Data processing: database and file management or data structures – Database design – Data structure types
Utility Patent
1998-06-22
2001-01-02
Black, Thomas G. (Department: 2771)
Data processing: database and file management or data structures
Database design
Data structure types
C707S793000, C709S200000
Utility Patent
active
06169988
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a data sharing system for sharing a database provided on a server among a plurality of terminal equipment connected to the server via a network, and more particularly, to a data sharing system for efficiently transferring data between the server and the terminal equipment.
2. Description of the Related Art
In this kind of data sharing system, necessary data may be downloaded from a server through a network line and stored into a database on a relevant terminal equipment, for the purpose of making use of the data stored in a database of a server. When only one terminal equipment is connected to a server, if reusing the data that has been once downloaded, the data stored in the database of the relevant terminal equipment can be available. However, in a data sharing system having a plurality of terminal equipment connected to a server, the data stored in the database of the server may have been updated by a different terminal equipment, and therefore, the latest data must be downloaded through access to the server every time a user makes use of the data.
This way of downloading the latest data from the database of the server every time data is required is very inefficient. Especially, it is a serious problem when the capacity of a network line is small.
A conventional technique to improve this defect is disclosed in, for example, Japanese Patent Publication Laid-Open (Kokai) No. Heisei 6-131305, “Radio Electronic Mail System”. In the technique disclosed in the same publication, when the data stored in the database of a server is updated, the update history of the database is held. When a terminal equipment has access to the database, this update history is downloaded and the updating of the data is notified to the terminal equipment, and subsequently only the data that has been updated later than the last access is downloaded to be combined with the data stored in the database of the terminal equipment, thereby decreasing the communication amount.
The conventional system disclosed in the above publication, however, is on the assumption that a single user deals with a single database, and therefore, a user cannot necessarily refer to the latest data when a plurality of users share a plurality of databases. This is why, when a plurality of users share a plurality of databases, the data a given user wants to refer to has been already updated by another user, or the updated content by another user may not be reflected in the database of the server at the point when the given user gains access to the database of the server. In such a case, the given user cannot obtain the latest data that has been updated.
Further, when a terminal equipment is connected to a server via a network that may establish a connection at a necessary time, such as a dial-up connection by use of a telephone line, a connection between the both units must be established every time a user wants to gain the latest data from the server, which has been inefficient. Especially, when establishing a connection by use of an unstable line such as a public line by radio, there is a case in which a lot of connection trials, in spite of being in the impossible state of connection, would occupy the line, which has been very inefficient.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a data sharing system capable of always referring to the latest data even in the case of sharing a plurality of databases among a plurality of users, for the purpose of efficient data transfer, by controlling the transfer destination of the data stored in a database of a server.
Another object of the present invention is to provide a data sharing system capable of decreasing useless connection trials, for the purpose of efficient data transfer, by controlling the communication history in each terminal equipment and the moving schedule of each terminal equipment in a server and predicting whether a connection to a given terminal equipment can be established.
According to one aspect of the invention, a data sharing system comprising a server, which is provided with a database with various data stored therein, capable of transferring the data between another calculating machine and itself and a terminal equipment having an application program capable of receiving the data held by the server through a network and at least referring to the data, for transferring the data between the server and the terminal equipment, wherein
the server comprises
a connection party holding means for holding access information indicating relationship between a data name of the transferred data and a calculating machine name of a transfer destination when transferring data, and
the terminal equipment comprises
a data acquiring means for supplying a deciding request of a connection party calculating machine for acquiring corresponding data, depending on
the necessity, based on the reference request, when a data reference request has been issued from the application program and submitting the corresponding data obtained from the server or the given connection party calculating machine to the application program, and
a connection party deciding means for deciding a connection party from calculating machines holding the data corresponding to the reference request, with reference to the access information held by the connection party holding means of the server, according to the connection party deciding request supplied from the data acquiring means,
the data acquiring means, when the reference request is issued,
judging whether the data name of the data specified by the reference request exists in the connection party holding means, with reference to the access information held by the connection party holding means of the server,
acquiring the corresponding data by issuing the transfer request of the corresponding data to the database of the server when there is not the data name in the connection party holding means, and
supplying a connection party deciding request for deciding a calculating machine of a connection party and further issuing a data transfer request to the
connection party decided by the connection party deciding means so as to obtain the corresponding data when there is the data name.
In the preferred construction, when the reference request is issued, the data acquiring means of the terminal equipment checks whether the corresponding data is held in the own terminal equipment and when it is held, submits the corresponding data being held to the application program without accessing the server or the given connection party calculating machine.
In the preferred construction, in the terminal equipment, the application program includes a function of updating data in addition to data reference, and the data acquiring means supplies the update request to the database of the server when an update request of data is issued from the application program, while
in the server, the database updates corresponding data in reply to the update request, and the connection party holding means records the relationship between a data name of updated data in the database and a calculating machine name of the terminal equipment having issued the above update request.
In the preferred construction, in the terminal equipment, the application program includes a function of updating data in addition to data reference, and the data acquiring means supplies the update request to the database of the server when an update request of data is issued from the application program, while
in the server, the database updates corresponding data in reply to the update request, and the connection party holding means records the relationship between a data name of updated data in the database and a calculating machine name of the terminal equipment having issued the above update request, and when data of the database system is updated and a terminal equipment other than the terminal equipment having issued the update request refers to the updated data, the terminal equipment having is
Black Thomas G.
Coby Frantz
Foley & Lardner
NEC Corporation
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