Electrical computers and digital processing systems: multicomput – Distributed data processing – Client/server
Reexamination Certificate
1999-06-29
2002-11-12
Lim, Krisna (Department: 2153)
Electrical computers and digital processing systems: multicomput
Distributed data processing
Client/server
C709S217000, C709S218000, C709S219000, C709S232000
Reexamination Certificate
active
06480883
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a client/server type system wherein an information providing server provides information upon request from an information display client, and more particularly to a real-time information transmission system for realizing novel and advantageous information transmission from an information providing server to an information display client.
In these years, the WWW (World Wide Web) has permeated through societies, and various information is provided via the WWW. The WWW is a distributed-type information-provision/information-display system using the Internet, and it comprises servers (information providing servers) and clients. As is well known, a worldwide information network using hypertexts including images and sounds has been constructed by the WWW and utilized by many people.
In general, the server provides information to the client in units of a document called “page”. The page is an electronic file described in a format called HTML (Hypertext Markup Language). The client is normally realized with use of a software called “browser” for information display (information browsing), and the browser accesses the server to acquire and display pages including images and sounds.
In the general use of the WWW, an address (called URL) of a page to be displayed is designated in the browser, and the browser issues a request to the server. The server returns the page corresponding to the address to the browser. It should be noted here that the server performs nothing unless it receives a request from the browser. This means that even if pages stored in the server have been updated, the browser is unable to immediately know the change.
For example, while the browser is displaying pages such as news and weather reports, which are updated in real time, the browser is not informed of the fact that the pages have been updated on the server side. That is, the content of the updated page is not reflected on the display screen of the browser side.
The user on the browser side can immediately know the update of the page stored in the server, if the browser accesses the server periodically. In this case, however, the user needs to periodically re-access the server, for example, by depressing a reload button generally provided in the browser, and this means that a very time-consuming operational load is put on the user.
There is known a mechanism called “smart-pull mechanism” as an example of the mechanism for automatically updating the display of the page on the browser side in accordance with the update of the page on the server side. In the smart-pull mechanism, the browserside operation by the user of positively depressing the reload button is automated. The smart-pull mechanism provides the user with such a feeling that the page updated on the server side is automatically sent to the browser, like TV broadcasting.
There is a mechanism called “push mechanism” as another example of the mechanism for automatically updating the display of the page on the browser side. The push mechanism is provided with means for extending an HTML file provided by the information providing server (WWW server), thereby describing in the HTML file various information relating to the display update of the page. The browser, which has received the extended HTML file, refers to information described in the HTML file, which relates to, e.g. the next update time. If the next update time has arrived, the browser issues a request for provision of the updated page to the server. According to the push mechanism, a useless access to the server can be eliminated and such an effect that the page is updated as if in real time can be obtained with the browser-side processing alone.
As examples of such browsers having the automatic function of periodically accessing the server and being capable of reducing the operational load on the user, “Point Cast” (produced by Point Cast corporation) and “Castanet Tuner” (produced by Marimba corporation) have been provided. These browsers are provided with such devices as enable the user to designate the time interval of automatic update or the browser to receive only different data on the updated page.
In the above-described smart-pull mechanism and push mechanism, it is the browser, and not the server, that updates the display of the page. As mentioned above, even when the page stored in the server has been updated, unless the browser issues a request, the server performs nothing. This characteristic of the client/server system causes some problems described below.
In the smart-pull mechanism, the browser automatically accesses the server on a periodical basis in order to check whether the page has been updated. Although no special attribute is needed in the HTML file constituting the page, the periodical access is repeated unconditionally even if the server-side information is, in fact, not updated, and useless accesses will increase.
On the other hand, the push mechanism is based on the special file (extended HTML file) in which information indicating the next update time is described beforehand as page attribute. Thus, no useless access to the server is performed to check whether the information has been updated on the server side, if it is assumed that the page is actually updated on the server side according to the information on the update time.
However, the push mechanism is effective only in the case where the next update time or timing can be specified in advance. Specifically, in the push mechanism, if it is assumed that the page is updated asynchronously and at a non-specified timing, the update time information cannot be prepared. That is, the client side is unable to know when the automatic update is to be made.
There is a common problem with the smart-pull mechanism and the push mechanism. That is, when the update interval of the page to be provided is very short, e.g. one second, the efficiency of communication processing is very low. The reason is as follows. In general, when communication is started between the server and client, some communication negotiations need to be performed before data is transmitted. In the above example, negotiations have to be performed every one second. In this case, the ratio of the negotiations to the transmission/reception of page text will increase, and the communication efficiency from the standpoint of communication cost, etc. decreases.
It appears that this problem will be solved if the server can voluntarily and directly send updated information to the client, independently from the request by the client. In view of the framework of the current WWW, however, this ideal is not practical. The reason is as follows.
In the current WWW, there is a case where a plurality of relay servers intervene between the server and client. Some relay servers are provided with mechanisms called “firewall” for transferring information only in one direction. The firewall is generally used, in particular, in companies, in order to prevent outside intruder from entering the systems within the companies (e.g. Intranet).
Where such relay servers intervene, the object with which the client directly communicates is the relay server closest to the client, and the object with which the server directly communicates is the relay server closest to the server. Accordingly, the direct client of the server is this relay server, and the server cannot specify the client used by the user on the network.
As a result, the server cannot directly send an update notification to the browser. Moreover, since the intervening relay server receives accesses from many non-specified clients or servers, there is a problem with reliability or stability. It is not ensured that the update notification from the server is quickly sent to the client with safety and exactness.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above circumstances, and an object of the invention is to provide a real-time information transmission system for realizing real-time information transmission f
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
Lim Krisna
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