Patent Publication Number: US-2019182356-A1

Title: Data networking method in data-centric network system and apparatus implementing same

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Korean Patent Application No. 10-2017-0168717, filed Dec. 8, 2017, the entire content of which is incorporated herein for all purposes by this reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a network system. Particularly, the present invention relates to a networking method of performing functional data processing in a data-centric network system in which both a pull mode and a push mode are supported. Also, the present invention relates to a network system including a user terminal and a network node to perform the functional data processing. 
     2. Description of Related Art 
     Recently, the era of ultra-connection has come, in which everything is connected. According to market research institutions, it is expected that more than several tens of billions of things are connected in 2020. Also, by 2020, the amount of data is expected to increase exponentially every year, and it is thus heralded that we have entered the era of ultra-connection data. 
     However, if such a large amount of data is not efficiently managed, the value that may be derived from the data is not properly generated and it only takes up storage capacity. 
     Recently, various types of network technology research has been carried out to change the basic paradigm of networking and make data use efficient. In this regard, there is an information-centric networking method based on a pull mode in which required data is requested and fetched, for example, Named Data Networking (NDN) or information-centric networking (ICN). Also, there is a data publisher and subscriber-based networking method, such as Pursuit, in which when data is produced, the data is pushed to a network and to a user who requested the data. 
     Also, rather than in terms of simple data transfer, a Named Function Networking (NFN) method, which extends the concept of ICN, in which a data processing function for processing data is named and the processing required for data is specified before the data is actually fetched, has also proposed. 
     However, NFN also includes only the functional processing by the data requestor that requires data. Accordingly, a network protocol, in which the functional processing is included when a data producer publishes and provides data, and the user terminal supporting the same have not yet been proposed. 
     The foregoing is intended merely to aid in the understanding of the background of the present invention, and is not intended to mean that the present invention falls within the purview of the related art that is already known to those skilled in the art. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and the present invention is intended to propose a new network system and a data networking method and apparatus using the same. 
     Also, the present invention is intended to propose a network system and a network essential configuration apparatus in which both data transfer methods in a pull mode and a push mode are supported and depending on the needs of a data producer, it is possible to request data processing. 
     Also, the present invention is intended to propose a network system and a network essential configuration apparatus in which sovereignty of the data producer is ensured by performing data type and content processing and data access right control according to intent of the data producer. 
     Also, the present invention is intended to propose a user terminal and a node device that constitute a network system for achieving the above purposes. 
     Other objects and advantages of the present invention will be understood from the following descriptions and become apparent by the embodiments of the present invention. Also, it is understood that the objects and advantages of the present invention may be implemented by components defined in the appended claims or their combinations. 
     In order to achieve the above object, according to one aspect of the present invention, there is provided a data networking method in a data-centric network system, the method including: receiving a message containing a content function name and context meta information corresponding to function processing; performing filtering for each function element used in a content filtering table (CFT) by analyzing the context meta information; and performing the function processing specified for a content including the filtered function element. 
     Furthermore, the message may be at least one among a request message, a response message, a subscription message, and a publication message. 
     Furthermore, the request message, the subscription message, and the publication message may include content function name fields. 
     Furthermore, the publication message may include the content required to be published and function processing context information for the content. 
     Furthermore, the context meta information may be produced by a content producer that requests publication function processing. 
     In order to achieve the above object, according to another aspect of the present invention, there is provided a data network system including: a host terminal producing and transmitting a message containing a content function name and context meta information corresponding to function processing; a first node transmitting the message to a node that is capable of performing the function processing of a content required by the host terminal, from the message received from the host terminal; and a second node, on the basis of the function name and the context meta information, performing filtering for each function element and performing the function processing specified for the content including a filtered function element, after receiving the message from the first node or the host terminal. 
     Furthermore, the message produced by the host terminal may be at least one among a request message, a response message, a subscription message, and a publication message. 
     Furthermore, the request message, the subscription message, and the publication message may include content function name fields for the function processing. 
     Furthermore, the publication message may include the content required to be published and function processing context meta information for the content. 
     Furthermore, the context meta information may be produced by a content producer that requests publication function processing. 
     Furthermore, the second node may include a content processing unit that includes at least one function processing processor performing a content function processing operation. 
     Furthermore, the second node may further include: an interface receiving and transmitting the message and the content over a network; and a storage means for storing data or the content. 
     Furthermore, the second mode may further include a context filtering table (CFT) analyzing and filtering the function name and the context meta information. 
     Furthermore, the content filtering table (CFT) may be a table for each function requested by a content filtering pointer. 
     Furthermore, the second mode may further include a pending request table (PRT) including the context filtering pointer. 
     In order to achieve the above object, according to still another aspect of the present invention, there is provided a user terminal for a host in a data-centric network system, the user terminal including: a content production unit producing a content function name and context meta information corresponding to function processing according to a purpose of a content; a message processing unit producing a message appropriate for a format of a message type, which contains the content function name and the context meta information; and a communication unit transmitting the produced message over a network. 
     Furthermore, when the message type is a publication message, the context meta information for the function processing of a content producer may be included. 
     Furthermore, the user terminal may further include: a memory temporarily storing the content; and a user interface receiving a user command. 
     According to the embodiments of the present invention, both data transfer methods in the pull mode and the push mode are supported, and an appropriate data transfer method is possibly selected according to the characteristics of the application. 
     Also, depending on the needs of the data requester or the data user, it is possible to request function processing on the data, and the data producer can specify the processing function for the data even when publishing the data, whereby sovereignty of the data producer is ensured. 
     Also, data function processing of the data producer and requester or the user is possible through the network, so that the utilization value of a large amount of data that is present in the network may be further increased. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a diagram illustrating an example of a configuration of a data-centric network system applied to the present invention; 
         FIGS. 2A and 2B  are diagrams illustrating examples of a hierarchical naming method of a network data applied to the present invention; 
         FIGS. 3 to 6  are diagrams illustrating examples of four types of network data messages and information included in each message applied to the present invention; 
         FIG. 7  is a diagram illustrating an example of a detailed configuration of a user terminal of a data-centric network system according to the present invention; 
         FIG. 8  is a diagram illustrating an example of a detailed configuration of a designated DCN node (DDN) of a data-centric network system according to the present invention; 
         FIG. 9  is a diagram illustrating data input and output at the designated DCN node (DDN) of a data-centric network system according to the present invention; 
         FIG. 10  is a flowchart illustrating a process by the content request message in the data-centric network system of the present invention; and 
         FIG. 11  is a flowchart illustrating a process by the content publication message in the data-centric network system of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings such that the present invention can be easily embodied by those skilled in the art to which this present invention belongs. However, the present invention may be embodied in various different forms and should not be limited to the embodiments set forth herein. 
     In describing the embodiments of the present invention, if it is decided that the detailed description of known function or configuration related to the invention makes the subject matter of the invention unclear, the detailed description is omitted. Also, parts that are not related to the description of the present invention are omitted in the drawings, and like reference numerals designate like parts. 
     In the present invention, constituent elements that are distinguished from each other to clearly describe each feature do not necessarily denote that the constituent elements are separated. That is, a plurality of constituent elements may be integrated into one hardware or software unit, or one constituent element may be distributed into a plurality of hardware or software units. Accordingly, even if not mentioned, the integrated or distributed embodiments are included in the scope of the present invention. 
     In the present invention, constituent elements described in various embodiments do not denote essential elements, and some of the elements may be optional. Accordingly, an embodiment that includes a subset of constituent elements described in another embodiment is included in the scope of the present invention. Also, an embodiment that includes the constituent elements which are described in the various embodiments and additional other elements is also included in the scope of the present invention. 
     If necessary, data is used with a mix of content to describe the present invention, but these are just different expressions of the same object and technical meanings are not different. For example, “data” may be an expression of physical or objective meaning, and “content” may be an expression of subjective meaning. 
     Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. 
       FIG. 1  is a diagram illustrating an example of a configuration of a data-centric network system applied to the present invention. 
     The data-centric network (hereinafter, referred to as “a DCN”) according to the present invention has a structure in which data transfer methods in a pull mode and a push mode both are supported. That is, for example, like named data networking (NDN), the structure in which a network data transfer method that an interest packet for the content is transmitted and the content is received in response thereto and a publisher and subscriber based network data transfer method are applied simultaneously are described. 
     Also, according to the present invention, unlike the conventional ICN method in which data is received by requesting data processing depending on the needs of the content data user, the processing function for the data is specified when the data consumer makes a request and when the data producer publishes the data, so that processing of the data type, content, and the like, data access right control are performed according to intent of the data producer, thereby sovereignty of the data producer is ensured. 
     Referring to  FIG. 1 , the DCN according to the present invention includes, a DCN participating host  10 , which is the subject of content producing or content consuming, and two types of DCN nodes  20  and  30 . 
     The host  10  may be a data producer  11  that produces data, a data subscriber  12  that requests regular subscription or use of data, a data requester  13  that request specific data for data use, a data responder  14  that responds to the data request, and a data publisher  15  that performs publication and open of the produced data. However, the host  10  is arbitrarily divided according to a function, and it is possible that multiple functions or all functions are performed by a single terminal. In general, the host  10  may be referred to as a user terminal, and this will be described in detail with reference to  FIG. 7 . 
     A first node of the DCN nodes is a basic data node (BDN)  20  that receives the DCN message transmitted from the host  10  and is in charge of content publication and, storage or caching in the DCN. The BDN is also referred to as a first DCN node or a basic DCN, and corresponds to the modification of the DCN node used in the conventional data network. 
     A second node of the DCN nodes is a designated data node (DDN)  30  that is capable of performing processing such as data processing in response to the request from the BDN or the data producer  11 , publishing agent, content access control, and the like. The DDN is also referred to as a second DCN node or a special DCN node, and the DDN performs the function processing to achieve the purpose of the present invention. Hereinafter, configuration and operation of the DDN will be described in detail with reference to  FIGS. 8 to 11 . 
     In this regard, the DDN  30  may be present at an arbitrary location within the DCN, but in general, it is desirable that the BDN  20  is provided between the host  10  and the DDN  30  so as to reduce the load of the DDN in structure. However, the present invention is not limited thereto, and depending in the intention of the network system designer, it is possible to allow direct access to the DDN  30  from the host  10 , or to prevent the DDN having the same function from being duplicated, or to provide the DDN  30  at the optimum location within the network system by considering the location of the content producer  11 , publisher  15 , subscriber  12 , or requester  13  as the host  10  and the performance of the DDN  30 . 
       FIGS. 2A and 2B  are diagrams illustrating examples of a hierarchical naming method of a network data applied to the present invention. In the DCN according to the present invention, the content and the function are named and the content request and response based on the name are processed. 
     Also, regarding the name given to the content and the function, a public key hash value of the name owner is included in the name so that a flat address having a self-certifying ID without intervention of the trusted third party is given. 
     The present invention uses, for example, a hierarchical content name structure as shown in  FIG. 2A . The hierarchical content name structure of the data may be, for example, configured as “/etri/research/presentations/slide20/v=2/c=0”. In the name, the head “etri”  41  means a communication router address to which data is transmitted and is used as a globally common address. Also, “research/presentations/slide20/”  42  means a lower-layer application address within the relevant router address (“etri”  41 ) and means the location where actual data is present. Also, “v=2/c=0”  43  means protocol information for data communication. 
     Also, for example, the present invention may use a hierarchical function name structure shown in  FIG. 2B . The hierarchical function name structure of the data may be, for example, configured as “/func_name/func_args_hash”. That is, the names of the functions as shown in  FIG. 2B  includes: a globally routable function name  51  itself, and a hash  52  of information included in the meta information, such as a name of the host which requests the function, a session number within the host, and the like. It is possible to distinguish the same function request from multiple hosts or from other sessions of the same host. 
     Specifically, in the name, the head “/func_name”  51  means the name of the function to which the data is subjected. For example, functions such as data processing, publication, access control, and the like may be performed. These functions are managed as a network system standard, and the rule determined as a standard may be applied to each network participant, such as, the host  10 , the BDN  20 , and the DDN  30 . For example, the rule may be determined in a manner that “0001” is assigned as the function type for the processing function, “0010” is assigned as the function type for the publication function, and “0100” is assigned as the function type for the access control function. 
     Also, the tail “/func_args_hash”  52  of the hierarchical function name structure of the data is given as a hash value of the relevant function, which is also included in the header information. 
       FIGS. 3 to 6  are diagrams illustrating examples of four types of network data messages and information included in each message applied to the present invention. 
     The DCN according to the present invention provides, as described in  FIGS. 3 to 6 , four types of packets for transmitting and receiving the content. A first type is a content request message for requesting the content. A second type is a content subscription message for indicating intent to receive the content at a point in time when the content is available regardless of whether or that the actual data is currently present. A third type is a content response message corresponding to the content request message. A fourth type is a publication message for publishing the content to the user who has already requested subscription to the content or who will request it at a point in time in the future. 
       FIG. 3  is a diagram illustrating an example of a configuration of the content request message for requesting the content. Referring to  FIG. 3 , the content request message includes: a packet type field  401  indicating a message packet type (including at least a message version and a message size); a content name field  402  defining either a content name  402   a  or a function name  402   b  as a content name; and a meta information field  403  containing meta information on the content function processing. Also, the content request message may further include a selection field  404  defining user selections for the requested content and a guide field  405 . For example, in the content name field  402 , the function name of the function of “content request” is set, and in the relevant meta information field  403 , the detailed processing function for the requested content is described, such that content transmission corresponding to the request from the content requester is possible. 
     In this regard, the content name  402   a  or the function name  402   b  defined in the content name field  402  may be expressed by the content name or the function name of the hierarchical structure as described above with reference to  FIG. 2 . However, the present invention is not limited thereto, and is applicable to various methods of expressing the content name or the function name. 
     Also, the meta information field  403  includes context information of the content having the name other than the basic name (for example, the content name  402   a  or the function name  402   b ) in the content name field  402 . For example, the meta information field  403  may include, as context meta information related to the content requested to be subscribed, a function description, function parameters, and the like. 
     Here, the context means the content that is assigned differently depending on the temporal, spatial situations of elements, such as the data producer, the data consumer, the network node, and the like, which may affect production and consumption of data. The context information is used in indicating the content function when requesting the content and in filtering and selecting the relevant content. This context enables the content requester, subscriber, or publisher to explicitly specify the content when requesting the content in such a manner that contents of the same name having different contexts may be selectively received according to the context. 
     Also, when generating and publishing the content, a content provider (the content publisher targets the responder to the content request or an arbitrary subscriber) makes the context information of the relevant content to be included in such a manner that the content matching with the desired context is transmitted to the content receiver. 
       FIG. 4  is a diagram illustrating an example of a configuration of the subscription message for indicating intent to receive the content at a point in time when the content is available regardless of whether or that the actual data is currently present. Referring to  FIG. 4 , the content subscription message includes: a packet type field  501  indicating at least a message packet type (including at least a message version and a message size); a content name field  502  defining either a content name  502   a  or a function name  502   b  as a content name; and a meta information field  503  containing meta information on the content function processing. Also, the content request message may further include a selection field  504  defining user selections for the requested content and a guide field  505 . For example, in the content name field  502 , the function name of the function of “content subscription” is set, and in the relevant meta information field  503 , the detailed processing function for the requested content is described, such that content transmission corresponding to the request from the content subscriber is possible. 
     Regarding the subscription message, in addition to the message for subscription, a message type for canceling the subscription may be defined as a sub type. The sub-type message may be referred to as “a subscription cancellation message” to be distinguished from the subscription message. 
     For example, the meta information field  503  may include, as the context meta information related to the content requested to be subscribed, a function description, function parameters, and the like. 
       FIG. 5  is a diagram illustrating an example of a configuration of the content response message corresponding to the content request message shown in  FIG. 3 . Referring to  FIG. 5 , the content response message includes: a packet type field  601  indicating a message packet type (including at least a message version and a message size); a content name field  602  indicating the requested content name; and a meta information field  603  containing meta information on the content function processing. 
     Also, the content response message may include a content  604  transmitted in response to the requested content and may further include signature information  605  of the content transmitter. In this regard, in the content name field  602 , only the provided content name is indicated and the function name is not indicated. Also, the meta information field  603  may include, as the context meta information related to the provided content  604 , for example, the content type, the content production period, and the like. 
       FIG. 6  is a diagram illustrating an example of a configuration of a publication message for publishing the content to the user who has already requested subscription to the content or who will request it at a point in time in the future. Referring to  FIG. 6 , the content publication message includes: a packet type field  701  indicating a message packet type (including at least a message version and a message size); a content name field  702  defining either a content name  702   a  or a function name  702   b  as a content name; and a meta information field  703  containing meta information on the content function processing. For example, in the content name field  702 , the function name of the function of “content publication” is set, and in the relevant meta information field  703 , the detailed processing function for the content required to be published is described, such that content publication corresponding to the request from the content publisher is possible. 
     Also, the content publication message may include the content  704  requested to be published and may further include signature information  705  of the content publisher. 
     In this regard, the meta information field  703  may include, as context meta information related to the content  704  requested to be published, for example, the content type, the content production period, and the like. Also, optionally, the meta information field  703  may further include, for efficient publication function processing, the content name, function parameters, and the like. 
     In this regard, according to the present invention, among the messages shown in  FIGS. 3 to 6 , all the messages except for the response message shown in  FIG. 4  transmitted in response to the request message shown in  FIG. 3  are designated by “the function names”, which specifies the function processing for the content, rather than the content names, and the messages are directly transmitted to the DDN  30  that may process the function. Here, the function processing means all packet processing operations using the content, which include security function processing, such as processing for the content, and the filtering function for access control to the content. 
       FIG. 7  is a diagram illustrating an example of a detailed configuration of the user terminal  10  for the host of the data-centric network system according to the present invention. As described above, the user terminal  10  means a terminal that performs at least one of the functions of the hosts  11 ,  12 ,  13 ,  14 , and  15  in  FIG. 1  on the DCN of the present invention. 
     Referring to  FIG. 7 , the user terminal  10  includes a content production unit  104 , a content-name/function-name and context production unit  103 , a message processing unit  102 , and a communication unit  101 . Also, the user terminal  10  includes a display unit  105  for displaying content production, content name and context information production, and message processing. Also, the user terminal  10  may further include a memory  107  for temporarily storing the data and the content and a user interface  106  for receiving a user command. Also, the user terminal  10  may further include an RF module  108  having an antenna that communicates with the outside in cooperation with the communication unit  101 . 
     In this regard, when it is desired to transmit the message, the content-name/function-name or context production unit  103  produces the name and context information appropriate for the messages types shown in  FIGS. 3 to 6 , and the message processing unit  102  finally produces the message appropriate for the message type format shown in  FIGS. 3 to 6  and transmits the final message to the communication unit  101 . Here, in the case of “the response message shown in  FIG. 5 ” or “the publication message shown in  FIG. 6 ” which includes the content, it is possible to directly produce the content by the content production unit  104  or to use the content stored in the memory  107 . 
     In contrast, when receiving the message, the message received via the communication unit  101  is subjected to process appropriate to the purpose of the received message by the message processing unit  102 . 
       FIG. 8  is a diagram illustrating an example of a detailed configuration of the designated DCN node (DDN)  30  or the second node of a data-centric network system according to the present invention. 
     Referring to  FIG. 8 , the DDN  30  includes: an interface  34  performing data communication with the outside; and a storage unit  33  storing a program for the operation of the DDN  30 . Also, the DDN  30  may further include: a processor  31  performing efficient calculation and control within the node; and a memory  32  temporarily storing the data. 
     In this regard, communication schemes for the interface  34  include, for example, the Internet, wireless data communication, near field mobile communication Wi-Fi, and the like. Also, the interface  34  may include multiple interface ports or faces with respect to the same communication scheme. Each port or face of the interface is individually managed. 
     Also, the storage unit  33  includes: an operating system  331  having an overall operating system program for the DDN  30  thereon; a storage means  333  for storing data or contents; and a content processing unit  332  having multiple processors performing content function processing operations. Here, the multiple processors for processing the content functions include a content processing processor  3321 , a content publication processor  3322 , and a content access processor  3323 . However, it is obvious that there may be various function processing processors for processing functions of the present invention other than the above processors. 
     Hereinafter, a data or content function processing method using the DDN  30  will be described in detail with reference to  FIGS. 9 to 11 . 
       FIG. 9  is a diagram illustrating data input and output at the designated DCN node (DDN) of a data-centric network system according to the present invention. Particularly,  FIG. 9  shows a content forwarding structure according to the present invention. In this regard, the content forwarding structure shown in  FIG. 9  will be described mainly about the DDN  30 , and it is possible to configure the same structure in the BDN  20  except for the function processing process. 
     Referring to  FIG. 9 , according to the present invention, the packet forwarding of the DCN uses a stateful forwarding method. 
     For example, the process of processing the case in which the content consumer transmits the request message shown in  FIG. 3  or the subscription message shown in  FIG. 4  with the name of the content or of the processing function required for the content will be described. 
     The DDN  30  (or the BDN  20 ) that received the request message shown in  FIG. 3  or the subscription message shown in  FIG. 4  stores the interface to which the relevant corresponding message is input and checks whether the content corresponding to the relevant name is stored in a content storage  334 . 
     When the content is present in the content storage  334 , the packet is forwarded to an input interface. However, when the desired content is not present in the content storage  334 , a record  337   a  of the request based on the name is stored in a pending request table (PRT)  337  and the request message shown in  FIG. 3  or the subscription message shown in  FIG. 6  is forwarded with a forwarding information base (FIB)  335  operation. However, when the DDN  30  that received the message is appropriate for the content function processing, it is obvious that direct processing is performed without forwarding to other network nodes. The detailed function processing method of the DDN  30  will be described later. 
     When the request message or the subscription message is transmitted from another network, the content is transmitted along the path through which the request message or the subscription message is transmitted according to the PRT  337  of each node. Also, the transmitted content (for example, the reference numeral  334   a ) performs content caching in the convent storage  334  in such a manner than when the same content request is made in the future, the relevant node directly transmits the content. 
     In this regard, in the PRT  337 , the request message, such as an interest in a request-response type communication model, and the subscription message for a publication-subscription (pub/sub) service are considered. That is, for example, regarding the PRT entry  337   a  produced by the request message, when the requested content arrives and is forwarded, the relevant interface is deleted from the PRT entry. However, the subscription message is not deleted from the PRT until the subscription cancellation message arrives. 
     Also, only the input interface is stored with respect to the conventional content name. However, in the present invention, forwarding is filtered according to the context regardless of the same name in such a manner to consider the context with respect to the content having the same name. That is, for example, when the context for the content is included in the meta information field  403  or  503  of the request message or subscription message, the PRT  337  does not store the input interface for the content name and stores the field  337   b  indicating that context filtering is required with a point (cftptr) for the entry of the filtering table. 
     Accordingly, in the entries  336   a  and  336   b  of the relevant filtering table within the context filtering table (CFT)  336 , the input interface (requesting face) into which the request message or subscription message is input with the context as a key is stored. 
     When the input request message or subscription message is configured with the function name, the final destination of the relevant message is the particular DDN  30  capable of processing the function. If the DDN which has received the request message or subscription message first is capable of performing the relevant function processing, it performs the function processing by itself. 
     Hereinafter, with reference to  FIGS. 10 and 11 , the content function processing flowcharts using the DDN  30  will be described as follows. 
       FIG. 10  is a flowchart illustrating a process by the content request message in the data-centric network system of the present invention. 
     First, from the host (for example, the data requester  13 ) requesting the content, the request message shown in  FIG. 3  is received at step S 101 . The request message includes, as described above, the meta information for the function name and the function processing. In this case, the name of the request message is designated by the function name, and additional information (parameter information for the function processing, which includes the content name) for the function processing is included as the meta information. 
     It is checked whether the content related to the request message shown in  FIG. 3  is present locally within the DDN  30  at step S 102 . When the relevant content is present locally within the DDN  30  that received the message, the content is read from the content storage  334  and is registered in the PRT  337 . After, filtering for the function processing according to the CFT  336  is performed. 
     When the relevant content is not present locally, the request message for the relevant content is transmitted to another node at step S 104 , and then the content is received from another node at step S 105 , and the function processing is performed and forwarding is performed according to the PRT. 
     The content filtered through the CFT is subjected to the final function processing using any one of the function processing processors in the content processing unit  332  shown in  FIG. 8  at step S 106 . After, the final function-processed content is transmitted to the content requester at step S 107 . 
       FIG. 11  is a flowchart illustrating a process by the content publication message in the data-centric network system of the present invention. First, from the host (for example, the data publisher  15 ) requesting content publication, the publication message shown in  FIG. 5  is received at step S 201 . The publication message includes, as described above, the meta information for the function name and the function processing. In this case, the name of the publication message is designated by the function name, and additional information (the parameter information for the function processing, which includes the content name) for the function processing is included as the meta information. 
     The content for publication, which is included in the received publication message is stored in the content storage  334  and is registered in the PRT  337 . After, content filtering for the function processing according to the CFT  336  is performed at step S 202 . 
     After, the DDN  30  which received the publication message obtains function related information in the meta information included within the message and performs the function processing, and then the publication processor  3322  within the content processing unit  332  shown in  FIG. 8  is used to perform the final function processing at step  203 . After, the final function-processed content is published according to intent of the content publisher at step S 204 . 
     In this regard, the content filtering process using the PRT  337  and the CFT  336  will be descried as follows, for example. The content filtering table (CFT)  336  shown in  FIG. 9  is a table that is present individually for each entry of the PRT  337  which requires context filtering. Also, each CFT includes each piece of context information, for example, a bloom filter for each function element. 
     As described above, the context may be explicitly specified or may be dynamically determined according to the situation. As an embodiment of the present invention, assuming that the context is explicitly given, for example, two hosts, a host A and a host B, use “/etri/building7/sensors”  337   b  as the subscription message for the content. In this regard, classification into one context is possible, but different types of function elements (for example, sensor information) may be requested. For example, the host A may request either the temperature or the humidity as a function element, and the host B may request both the temperature and the humidity as function elements. The CFT distinguishes the function element to be filtered from the context information and uses it for content filtering. In the above example, the case in which the context information explicitly requested by each of the hosts A and B via the meta information field is transmitted has been described. However, as another embodiment, it is possible to determine the context using situation information independently recognized outside the host. 
     As described above, in the present invention, for configuring the new data-centric network system, the format for each message type, an operation in the user terminal, and an operation in the DDN have been described. The above-described method according to the present invention may be realized as a program and stored in a computer-readable form in a recording medium (for example, a CD-ROM, a RAM, a ROM, a floppy disk, a hard disk, a magneto-optical disk, and the like). Since such processes can be easily embodied by those skilled in the art to which the present invention belongs, the detailed description thereof will be omitted. 
     Various substitutions, modifications, and changes from the spirit of the present invention defined in the following claims by those skilled in the art are also included in the scope of the present invention, so that the present invention described above is not limited to the embodiments and the accompanying drawings.