Abstract:
Disclosed is a method of building a personal network in a proxy server. The method includes building the personal network by registering information about a plurality of communication terminals in the proxy server through communication with the communication terminals, searching for a resource requested by a user terminal registered in the personal network, and sharing the found resource with the user terminal. The method allows a user to use own resource possessed by the user if access to the personal network of the user is possible.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit under 35 U.S.C. §119(a) of Korean Patent Application No. 10-2008-0127957, filed on Dec. 16, 2008, the disclosure of which is incorporated by reference in its entirety for all purposes. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The following description relates to a resource sharing technology based on a network, and more particularly, to a technology used to share resource such as files or video streaming data in a distributed computing environment. 
         [0004]    2. Description of the Related Art 
         [0005]    With the development of communication terminal technologies, most users generally possess or use one or more devices including an office computer, and a mobile terminal such as a mobile phone in addition to a home computer. However, possession of such devices does not guarantee access to them at all times. That is, if the user is present in a location remote from a user device, the contents stored and generated in the user device are not available to the user. Such a problem needs to be seriously considered when building a ubiquitous environment. This is because the ubiquitous environment needs to provide a user with unlimited access to resources regardless of time and place. 
         [0006]    Meanwhile, conventional personal network technologies have been mainly developed based on methods of searching for personal equipment around the user and controlling devices around the user. In addition, the conventional personal network technologies also include a method of sharing personal resources through sharing of a personal network folder or through a file sharing agent. In the personal resource sharing method through sharing of the personal network folder, which is regarded as the easiest method of sharing user resources, the user need to access a shared remote network folder to use files stored in the corresponding folder. In addition, according to the method of sharing resources using the file sharing agent, when a predetermined resource is required, a file sharing agent system is operated such that corresponding files are selected and transferred. However, the technologies described above only regard file sharing. 
       SUMMARY 
       [0007]    Accordingly, in one aspect, there is provided a method of building a personal network, allowing a user to search for or control resources regardless of a physical location of communication devices such as a computer or a storage possessed by the user, as if all of resources stored in the devices are stored in a local storage, if access to a network of the user is possible. 
         [0008]    In other aspect, there is provided a method of extending a range of a personal network by sharing the personal network with other user instead of exclusively possessing the personal network. 
         [0009]    In one general aspect, there is provided a method of building a personal network in a proxy server. The method includes building the personal network by registering information about a plurality of communication terminals in the proxy server through communication with the communication terminals; searching for a resource requested by a user terminal registered in the personal network; and sharing the found resource with the user terminal. 
         [0010]    The searching for the resource includes searching for a communication terminal storing the requested resource among the registered communication terminals. 
         [0011]    The searching for the resource further includes checking if the user terminal is authorized to search for the resources; receiving a resource request from the user terminal if the user terminal is authorized to search for the resource; and searching for the communication terminal storing the requested resource among the registered communication terminals. 
         [0012]    In another general aspect, there is provided a method of building a network federation in a proxy server for a personal network. The method includes building the personal network by registering information about a plurality of communication terminal in the proxy server through communication with the communication terminals; building a part of the network federation by registering information about the proxy server in a management server to build the network federation; receiving a resource request, which is generated by a user terminal belonging to another personal network of the personal network; searching for the requested resource in the personal network; and sharing the found resource with the user terminal of the another personal network. 
         [0013]    The method further includes searching for the resource, which is requested by a user terminal in the personal network; and transferring a request to the management server such that the resource is searched in the network federation except for the personal network, if the resource requested by the user terminal is not found in the personal network. 
         [0014]    In another general aspect, there is provided a method of building a network federation in a management server to federate personal networks. The method includes building the network federation by registering a plurality of proxy servers in the management server through communication with the proxy servers, in which a plurality of communication terminals are respectively registered in the proxy servers to build individual personal networks; receiving a resource search request which is generated by a user terminal and transferred through one of the proxy servers; and transferring the resource search request to another proxy server such that the another proxy server searches for a communication terminal storing the requested resource and allows the found resource to be shared with the user terminal. 
         [0015]    In another general aspect, there is provided a proxy server. The proxy server includes a storage and a controller. The storage stores information used to check an authority of a user and stores a list of resources of communication terminals registered in the proxy server. The controller operates such that the personal network is built by registering information about the communication terminals in the proxy server through communication between the communication terminals and the proxy servers, a user terminal requesting for registration is registered in the proxy server by checking the authority of the user terminal with reference to the storage, a communication terminal retaining a resource requested by the registered user terminal is searched in the registered communication terminals in response to a resource request from the user terminal, and the requested resource retained in the found communication terminal is transferred to the user terminal. 
         [0016]    The proxy server includes a data input/output unit to input and output data; and a format converter to convert a resource, which has been input to the input/output unit from the found communication terminal, in a format usable in the user terminal and then output the converted resource to the input/output unit. 
         [0017]    In another general aspect, there is provided a network federation system. The network federation system includes: a plurality of proxy servers to build a plurality of personal networks by registering information about the communication terminals through communication with the communication terminals; and a management server to build a network federation by registering information about the proxy servers through communication with the proxy servers; wherein each proxy server searches for a communication terminal having a resource requested by a user terminal among the communication terminal registered in the network thereof in response to the resource request from the user terminal, and if the proxy server fails to find the communication terminal having the requested resource, the proxy server requests the management server to search for the requested resource in the network federation except for the personal network which has been subject to the searching operation. The management server requests another proxy server to search for a communication terminal having the resource requested by the user terminal in response to the resource request from the proxy server. The another proxy server searches for a communication terminal having the requested resource in response to the resource request submitted by the management server and shares found resource with the user terminal. 
         [0018]    According to the present disclosure, the user can access the resource possessed by the user regardless of time and location, thereby enhancing the efficiency in use of resources. In addition, the resource possessed by the user can be shared with other users regardless of time and location. 
         [0019]    Accordingly, the personal network building method described above can be used when building a future oriented telecommuting environment, thereby achieving a green-IT. In addition, the personal network building method can be used to build a predetermined collaboration environment such as a military network and an administration network. In addition, the personal network building method can be used in an environment in which user devices lack storage space, for example, a ubiquitous environment. 
         [0020]    Other objects, features and advantages will be apparent from the following description, the drawings, and the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a conceptual diagram showing an exemplary personal network (PN); 
           [0022]      FIG. 2  is a conceptual diagram showing an exemplary personal network federation extended from a personal network; 
           [0023]      FIG. 3  is a view showing a data transmission model implemented in a personal network (PN) environment; 
           [0024]      FIG. 4  is a view showing a data transmission model implemented through a personal network proxy in a PN environment; 
           [0025]      FIG. 5  is a flow chart showing a resource sharing process in a PN environment; 
           [0026]      FIG. 6  is a flow chart showing operations of devices constituting the PN; 
           [0027]      FIG. 7  is a flow chart showing a resource sharing process in a personal network federation (PNF) environment; 
           [0028]      FIG. 8  is view showing a process of building a personal network federation (PNF); 
           [0029]      FIG. 9  is a flow chart showing devices constituting a PNF; 
           [0030]      FIG. 10  is a block diagram of a personal network (PN) system; 
           [0031]      FIG. 11  is a block diagram of a personal network federation (PNF) system; and 
           [0032]      FIG. 12  is a view showing a plurality of PNs constituting a PNF. 
       
    
    
       [0033]    Elements, features, and structures are denoted by the same reference numerals throughout the drawings and the detailed description, and the size and proportions of some elements may be exaggerated in the drawings for clarity and convenience. 
       DETAILED DESCRIPTION 
       [0034]    The following detailed description is provided to assist the reader in gaining a comprehensive understanding of the methods, apparatuses and/or systems described herein. Various changes, modifications, and equivalents of the systems, apparatuses and/or methods described herein will suggest themselves to those of ordinary skill in the art. Descriptions of well-known functions and structures are omitted to enhance clarity and conciseness. 
         [0035]    Abbreviations to be used throughout the specification are defined as follows:
       PN: Personal Network   PNP: PN Proxy   PNF: PN Federation   PNU: PN User   PN-Coordinator: Management Server for PNF   PD: Personal Device       
 
         [0042]      FIG. 1  is a conceptual diagram showing an exemplary personal network (PN). 
         [0043]    A PN  100  allows a person to use resources stored in various communication devices possessed by the person regardless of time and place. For example, a PN user  101  accesses the resources, for example, contents stored in the communication device located in a vehicle  102  of the PN user  101  by operating a mobile terminal carried by the PN user  101 . Further, the contents may be transferred and stored in a computer used in an office  103  of the PN user  101  ( 105 ). That is, even if the PN user  101  does not carry the communication device, the PN user  101  uses the resources stored in the communication devices possessed by the PN user  101  regardless of time and place by building a PN for all communication devices possessed by the PN user  101 . 
         [0044]      FIG. 2  is a conceptual diagram showing an exemplary personal network federation extended from a personal network. 
         [0045]    A plurality of PNs (PN# 1 , PN# 2 , PN# 3 , PN# 4 , . . . and PN#N) form a personal network federation (PNF)  200 . The PNF  200  is a network, which allows PN  202  possessed by PN users  201  to be shared with other users while providing an environment in which resources are shared between authorized PN users. The PNF  200  is aimed at allowing resources to be shared with other users. The use of the PNF  200  prevents redundant data from being stored by the PN users  201  or prevents the same resource from being repeatedly managed. Accordingly, the effective resource management can be achieved. In this regard, the sharing of resource is desirable. 
         [0046]    Meanwhile, a right of using resources is created in the PNF  200 , which is designed to enable a resource sharing between PN users. A user of resources such as files specifically creates a right of sharing the files of the user. The right of sharing resources is created such that the sharing of resources is applied to one PN user, a predetermined group of PN users, all PN users, or no PN users. 
         [0047]      FIG. 3  is a view showing a data transmission model implemented in a personal network (PN) environment. 
         [0048]    The data transmission model of a PNU# 1   307  and a PNU# 2   301  using contents stored in PDs  300  and  306  is described with reference to  FIG. 3 . If a plurality of PDs are distributed in a PN, information on the resources stored in the PDs and location information of the PDs are registered on a Personal Network Proxy (PNP)  302 . The registration of the information will be described later. When the PNU# 2   301  requests the PNP  302  ( 308 ) to provide resources, the PNP  302  searches for a PD  300 , which stores the requested resource, by using a resource cache  309  implemented in the PNP  302 . Names of resources and information regarding storage location of resources are stored in the resource cache  309 . The PNP  302  transmits a request for sharing of a resource to the found PD  300 , and informs the PNU# 2   301  of a result of the request. After that, the PD  300  transfers contents to the PNU# 2   301  by using location information of the PNU# 2   301  which is provided from the PNP  302  ( 304 ). 
         [0049]    Meanwhile, the PNP  302  supports the mobility of the PDs  300  and  306  and thus allows the PDs  300  and  306  to provide resources to the PNUs  301  and  307 , even when the PDs  300  and  306  move from a current network to another network. Since the PDs  300  and  306  continuously and periodically register location information on the PNP  302 , even if the PDs  300  and  306  change the locations, the PNP  302  allows resource sharing among the PNUs  301  and  307  and the PDs  300  and  306 . For example, even if the PD  305  moves from an office to home ( 305 - 1 ), the PNP  302  allows the moved PD  305  to keep providing services. 
         [0050]    Meanwhile, different from the service described above, a bi-directional data flow may be required depending on attributes of resources. For example, in the case of file editing, the transferring of resources between the PNU # 1   307  and the PD  306  may be realized in both directions ( 310 ). 
         [0051]    As an example of uni-directional resource transfer, in the case where a PNU requires a unidirectional resource transfer from a PD, the PNU requests the PD to provide a predetermined resource, such as video stream, and then receives the resource from the PD. As an example of bi-directional resource transfer, in the case where a PNU requires a bi-directional resource transfer with a PD, a packet is transmitted by the PNU and received by the PD, and vice versa. 
         [0052]      FIG. 4  is a view showing a data transmission model implemented through a personal network proxy in a PN environment. The data transmission model shown in  FIG. 4  is similar to that of  FIG. 3  except that resources stored in PDs  400  and  403  are indirectly transferred to PNUs through a PNP  406 . Such a function of indirectly transferring data needs to be performed in two cases. In the first case, the indirect transfer of data is required when the communication between a PD and a PNU is broken due to a firewall or a Network Address Translation (NET). In the second case, the indirect transfer of data is required when a format of resources stored in a PD does not match with a format of resources required by a PNU. 
         [0053]    As shown in  FIG. 4 , resources of the PDs  400  and  403  are indirectly transferred to PNUs  401  and  404  through the PNP  406  ( 402  and  405 ). The transferring of resources is performed through a uni-directional flow ( 402 ) or a bi-directional flow ( 405 ). Further, the PNP  406  may be provided with a temporary storage for storing frequently used data. 
         [0054]      FIG. 5  is a flow chart showing a resource sharing process in a PN environment. 
         [0055]    A PNU  500 , a PNP  501  and a PD  502  form a PN. The PNU  500  is a user who requests resources of the PN. In detail, the PNU  500  is a user terminal directly handled by a user. All services of the PN are performed based on the PNP  501 . To this end, the PD  502  forming the PN is registered in the PNP  501  (operation  503 ). A signaling for a resource sharing in the PN environment includes a request/reply operation. For example, in a registration (operation  503 ), if the PD  502  transmits a request for registration to the PNP  501 , the PNP  501  may accept the request of the PD  502 . Conversely, if the PNP  501  transmits a request for registration to the PD  502 , the PD  502  may accept the request of the PNP  501 . The registration process may be achieved in various fashions according to attributes and implementation schemes of the PD  502 . In the case that the PD has a computing function, the PD is actively registered in the PNP. As an example of the active registration, the PD is registered in the PNP at the same time with a booting of a computer. In the case that the PD is a passive device, the PNP is registered in PDs through a polling based on location information of the PDs preset in the PNP. A protocol used during such a signaling for registration may vary with an implementation scheme of the PN system. For example, the protocol may be a session initiation protocol (SIP). 
         [0056]    Meanwhile, after the registration has been completed, a list of resources stored in the PD  502  is provided to the PNP  501  (operation  504 ). The information on resources stored in the PD  502  is configured in the form of an identifier which is distinguishable in the PN. Only after an intention of involvement in the PNP  501  and a list of resources of the PDs  502  is submitted in the PNP  501 , the PNU  500  uses the resources in the PN. In order for the PNU  500  to use the resources of the PN, the PNU  500  needs to be registered in the PNP  501  (operation  505 ). 
         [0057]    The PNU  500  registered in the PNP  501  searches for required resources of the PN. The resources owned by the PNU  500  in the PN are searched through two schemes. The first scheme is performed when the PNU knows a location of the resources. If the PNU  500  knows that required resources ‘A’ are stored in a Personal Digital Assistant (PDA) owned by the PNU  500 , the PNU  500  requests the PNP  501  to provide the resources ‘A’ stored in the PDA. The second scheme is performed when the PNU does not know a location of the resources. In this case, the PNP  500  searches for required resources in the PN. 
         [0058]    In the searching for the resources of the PN, the PNU  500  requests the PNP  501  to search for a predetermined resource (operation  506 - 1 ). The PNP  501  inquires the PD  502 , which is founded from a catalog stored in the resource cache or a database (DB) of the PNP  501  or the list on the registered PD, if the required resources are stored in the PD  502  (operation  506 - 2 ). If the PD  502  has the required resources, the PD  502  distributes the resources to the PNU  500  seeking the resources (operation  507 ). The transmission characteristic of resources varies depending on attributes of the resources. For example, in the case of video streaming, resources may be transferred in one direction, and in the case of a file editing, resources may be transferred in two directions. After the PNU  500  has used the resources of the PN, the PNU  500  signs off from the PN (operation  508 ). 
         [0059]      FIG. 6  is a flow chart showing operations of devices constituting the PN. 
         [0060]    Interaction among devices including a PD, a PNP and a PNU will be described with reference to  FIG. 6 . The PD serves as a provider of resources, the PNU serves as a user of resources and the PNP serves as an agent between the PD and the PNU. The operations of a PNP need to precede the operations of a PN. After the PNP is initiated (operation  606 ), the PNP is registered (operation  607 ) and then enters a standby (operation  608 ). The registration is performed in a system environment such as a PNF environment, in which the registration of the devices is performed via a PN-Coordinator to be described later. If a system environment is configured by a single PN without a PN-Coordinator, the registration is not necessary. In the standby (operation  608 ), the PNP serves as an agent between the PD and the PNU. 
         [0061]    In a registration (operation  610 ) of the PD, the PD is registered in the PNP ( 602 ). In that case, the communication between the PD and the PNP is performed through a request/replay scheme and an active/passive manner. According to an exemplary implementation scheme, the PD may upload a list of available resources to the PNP. After the registration has been successfully completed, the PD enters a standby for providing a PN service (operation  603 ). 
         [0062]    The PNU requiring the resources is also subject to initiation (operation  609 ) and registration (operation  610 ). Since the PNU is accompanied by a user differently from the PD, the PNU may be registered in the PNP in an active manner (operation  611 ). After the registration of the PNU has been successfully completed, the PNU starts an operation, which is aimed to search for required resources (operation  612 ). The search operation forms a signal flow inquiring of the PNP regarding the required resources ( 613 ). Such a signal flow is transferred to the PD which has entered a standby ( 604 ). If the required resources are found, the PD enters a distribution (operation  605 ), so that contents of the PD are provided to the PNU ( 614 ). After that, the PNU enters a use of contents (operation  615 ) allowing the PD to use the contents provided from the PNU. After the distribution and use of the contents, the PNU and PD transit into the search (operation  612 ) and standby (operation  603 ) modes, respectively. 
         [0063]      FIG. 7  is a flow chart showing a resource sharing process in a personal network federation (PNF) environment. The resource sharing process shown in  FIG. 7  is similar to that of  FIG. 5  except that a plurality of PNs are united to configure a PNF. As shown in  FIG. 7 , the PNF is configured by adding a PN-Coordinators  702 . PNPs  701  and  703 , which have detected the existence of the PN-Coordinator  702 , are registered in the PN-Coordinator  702 , thereby informing the PN-Coordinator  702  of the existence of PNPs  701  and  703 (operations  705  and  706 ). In addition, a PD  704  is registered in the PNP  703  (operation  707 ) and enters a standby mode (operation  708 ). Accordingly, the registration and standby mode in a single PN is completed. 
         [0064]    In such a PNF environment, a PNU  700  requiring resources is registered in the PNP  701  of a PN to which the PNU  700  belongs (operation  709 ). After the PNU  700  has successfully performed the registration, the PNU  700  requests the PNP  701  to provide required resources through an inquiry (operation  710 ). The PNP  701  searches for the requested resources in the PN to which the PNU  700  belongs. If the requested resources do not exist in the PN, the PNP  701  requests the PN-Coordinator  702  to transfer a resource search inquiry to another PNP  703 , which forms the PNF in cooperation with the PNP  701  (operation  711 ). The PN-Coordinator  702  transfers the inquiry to the PNP  703  (operation  712 ), and the PNP  703  inquires of the PD  704  whether the PD  704  has the required resources (operation  713 ). According to an exemplary embodiment, the PN-Coordinator  703  has a capability of transferring an inquiry to all of the PNPs in the PNF. According to an exemplary embodiment, the PN-Coordinator may transfer the inquiry to all of the united PNPs. According to another exemplary embodiment, the PN-Coordinator may sequentially transfer an inquiry as follows. First, a PN-Coordinator transfers an inquiry for requesting resources to a PNP. If the PN-Coordinator receives a result of the inquiry indicating that the required resources do not exist in the PNP, the PN-Coordinator transfers an inquiry for requesting resources to another PNP. If it is found that the PD  704  has the required resources and the resources are allowed to be shared, the resources of the PD  704  are distributed to the PNU  700  requiring the resources (operation  714 ). After the use of the resource sharing service provided by the PNF, the PNU  700  signs off from the PN (operation  715 ). 
         [0065]    The PNP manages information described below, thereby providing the PN service to the PNU. 
         [0066]    1) PD information: ‘name of resources (title, contents tag)’, ‘location of resources including location of PD’ 
         [0067]    2) PNU information including authorization information: ‘user of resources’, ‘a person allowed to use resources’ and a handle used for adjusting the authorization of other user groups. 
         [0068]    3) Other information for defining characteristics of a PN provider Meanwhile, an authorization process and additional functions of the PD and PNU are performed when the PD and PNU are registered in the PNP. Similarly, an authorization process of the PNP is performed when the PNP is registered in the PN-Coordinator. According to an exemplary embodiment, the authorization is not important when a system environment is implemented as a single PN. However, in the case that a PNF is configured, the authorization is important in creating an authority of the PNU. That is, an additional signaling for the authorization is not important in a signaling flow for sharing resources. 
         [0069]      FIG. 8  is view showing a process of building a personal network federation (PNF). 
         [0070]    In order to build a PNF by uniting a plurality PNs, a PN-Coordinator  800  is required. PNPs  801  included in respective PNs form the PNF by performing a signaling with respect to the PN-Coordinator  800  ( 803 ). The PNF provides the PNU  802  with a transparency between PNs. As shown in  FIG. 8 , on the assumption that the PN-Coordinator  800  weaves a plurality of PNs into a single PN, the transparency represents that the PNU  802  has permission to use resources contained in other PNs regardless of locations of the resource in the PNF. 
         [0071]      FIG. 9  is a flow chart showing devices constituting a PNF. 
         [0072]    A PNF is a set of individual PNs, and each of the PNs operates in the same manner shown in  FIG. 6 . The PNF includes a PN# 1   900 , a PN# 2   901  and a PN# 3   902  that serve as individual PNs. A PNU  912  belonging to the PN# 1   900  is sequentially subject to initiation (operation  903 ) and registration (operation  904 ), which are performed for a resource sharing, and then performs a search for required resources (operation  905 ). In detail, a PNP# 1   913  of the PN# 1   900  searches for resources in a PD# 1   914  constituting the PN# 1   900 . If the resources requested by the PNU  912  are not found in the PN# 1   900 , the PNP# 1   913  transfers a resource search request to a PNP# 2   915  adjacent to the PNP# 1   913  (operation  906 ). If the PNP# 2   915  fails to find the resources requested by the PNU  912  in the PN# 2   901 , the PNP# 2   915  transfers a resource search request to a PNP# 3   917  adjacent to the PNP# 2   915  (operation  907 ). The PNP# 3   917  finds a PD# 3   918  containing the resources requested by the PNU  912 , and requests the PD# 3   918  to distribute the resources (operation  908 ). The PD# 3   918  distributes the resources to the PNU  912  (operation  910 ), and the PNU  912  receives and uses the requested resources (operation  911 ). 
         [0073]      FIG. 10  is a block diagram of a personal network (PN) system including a PD  1000 , a PNU  1010  and a PNP  1020 . 
         [0074]    The PD  1000  includes a resource retainer  1001  to retain resources, such as contents for example files or streaming data, and a PN agent  1002  for implementing a PN. The PN agent  1002  includes a controller  1003  and a data input/output unit  1004 . The controller  1003  performs a signaling for registration/signing off of the PD  1000  in/from the PN and a signaling for resource searching in the PN. The data input/output unit  1004  is responsible for input/output of the resources. The PNU  1010  is a user terminal which is directly operated by a user, and includes a resources retainer  1011  and a PN agent  1012  including a controller  1013  and a data input/output unit  1014 . The configuration of the PNU  1010  identical to that of the PD  1000  will be omitted in order to avoid redundancy. 
         [0075]    The PNP  1020  is a proxy server serving as a main part of the PN, and may be embodied as a device belonging to the PN or as an additional device similar to a home gateway. The PNP  1020  includes a controller  1021  and a data input/output unit  1022 . The controller  1021  performs a signaling with the controller  1003  of the PD  1000 , thereby managing the registration/signing off of the PD  1000  in/from the PN and the resource search in the PD. The data input/output unit  1022  manages input/output of resources. Resources may be transmitted/received between a PD and a PD, a PD and a PNU or a PNU and a PNU through respective input/output units of the PD, the PNU and the PNU. 
         [0076]    Meanwhile, the PNP  1020  further includes a format converter  1023 . The format converter  1023  is coupled to the data input/output unit  1022 . The format converter  1023  converts a format of contents of the PD  1000  and the PNU  1010  such that files of the PD  1000  and the PNU  1010  are provided in various formats. According to an exemplary embodiment, the format converter  1023  performs a codec conversion including the conversion of compression ratio and the alteration of codec. In addition, the format converter  1023  performs a conversion of content formats, for example, conversion of text format and conversion of voice format. If resources are indirectly transferred from the PD  1000  to the PNU  1010  through the PNP  1020 , the format converter  1023  converts a format of the resources such that the resource are available in the PNU  1010 . In addition, the PNP  1020  includes a database  1024 . The database  1024  includes a database of a user allowed to use the PN and a resource cache corresponding to information on resources stored in the PN. The resource cache stores a name of resources and information on location where resource are stored. 
         [0077]      FIG. 11  is a block diagram of a personal network federation (PNF) system. 
         [0078]    A PNF system further includes a PN-Coordinator  1100  in addition to the configuration shown in  FIG. 3 . The PN-Coordinator  1100  includes a controller  1110  and a PNP DB  1120 . The controller  1100  manages a registration of PNPs and enables a virtual routing such as an overlay networking between PNPs. The controller  1110  performs signaling to build a PNF by uniting PNs, which have resources required by the PNPs, with each other using a PNP list. 
         [0079]      FIG. 12  is a view showing a plurality of PNs constituting a PNF. Each of a PN# 1  to a PN# 6  includes a plurality of registered PDs. Such PNs are united to form a large-scaled virtual PN, that is, a PNF. A PN-Coordinator provides a PNP# 1  to a PNP# 6  with a list of predetermined PNPs forming a PNF. As shown in  FIG. 12 , the PN# 1 , the PN# 2  and the PN# 3  form a PNF  1200 . The PN# 1 , the PN# 2  and the PN# 4  form a PNF  1210 . The PN# 3 , the PN# 5  and the PN# 6  form a PNF  1220 . As shown in  FIG. 12 , a single PN may belong to different PNFs at the same time. 
         [0080]    It will be apparent to those of ordinary skill in the art that various modifications can be made to the exemplary embodiments of the invention described above. However, as long as modifications fall within the scope of the appended claims and their equivalents, they should not be misconstrued as a departure from the scope of the invention itself.