JPH10207791A - Hyper media system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain coherency between the original data of a public server and the cache data of a repeater system, and to efficiently attain data communication. SOLUTION: The informing means of a public server 1 transmits information related with updated original data in the public server 1 to a distributing device 4, and the distributing means of the distributing device 4 receives the information related with the updated data, and broadcasts it to a repeater system 2. Then, the updating means of the repeater system 2 receives the broadcast information related with the updated data, and updates cache data based on the information. Therefore, the updated original data in the public server 1 can be reflected on the cache data of the repeater system 2, and the coherency of the both data can be maintained. Also, cache to the plural repeater systems 2 can be attained while the data communicating amounts of a WAN 6 can be suppressed. Thus, hyper media data can be quickly provided to display devices 3 while the data amounts of a bi-directional communication network can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention caches data (hereinafter referred to as "hypermedia data") constituting hypermedia capable of linking with other data on a two-way communication network, and stores the cached data on the network. The present invention relates to a hypermedia system that suppresses data traffic.

[0002]

2. Description of the Related Art Conventionally, as a hypermedia system, a plurality of public servers holding hypermedia data capable of linking related data are connected to a two-way communication network, and furthermore, the public server holds the public servers. There are a plurality of display devices that perform processing requests for the processed hypermedia data, and for example, the World Wide Web (WWW) of the Internet is known as such a hypermedia system.

As data communication between a display device and a public server in such a hypermedia system, a request for processing such as retrieval is transmitted from the display device,
In response to the processing request, the public server executes the process using the hypermedia data, and returns the result to the display device in an interactive communication. And non-interactive communication that returns hypermedia data.

In the data communication described above, there is known a cache technology for reducing a response time to a processing request in a display device and reducing a data communication amount on a network. For example, JP-A-5-308366, or
Japanese Patent Application Laid-Open No. H7-168780 discloses that in a two-way communication network, data communicated in the past is stored in a cache buffer, and the next time the same data is requested,
An invention for responding to data in a cache buffer is disclosed. In addition, RFC (Request For Comments) 1945, h
ttp (hypertext trsnsport protocol) /1.0 standard 1.3
The section discloses a technique in which when performing data communication between a display device and a public server via a relay device (proxy server) in a two-way communication network, the relay device has a cache function.

[0005]

As described above, in the conventional hypermedia system, the display device stores the hypermedia data communicated with the public server as cache data in the relay device, and later displays the data. When there is a request for the same data from the device, data communication such as returning cache data of the relay device is performed. In this data communication, once the cached data is kept, if the hypermedia data (hereinafter, referred to as original data) in the public server is updated (added, changed, or deleted), the updated data is A situation occurs in which the original data differs from the cache data. Since hypermedia data is used, for example, to provide the latest information, it is generally updated frequently, and the above-described situation occurs frequently.

When the above situation occurs, the display device receives cache data different from the original data, and the characteristics of the hypermedia such that other data can be obtained by the link are destroyed. That is, the display device cannot not only obtain the original data, but also cannot appropriately obtain other data using the link of the original data.

As a method of preventing the above situation, there is a method of setting an expiration date for cache data and invalidating the cache data after the expiration date. However, it is difficult to set an expiration date with this method. . For example, if the expiration date is set relatively long, there is a high possibility that the original data will be updated before the expiration date, and a situation similar to the above will occur. On the other hand, if the expiration date is set relatively short, even if the original data has not been updated even after the expiration date, the cache data will be invalidated. Useless data communication such as caching is generated, and the effect of suppressing the data communication amount by the cache is diminished.

The present invention has been made in view of the above-described conventional circumstances, and provides a hypermedia system capable of maintaining consistency between original data and cache data and performing efficient data communication. It is intended to be.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for updating a public server to a relay device when original data is updated, in order to maintain consistency between the original data and cache data. And convey information about the data. Here, in order to transmit information about data updated from the public server to the plurality of relay devices only through the two-way communication network, the address of the destination relay device is grasped, and the same updated Information about the transmitted data has to be transmitted, the data communication volume of the two-way communication network increases, and the efficiency of data communication is low. Further, it is not easy to grasp the address of the relay device of the transmission destination.

Therefore, the present invention has been made by paying attention to a transmission form (broadcast) of information that does not specify a transmission destination, and broadcasts information relating to data updated in a public server and transmits it to a relay device. For example, broadcasting is realized by satellite broadcasting, terrestrial broadcasting, distribution of a recording medium (for example, CDROM) holding information, or the like.

[0011] In the hypermedia system according to the present invention, a public server holding data constituting the hypermedia and a plurality of relay devices holding data constituting the hypermedia provided to the display device are connected by a two-way communication network. In the connected hypermedia system, a distribution device is connected to the network, the public server is provided with a notification unit for transmitting information on the updated data to the distribution device, and the distribution device receives the information on the updated data. Distributing means for receiving and broadcasting to a plurality of relay devices is provided, and the relay device is provided with updating means for receiving information about the broadcasted update data and updating the held data based on the information. It is characterized by the following.

In the above hypermedia system,
The notifying means of the public server transmits information on the updated original data in the public server to the distribution device, and the distribution means of the distribution device receives the information on the updated data and broadcasts the information to the relay device. Then, the updating unit of the relay device receives the information on the broadcasted update data, and updates the cache data that constitutes the held hypermedia based on the received information.

Therefore, information on the updated data of the public server can be reflected on the data held in the relay device, and the consistency between the original data of the public server and the cache data of the relay device can be maintained. . Further, it is possible to cache the hypermedia data in a plurality of relay devices while suppressing the data communication amount of the two-way communication network, thereby quickly transmitting the hypermedia data to the display device and reducing the data communication amount of the two-way communication network. Can be provided with suppression.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A hypermedia system according to one embodiment of the present invention will be described with reference to FIG. This hypermedia system includes a public server 1 and a relay device 2
, A display device 3, a distribution device 4, and a communication satellite 5. The public server 1, the relay device 2, and the distribution device 4 are connected to a public line WAN (Wide A
network (rea Network) 6 and a LAN (Local Area Network) capable of bidirectional communication between the relay device 2 and the display device 3.
rk) 7, and a communication satellite 5 forms a path for broadcasting information from the distribution apparatus 4 to the plurality of relay apparatuses 2.

As shown in FIG. 2, the public server 1 includes a workstation (WS) 11, a hard disk device 12 for storing documents, and data using the WAN 6 between the WS 11 and the relay device 2 or the distribution device 4. A WAN interface 13 for mediating communication. Here, the document refers to a management unit for managing hypermedia data, and each document can form a link relationship with another document (not limited to a document in the same hard disk device 12).

The WS 11 distributes document management means for managing documents in the hard disk device 12, communication means for performing data communication with the relay device 2, and information on updated documents by using packets described later. And a notifying means for transmitting to the device 4. For example, as the WS 11, a workstation having a SPARC architecture (SPARC is a trademark of Sun Microsystems) is used.

As shown in FIG. 3, the relay device 2 includes a receiving antenna 21 and a satellite broadcast tuner / decoder device 22 for receiving information related to a document broadcast from the distribution device 4 via the communication satellite 5, and a WS 23.
And a hard disk device 24 for holding cache data relating to documents, a LAN interface 25 for mediating data communication between the WS 23 and the display device 1 using the LAN 7, and a WAN 6 between the WS 23 and the public server 3. A WAN interface 26 for mediating data communication.

The WS 23 includes a first communication unit for performing data communication with the display device 3, a second communication unit for performing data communication with the public server 1, a cache management unit for managing cache data, It has. Note that, for example, a workstation having a SPARC architecture is used as the WS 23.

As shown in FIG. 4, the display device 3 includes a display 31 and a speaker 32 as output means for outputting a document, a keyboard 33 and a mouse 34 as input means for inputting a document output request from a user. Personal computer (PC) 35 and PC
And a LAN interface 36 for mediating data communication between the relay device 2 and the relay device 2 using the LAN 7.

The PC 35 has communication means for transmitting the output request input by the input means to the relay device 2 via the LAN 7 and receiving a document corresponding to the output request from the relay device 2. Note that the above-described functional unit of the PC 35 is configured such that the processor executes an operating system (OS) and executes a program such as a WWW browser on the OS. PC can be used, an operating system manufactured by Microsoft can be used, and a WWW browser can be used by Netscape.

The above-mentioned public server 1, relay device 2, and display device 3 perform the following operations when a user requests the display device 3 to output a document. That is, when an output request for a document from a user is input by the input unit of the display device 3, the communication unit of the display device 3 transmits the output request to the relay device 2 via the LAN 7. Then, when the first communication unit receives the output request, the cache management unit detects whether or not the document corresponding to the output request is held in the hard disk device 24 as cache data.

If the corresponding document is held, the cache management means retrieves the document from the hard disk drive 24, and the first communication means transmits the retrieved document to the display device 3. Therefore, the display device 3 can be accessed without accessing the public server 1.
, The response time from the request on the display device 3 to the acquisition of the document can be shortened, and the amount of data communication on the network can be suppressed.

On the other hand, if the relevant document is not held, the relay device 2 receives the relevant document from the public server 1, converts the document into cache data, and transmits it to the display device 3. That is, the cache management unit transmits an output request to the public server 1 by the second communication unit, the communication unit of the public server 1 receives the output request, and the document management unit transmits a document corresponding to the received output request from the hard disk device. The document is retrieved and transmitted by the communication means of the public server 1 to the relay device 2, the document is received by the second communication means, and the document is stored in the hard disk device 24 as cache data by the cache management means, The first communication unit transmits the document to the display device 3. When the communication unit of the display device 3 receives the document from the relay device 2,
The output means outputs the received document.

When there is a subsequent output request for the same data based on the cache data stored in the hard disk device 24, the response time from the request on the display device 3 until the document is obtained is shortened. Thus, the amount of data communication on the network can be suppressed.

The above-described method of collecting cache data is conventionally known, and the cache data obtained by this method is hereinafter referred to as conventional cache data.

As shown in FIG. 5, the distribution device 4
And a hard disk device 42 for storing update information related to the document, and a W
It includes a WAN interface 43 for mediating data communication using the AN 6, a satellite encoder / modulator device 44 and a transmission antenna 45 for uploading update information on documents to the communication satellite 5.

The WS 41 includes a receiving unit that receives a packet including information on an updated document from the public server 1, a packet managing unit that manages a queue of packets in the hard disk device 42 according to a preset priority, and a satellite Distribution means for broadcasting a packet to the relay device 2 by the encoder / modulator device 44 and the transmission antenna 45. In addition,
The distributing means repeatedly broadcasts a plurality of times at a certain interval because the relay device 2 is not in the receiving system or the reception may fail.

Here, the packet that the distribution apparatus 4 receives from the notification means of the public server 1 will be described with reference to the drawings.
The packet includes an update packet including attribute value information relating to a changed or added document, a delete packet including attribute value information relating to a deleted or invalidated document, and a delete packet illustrated in FIG. Or, there is an entity packet including the document itself when added. Each packet has a configuration shown in FIG. 6B that includes a packet type field indicating the type of the packet and a data field.
The data field holds different data depending on the type of packet. That is, an update packet, or
In the case of a delete packet, a field block portion described later is held, and in the case of an entity packet, a document entity portion described later is held.

The above-mentioned packets are managed by the packet management means in a queue according to the priority shown in FIG. 6A, and are broadcast by the distribution means in the order of the queue.

Here, in this embodiment, the priority order is
The priority order is used to make the relay device 2 grasp the cache data stored in the relay device 2 different from the document of the public server 1 as quickly as possible. That is, when a document in the public server 1 is updated, the attribute information on the updated document is broadcasted preferentially, and in general, the entity of a document having a large data amount is broadcast after the attribute information. Is used. Also, in the attribute information about the updated document, from the attribute information about the deleted document, using a priority such that the attribute information about the added or changed document is preferentially broadcast,
This reliably prevents a situation where a document that should be actually obtained on the display device 3 cannot be obtained.

As described above, the packet broadcast by the distribution unit of the distribution device 4 is received by the relay device 2 and managed by the hard disk device 24 as cache data by the cache management unit. In addition,
The cache data thus obtained is hereinafter referred to as broadcast cache data. Here, the configuration of cache data managed by the cache management means will be described with reference to FIG. The conventional cache data and the broadcast cache data will be described together.

The cache data has a field block portion for storing the attributes of the document and a document entity for storing the entity of the document (a data set representing the contents of the document). The field block portion includes, as shown in FIG.
It has a pointer address field, a document ID field, a time stamp field, a hard expiration date field, a soft expiration date field, and a document entity pointer field.

The type field is a field indicating the type of cache data, and indicates, for example, one of conventional cache data and broadcast cache data. The pointer address field is a field for holding a character string given for uniquely identifying a document. As the character string, information indicating the name of the public server and the location where the public server is stored, for example, URL (Univer
sal Resource Locator) or URI (Uniform Resour)
ce Identifier) address.

The document ID field is a field for holding a character string (document ID) given for uniquely identifying the document entity of the document corresponding to the field block. The document ID of the conventional cache data is mechanically uniquely created when the cache management unit of the relay device 2 caches the document. The document ID of the broadcast-type cache data is mechanically and uniquely created by the notifying means of the public server 1 holding the original document.

Here, the character string given for uniquely identifying the document entity is the same character string even if the documents are stored in different locations and the document entity is the same. That is, by preparing such a character string, when a plurality of documents have the same document entity, only one document entity needs to be managed, and the storage efficiency of the hard disk device 24 is improved. be able to.

The time stamp field is a field for holding the time when the original document was last updated. The hard expiration date field is a field that holds the expiration date (hard expiration date) that can guarantee that the cache data is synchronized with the original document when the document is cached. This field is invalid in conventional cache data.

The hardware expiration date includes, for example, the next update time of the document ascertained by the document administrator, and is set by the notification means of the public server 1. Therefore, before the hard expiration date, it means that the cache data matches the original document. Therefore, a request to discard the cache data from the display device 3 and transfer the latest document from the public server 1 has been given. Even in this case, the cache management unit does not discard the cache data, and returns the cache data to the display device 3 as the latest document. Note that, when information on the document is transmitted to the relay device 2 by broadcasting, the cache data becomes invalid before the hardware expiration date.

The soft expiration date field is a field for holding the time (soft expiration date) of the expiration date for retaining cache data. The software expiration date is set for the conventional cache data and the broadcast type cache data by the cache management means, and when the software expiration time is reached, the cache data is discarded by the cache management means. In the broadcast cache data, the software expiration date is set to a time after the hardware expiration date.

The document entity pointer field is:
This field stores an internal address indicating the storage location of the document entity corresponding to the field block. If the document entity to be referenced is not stored in the hard disk drive 24, for example, upda
If the te packet has been received, but the entity packet corresponding to the document represented by the update packet has not been received by broadcast, the pointer is a null pointer. Note that the time stored in the above-mentioned field is, for example, universal time (UTC)
There is a time in the form of the number of seconds that have elapsed since midnight on January 1, 1970.

As shown in FIG. 7 (b), the document entity has a document ID field, a link counter field, a last link time field, a size field, and a document entity field. The document ID field is a field for holding a document ID of a document entity stored in the document entity part.

The link counter field is a field for holding the number of field block parts referring to the document substantial part. The number stored in this field is increased or decreased when the cache management means creates or deletes a field block portion referring to the document entity portion. The last link time field is a field that holds the last time the link counter has increased or decreased. Note that, even when the link counter becomes "0", the cache management unit does not immediately delete the document entity part but deletes the document entity part after a certain time has elapsed from the last link time.

The size field is a field representing the size of the document entity held in the document entity field in bytes. The document entity field is a field that holds byte string data representing the document entity.

Next, the operation when the document of the public server 1 is updated in the above-described hypermedia system will be described with reference to the drawings. When the document managed by the document management unit is updated in the public server 1, the notification unit transmits information on the updated document to the distribution device 4 using a packet. When the communication unit of the distribution device 4 receives the transmitted packet, the packet is formed in a queue according to the priority set by the packet management unit, and the distribution device transmits the packet in the order of the queue to the satellite encoder / modulator. Broadcast by the device 44 and the transmitting antenna 45.

The broadcasted packet is received by the receiving antenna 21 of the relay unit 2 and the satellite broadcast tuner / decoder device 22, and the cache management unit determines the type of the received packet. The following processing is performed according to the type. Do. That is, if the received packet is an update packet, as shown in FIG. 8, the cache management unit determines whether the packet satisfies the cache condition (step S1). Here, as the cache condition, for example, a condition relating to a document to be cached, such as caching only a document on a public server in Japan, is set. It is a condition. Note that the same applies to the cache conditions used in the following description.

If the cache condition is not satisfied, the process is terminated. On the other hand, if the cache condition is satisfied, the document is to be cached. It is detected whether or not the cache data having the same pointer address as the address exists in the hard disk drive 24 (step S2). If so, the time stamp of the update packet is further compared with the time stamp of the cache data. (Step S
3).

If the time stamps match, it means that the updated document matches the cache data, and the process ends as it is. On the other hand, if the cache data does not exist or the cache data exists but the time stamp does not match, it means that the updated document is not reflected in the cache data. Register it in the hard disk drive 24 (step S4).

If the received packet is a delete packet, as shown in FIG. 9, the cache management means determines whether or not the packet satisfies the cache condition (step S5). If not, the document corresponding to the packet is not held as cache data, so the process ends.If the cache condition is satisfied, the document is cached. Therefore, it is detected whether or not cache data having the same pointer address as the pointer address held in the field block portion of the delete packet exists in the hard disk drive 24 (step S6). If there is no cache data, the process is terminated as it is, while if there is cache data, the corresponding cache data is deleted from the hard disk drive 24 (step S7).

If the received packet is an entity packet, as shown in FIG. 10, the cache management means determines whether or not the packet satisfies the cache condition (step S8). If not, the process ends.If the cache condition is satisfied, the document is cached.
It is determined whether or not a document entity having the same document ID exists in the hard disk drive 24 (step S9). If the document exists, the document entity is already stored in the hard disk drive 24, so the processing is terminated as it is.
The document entity in the packet is registered in the hard disk drive 24 (step S10).

As described above, the document updated in the public server 1 can be appropriately reflected in the cache data of the relay device 2. In reflecting the updated data, it is not necessary to know the relay device 2 to which the updated document is to be reflected.
This can be efficiently reflected on the plurality of relay devices 2.
In addition, the cache data can reduce the communication amount of the two-way communication network and can quickly provide the display device 3 with the document data.

Next, the operation of the hypermedia system when the broadcast cache data is held in the relay device 2 will be described in detail with reference to FIG.

When the user inputs a pointer address representing a desired document by the input means of the display device 3, the communication means of the display device 3 transmits the pointer address to the relay device 2 and the first communication of the relay device 2 is performed. The means receives the pointer address (step S11), and the cache management means detects whether or not the cache data holding the same pointer address as the pointer address exists in the hard disk drive 24 (step S12).

If there is no cache data holding the same pointer address, the following cache miss processing is performed. That is, the second communication means transmits the pointer address to the public server 1, the communication means of the public server 1 receives the pointer address, and the document management means stores the field block portion relating to the document corresponding to the received pointer address on the hard disk. The information is acquired based on the document of the device 12, the field block portion is transmitted by the communication means of the public server 1 to the relay device 2, and the field block portion is received by the second communication means (step S13).

Then, the document ID of the document corresponding to the field block received by the cache management means is set (step S14). Further, the second communication means receives the document entity of the document corresponding to the pointer address by the same processing as in step S13 described above (step S15). Next, the first communication means transmits the document entity in the document entity part to the display device 3 (step S16). As a result, the communication means of the display device 3 receives the document entity, and the output means outputs the document.

The document management means detects whether or not the document corresponding to the field block portion and the document substantive portion satisfies the cache condition (step S17). The field block part and the document substance part are stored in the hard disk drive 24 (steps S18, S19).

On the other hand, if there is cache data holding the same pointer address, the cache management means detects whether the hardware expiration date of the field block portion of the cache data has expired or is invalid ( In step S20), if it is expired or invalid, the second communication means receives the field block portion of the document corresponding to the pointer address by the same processing as in step S13 (step S21). Further, the cache management unit compares the time stamp of the field block portion of the cache data with the time stamp of the received field block portion (Step S22).

If the two time stamps do not match, the cache management means discards the cache data held in the hard disk (step S23) and performs the above-described processing (steps S13 to S19). On the other hand, if the hard expiration date has not expired, or if it has expired or is invalid but has the same time stamp, it means that the updated document and the cache data match. Then, the cache management unit extracts the document entity from the hard disk drive 24 using the document entity pointer of the field block unit, and the first communication unit transmits the document entity of the document entity to the display device 3 (steps S24 and S25). .

Incidentally, in the case of the broadcast type cache data, a situation may occur in which the document substantive part is not stored in the hard disk drive 24.
In this case, the above processing (steps S15 to S1)
Perform 9). Therefore, the display device 3 is the public server 1
Can be reliably obtained.

In the above-described embodiment, when the broadcast is performed in accordance with the priority, the information on the update data is stored as a queue according to the priority, and the information is broadcast in accordance with the queue. Information may be stored, and the stored information may be extracted according to the priority and broadcast.

In the above embodiment, each of the display device, the public server, the relay device, and the distribution device is constituted by a different processing terminal (WS or PC). It can also be configured by a processing terminal. In other words, one processing terminal may have functional units of arbitrary plural devices.

Each of the functional units described above constituted by the processor executing a program (prestored in ROM, RAM, etc.) may be constituted as an independent hardware circuit. In addition, the present invention allows the above-mentioned program to be grasped as a storage medium such as a floppy disk or a CD-ROM, and causes the processor to execute the program according to the present invention by executing the program by inputting the program from the storage medium. Can also.

[0061]

As described above, in the hypermedia system according to the present invention, the information on the data constituting the updated hypermedia is cached in the relay device by broadcasting. While keeping the data consistent with the original data on the public server,
It is possible to efficiently cache a plurality of relay devices. In addition, by using a broadcast having a relatively low cost, the amount of data communication using a bidirectional communication network having a relatively high cost can be suppressed, and the cost can be reduced. Further, in the hypermedia system according to the present invention, information on data constituting the updated hypermedia is broadcast according to a preset priority, so that important information for cache data in the relay device is stored. It can be reflected quickly.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a hypermedia system according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a public server according to an embodiment of the present invention.

FIG. 3 is a configuration diagram of a relay device according to an embodiment of the present invention.

FIG. 4 is a configuration diagram of a display device according to an embodiment of the present invention.

FIG. 5 is a configuration diagram of a distribution device according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating a structure of a packet including information on updated data.

FIG. 7 is a diagram illustrating a data structure of cache data.

FIG. 8 is a first flowchart illustrating a cache management operation by a cache management unit of the relay device according to one embodiment of the present invention.

FIG. 9 is a second flowchart illustrating a cache management operation performed by the cache management unit of the relay device according to the embodiment of the present invention.

FIG. 10 is a third diagram illustrating a cache management operation by the cache management unit of the relay device according to the embodiment of the present invention;
It is a flowchart.

FIG. 11 is a flowchart illustrating an operation of the hypermedia system according to one embodiment of the present invention.

[Explanation of symbols]

1. Public server, 2. Relay device, 3. Display device, 4. Distribution device, 5. Communication satellite,
6 ... WAN, 7 ... LAN.

Claims (2)

[Claims] 1. A hypermedia system in which a public server holding data constituting hypermedia and a plurality of relay devices holding data constituting hypermedia provided to a display device are connected by a two-way communication network. A distribution device connected to the network, the public server is provided with a notification unit for transmitting information on the updated data to the distribution device, and the distribution device receives the information on the updated data and receives a plurality of relay devices. Hypermedia, comprising: a distribution unit that broadcasts data to the relay device; and a relay device that receives information about the updated data that has been broadcast, and updates the held data based on the information. system. 2. The hypermedia system according to claim 1, wherein the distribution device has a storage unit for storing a plurality of notified update data, and distributes the data stored in the storage unit in accordance with a preset priority. And a distribution control means for causing the means to broadcast.