h” with the decoding dictionary  35 , and stores the word “a” corresponding to “4000h” in the decoded file  72 . 
         [0095]      FIG. 10B  is a diagram schematically illustrating the procedure for decoding the low frequency word. FIG.  10 B exemplifies a case in which the decoding unit  81  reads out the compressed code “A000h” from the compressed file  33 . The decoding unit  81  collates the compressed code “A000h” with the pointer part  31 B, and reads out data corresponding to the length from the position in the buffer part  31 C indicated by the pointer to acquire the basic code “A0002Ch” corresponding to the compressed code “A000h”. The decoding unit  81  collates the basic code “A0002Ch” with the decoding dictionary  35 , and stores the word “Abject” corresponding to “A0002Ch” in the decoded file  72 . 
         [0096]      FIG. 10C  is a diagram schematically illustrating the procedure for decoding an unknown word.  FIG. 10C  exemplifies a case in which the decoding unit  81  reads out the compressed code “A001h” from the compressed file  33 . The decoding unit  81  collates the compressed code “A001h” with the pointer part  31 B, and reads out data corresponding to the length from the position in the buffer part  31 C indicated by the pointer to acquire the character string “Mickey”. The decoding unit  81  then stores the character string “Mickey” in the decoded file  72 . 
         [0097]    Processing Procedure 
         [0098]    The following describes a procedure of compression processing in which the terminal device  10  according to the present embodiment encodes and compresses the compression target file  32 .  FIG. 11  is a flowchart illustrating an example of a process of compression processing. The compression processing is performed at a predetermined timing, for example, a timing when a predetermined operation is performed for designating the compression target file  32  and instructing compression start. 
         [0099]    As illustrated in  FIG. 11 , the extraction unit  50  extracts the character string from the compression target file  32  in units of a word (Step S 10 ). The determination unit  51  collates the extracted word with the static dictionary  34 , and determines whether the word is registered in the static dictionary  34  (Step S 11 ). If the word is not registered (No at Step S 11 ), the replacement unit  52  regards the extracted word as an unknown word, and determines whether the word is registered in the dynamic dictionary  31  (Step S 12 ). If the extracted word is registered in the dynamic dictionary  31  (Yes at Step S 12 ), the determination unit  51  replaces the extracted word with the compressed code registered in the dynamic dictionary  31  (Step S 13 ). 
         [0100]    If the unknown word is not registered in the dynamic dictionary  31  (No at Step S 12 ), the replacement unit  52  regards the extracted word as the unknown word not registered in the dynamic dictionary  31 , dynamically assigns a new 3-byte compressed code to the extracted word, and replaces the extracted word with the assigned compressed code (Step S 14 ). The replacement unit  52  associates the character string of the extracted word, the dynamically assigned compressed code, and the region for the preliminary code with each other, and stores them in the dynamic dictionary  31  (Step S 15 ). 
         [0101]    If the word is registered (Yes at Step S 11 ), the replacement unit  52  determines whether the compressed code is stored in the item of “static code” (Step S 16 ). If the compressed code is stored in the item of “static code” (Yes at Step S 16 ), the determination unit  51  regards the extracted word as the high frequency word, and replaces the extracted word with the compressed code stored in the item of “static code” (Step S 17 ). 
         [0102]    If the compressed code is not stored in the item of “static code” (No at Step S 16 ), the determination unit  51  determines whether the compressed code is stored in the item of “dynamic code” (Step S 18 ). If the compressed code is not stored in the item of “dynamic code” (No at Step S 18 ), the determination unit  51  regards the extracted word as the low frequency word not registered in the dynamic dictionary  31 , dynamically assigns a new 3-byte compressed code to the extracted word, and replaces the extracted word with the assigned compressed code (Step S 19 ). The replacement unit  52  associates the basic code of the extracted word, the dynamically assigned compressed code, and the region for the preliminary code with each other, and stores them in the dynamic dictionary  31  (Step S 20 ). 
         [0103]    If the compressed code is stored in the item of “dynamic code” (Yes at Step S 18 ), the determination unit  51  regards the extracted word as the low frequency word registered in the dynamic dictionary  31 , and replaces the extracted word with the compressed code in the item of “dynamic code” (Step S 21 ). 
         [0104]    The generation unit  53  sequentially stores replaced compressed codes in the compressed file  33  (Step S 22 ). The extraction unit  50  determines whether extraction of all the words in the text data from the compression target file  32  is completed (Step S 23 ). If extraction of all of the words is not completed (No at Step S 23 ), the process proceeds to Step S 10  described above. 
         [0105]    If extraction of all of the words is completed (Yes at Step S 23 ), the generation unit  53  stores the dynamic dictionary  31  in the compressed file  33  (Step S 24 ), and ends the process. 
         [0106]    Next, the following describes a process of replacement processing in which the server device  11  according to the present embodiment performs replacement on the dynamic dictionary  31  stored in the trailer of the compressed file  33 .  FIG. 12  is a flowchart illustrating an example of the process of replacement processing. The replacement processing is performed at a predetermined timing, for example, a timing when the compression target file  32  is stored in the server device  11 . The replacement processing may be performed at a timing when a predetermined operation is performed for designating the compressed file  33  and instructing replacement start. The replacement processing may also be performed at a timing corresponding to decoding processing, for example, before or after the decoding processing described later. 
         [0107]    As illustrated in  FIG. 12 , the determination unit  82  refers to the pointer part  31 B of the dynamic dictionary  31  stored in the trailer of the compressed file  33 , and sequentially reads out the character string of the unknown word corresponding to the length from the position in the buffer part  31 C indicated by the pointer of classification “2” (Step S 50 ). The determination unit  82  compares the read character string of the unknown word with the word registered in the large-scale dictionary  70 , and determines whether the read unknown word is registered in the large-scale dictionary  70  (Step S 51 ). If the read character string of the unknown word is not registered in the large-scale dictionary  70  (No at Step S 51 ), the process proceeds to Step S 53  described later. 
         [0108]    If the read character string of the unknown word is registered in the large-scale dictionary  70  (Yes at Step S 51 ), the storage unit  83  stores, in the preliminary code of the pointer part  31 B of the dynamic dictionary  31 , the basic code registered in the large-scale dictionary  70  in accordance with the character string of the unknown word (Step S 52 ). 
         [0109]    The determination unit  82  determines whether all of the character strings of the unknown words stored in the dynamic dictionary  31  are read out (Step S 53 ). If not all of the character strings are read out (No at Step S 53 ), the process proceeds to Step S 50  described above. If all of the character strings are read out (Yes at Step S 53 ), the process is ended. 
         [0110]    Next, the following describes a process of decoding processing in which the server device  11  according to the present embodiment decodes the compressed file  33 .  FIG. 13  is a flowchart illustrating an example of the process of decoding processing. The decoding processing is performed at a predetermined timing, for example, a timing when a predetermined operation is performed for designating the compressed file  33  and instructing decoding start. 
         [0111]    As illustrated in  FIG. 13 , the decoding unit  81  sequentially reads out the compressed codes stored in the compressed file  33  (Step S 100 ). The decoding unit  81  decodes the read compressed code in order of words using the decoding dictionary  35  of the standard dictionary  30  and the dynamic dictionary  31  stored in the trailer of the compressed file  33  (Step S 101 ). The decoding unit  81  stores the decoded word in the decoded file  72  (Step S 102 ). The decoding unit  81  determines whether all of the compressed codes stored in the compressed file  33  are read out (Step S 103 ). If not all of the compressed codes are read out (No at Step S 103 ), the process proceeds to Step S 100  described above. If all of the compressed codes are read out (Yes at Step S 103 ), the process is ended. 
       Advantageous Effects 
       [0112]    As described above, the terminal device  10  according to the present embodiment replaces the character string in the compression target file  32  registered in the static dictionary  34  with the code corresponding to the character string. The terminal device  10  assigns a new compressed code to the character string in the compression target file  32  not registered in the static dictionary  34 , associates the character string, the new compressed code, and the region for the preliminary code with each other and stores them in the dynamic dictionary  31 , and replaces the character string with the new compressed code. The terminal device  10  generates the compressed file  33  including the replaced compressed code and the dynamic dictionary  31 . Due to this, the terminal device  10  can store information to be associated with the character string and the compressed code in the region for the preliminary code in the dynamic dictionary  31  later, so that the compression target file  32  can be utilized more effectively. 
         [0113]    The server device  11  according to the present embodiment determines whether the character string of the unknown word is registered in the large-scale dictionary  70 , the character string of the unknown word being stored in the dynamic dictionary  31  of the compressed file  33  while being associated with the compressed code and the region for the preliminary code. If the character string is registered in the large-scale dictionary  70 , the server device  11  stores, in the region for the preliminary code in the dynamic dictionary  31 , the basic code corresponding to the character string of the unknown word in the large-scale dictionary  70 . Accordingly, the server device  11  can associate the character string of the unknown word with the basic code of the large-scale dictionary  70  without decoding the compression target file  32 . 
       [b] Second Embodiment 
       [0114]    The embodiment of the disclosed device has been described above. However, the disclosed technique may be implemented in various different forms other than the embodiment described above. The following describes another embodiment encompassed by the present invention. 
         [0115]    For example, in the above embodiment, regarding the character string of the unknown word not registered in the standard dictionary  30 , “000000h” indicating that the preliminary code is not set is stored in the region of “preliminary code” of the pointer part  31 B of the dynamic dictionary  31  in compression processing. However, the embodiment is not limited thereto. For example, in compression processing, when the information corresponding to the character string of the unregistered unknown word is registered in another dictionary even if the unknown word is not registered in the standard dictionary  30 , the information corresponding to the character string of the unregistered unknown word may be stored in the region of “preliminary code” of the pointer part  31 B of the dynamic dictionary  31 .  FIG. 14  is a diagram schematically illustrating the procedure of compression processing.  FIG. 14  exemplifies a case in which the server device  11  compresses “ . . . a pen . . . Mickey . . . ” included in the compression target file  32 . The word “Mickey” is not registered in the standard dictionary  30 , but the basic code thereof is registered in the extension dictionary  71 . Thus, the basic code “AFFFFFh” is registered in the large-scale dictionary  70  corresponding to “Mickey”. The server device  11  compresses “Mickey” as the character string of the unknown word not registered in the standard dictionary  30  so as to enable decoding by the terminal device  10  including only the standard dictionary  30 . However, if the character string not registered in the standard dictionary  30  is registered in another dictionary included in the server device  11 , the server device  11  stores, in the region of “preliminary code”, the code corresponding to the unregistered character string in the other dictionary. For example, the server device  11  stores the basic code “AFFFFFh” in the region of “preliminary code” of the pointer part  31 B of the dynamic dictionary  31 . The server device  11  may store, in the region of “preliminary code” of the pointer part  31 B of the dynamic dictionary  31 , information related to the unregistered character string such as the compressed code in the large-scale dictionary  70  or information indicating the part of speech in addition to the basic code. Accordingly, the server device  11  can compress the compression target file  32  using the information of the large-scale dictionary  70 , and can perform various types of processing such as data mining while keeping a state in which the compressed file  33  is compressed including the character string not registered in the standard dictionary  30 . The compressed file  33  can also be decoded by the terminal device  10  including only the standard dictionary  30  because the character string not registered in the standard dictionary  30  is registered in the dynamic dictionary  31 . 
         [0116]    In the above embodiment, the compressed file  33  stores the dynamic dictionary  31  including the region of “preliminary code” of the pointer part  31 B in compression processing. However, the embodiment is not limited thereto. In compression processing, the dynamic dictionary  31  may be stored in the compressed file  33  without providing the region of “preliminary code” to the pointer part  31 B, and the region of “preliminary code” may be added to the pointer part  31 B of the dynamic dictionary  31  in the compressed file  33  later. For example, the terminal device  10  stores the dynamic dictionary  31  in the compressed file  33  without providing the region of “preliminary code” to the pointer part  31 B. The server device  11  checks whether there is the region of “preliminary code” in the pointer part  31 B of the dynamic dictionary  31  in the compressed file  33  at a predetermined timing such as a timing when the compressed file  33  is received or a timing for decoding. If the region of “preliminary code” is not included in the pointer part  31 B of the dynamic dictionary  31  in the compressed file  33 , the server device  11  may add the region of “preliminary code” to the pointer part  31 B. 
         [0117]    The components of the devices illustrated in the drawings are merely conceptual, and it is not required that it is physically configured as illustrated necessarily. That is, specific forms of distribution and integration of the devices are not limited to those illustrated in the drawings. All or part thereof may be functionally or physically distributed/integrated in optional units depending on various loads or usage states. For example, the processing units, namely, the extraction unit  50 , the determination unit  51 , the replacement unit  52 , and the generation unit  53  of the terminal device  10  may be appropriately integrated. The processing units, namely, the replacement unit  80  (the determination unit  82 , the storage unit  83 ) and the decoding unit  81  of the server device  11  may be appropriately integrated. The processing performed by each of the processing units of the terminal device  10  and the server device  11  may be appropriately separated into pieces of processing performed by a plurality of processing units. All or any part of processing functions executed by the processing units may be implemented by a CPU and a computer program to be analyzed and executed by the CPU, or may be implemented as hardware based on wired logic. 
         [0118]    Compression Program 
         [0119]    The various types of processing described in the above embodiments can also be performed by executing a computer program prepared in advance with a computer system such as a personal computer and a workstation. The following describes an example of a computer system that executes a computer program having the same function as that in the above embodiments. First, the following describes a compression program for performing compression processing.  FIG. 15  is a diagram illustrating an example of a computer that executes the compression program. 
         [0120]    As illustrated in  FIG. 15 , a computer  400  includes a central processing unit (CPU)  410 , a hard disk drive (HDD)  420 , and a random access memory (RAM)  440 . These components  400  to  440  are connected to each other via a bus  500 . 
         [0121]    The HDD  420  includes a compression program  420   a  stored therein that exhibits a function similar to the extraction unit  50 , the determination unit  51 , the replacement unit  52 , and the generation unit  53  in the terminal device  10 . The compression program  420   a  may be appropriately divided into a plurality of parts. 
         [0122]    The HDD  420  stores various pieces of information. For example, the HDD  420  stores an OS and various pieces of data used for compression. 
         [0123]    When the CPU  410  reads out the compression program  420   a  from the HDD  420  and executes it, the same operation as that of each processing unit according to the embodiments is performed. That is, the compression program  420   a  performs the same operation as that of the extraction unit  50 , the determination unit  51 , the replacement unit  52 , and the generation unit  53 . 
         [0124]    The compression program  420   a  is not necessarily stored in the HDD  420  from the beginning. 
         [0125]    Replacement Program 
         [0126]    The following describes a replacement program that performs replacement on the dynamic dictionary  31  stored in the trailer of the compressed file  33 .  FIG. 16  is a diagram illustrating an example of a computer that executes the replacement program. The same component as that in  FIG. 15  is denoted by the same reference numeral, and the description thereof will not be repeated. 
         [0127]    As illustrated in  FIG. 16 , the HDD  420  includes a replacement program  420   b  stored therein that exhibits a function similar to the replacement unit  80  (the determination unit  82 , the storage unit  83 ) of the server device  11 . The replacement program  420   b  may be appropriately divided into a plurality of parts. The replacement program  420   b  may be a decoding program having the function of the decoding unit  81 . 
         [0128]    The HDD  420  stores various pieces of information. For example, the HDD  420  stores an OS and various pieces of data used for replacement. 
         [0129]    When the CPU  410  reads out the replacement program  420   b  from the HDD  420  and executes it, the same operation as that of each processing unit according to the embodiments is performed. That is, the replacement program  420   b  performs the same operation as that of the replacement unit  80 . 
         [0130]    The replacement program  420   b  is not necessarily stored in the HDD  420  from the beginning. 
         [0131]    For example, the compression program  420   a  and the replacement program  420   b  may be stored in a “portable physical medium” such as a flexible disk (FD), a CD-ROM, a DVD disc, a magneto-optical disc, and an IC card to be inserted into the computer  400 . The computer  400  may read out the program from such a medium and execute the program. 
         [0132]    Alternatively, the program may be stored in “another computer (or a server)” connected to the computer  400  via a public network, the Internet, a LAN, and a WAN. The computer  400  may read out the program from such a computer and execute the program. 
         [0133]    According to an aspect of the invention, compressed data can be utilized more effectively. 
         [0134]    All examples and conditional language recited herein are intended for pedagogical purposes of aiding the reader in understanding the invention and the concepts contributed by the inventor to further the art, and are not to be construed as limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.