JP2004062497A - Data communication system and method for correcting data generation time - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data communication system capable of preventing a situation from occurring that the order of individual data at the moment of data generation becomes different from the actual generation order of the individual data in each terminal when data communication is performed. <P>SOLUTION: The data communication system is provided with a plurality of terminals 10 and the data are communicated among the terminals 10. Each of the terminals 10 is provided with: a time imparting part 13 for imparting a data generation time to the data when the data are generated; a control part 15 for transmitting its own system time at the time of data transmission in addition to the data and the data generation time when transmitting the data to the other terminal; and a time correction part 16 for taking, when receiving the data from the other terminal, a difference between the system time of the other terminal sent together with the data and its own system time at the time of data reception and correcting the data generation time imparted to the data on the basis of the difference. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a data communication system that corrects a data generation time given to data when performing data communication between terminals, and a method of correcting the data generation time.
[0002]
[Prior art]
Currently, data communication systems capable of performing data communication between terminals are widely used. For example, in many companies, a network is constructed by connecting a plurality of computers via a LAN or the like. Then, by communicating data between the computers, the data can be managed centrally. In addition, a portable terminal such as a PDA and a computer can be connected by a temporary communication link, and data can be exchanged between them.
[0003]
Generally, computers and portable terminals are provided with a clock circuit that measures the current time and the date (system time). The system time is used, for example, when data is generated, to add a data generation time (time stamp) to the data. When data communication is performed between the terminals, the time stamp is transmitted together with the data.
[0004]
[Problems to be solved by the invention]
By the way, it is rare that the system time of each terminal is the same, and there are many cases where the system time is shifted from each other. For this reason, when data generated in another terminal is transmitted to the terminal, when the terminal manages the transmitted data and the data generated in the terminal together, the order of each data by the time stamp is The order of occurrence of each data may be different.
[0005]
The present invention has been made based on the above circumstances, and when performing data communication, a situation occurs in which the order of each data according to the data generation time differs from the actual generation order of each data at each terminal. It is an object of the present invention to provide a data communication system and a data generation time correction method capable of preventing the occurrence of the error.
[0006]
[Means for Solving the Problems]
The present invention for achieving the above object has a plurality of terminals, a data communication system capable of performing data communication between each terminal, wherein each terminal, when data occurs, Time providing means for providing a data generation time to the generated data; and when transmitting the data to another terminal, in addition to the data and the data generation time provided to the data, the own time at the time of the data transmission. Transmission control means for transmitting the system time, and when receiving data from another terminal, take the difference between the system time of the other terminal sent together with the data and its own system time at the time of receiving the data, And a time correcting means for correcting the data generation time given to the data based on the difference.
[0007]
Further, the present invention for achieving the above object is a data generation time correction method for correcting the data generation time given to data when performing data communication between two terminals, When transmitting data from a terminal to another terminal, the one terminal transmits its own system time at the time of the data transmission, in addition to the data and the data generation time added to the data, The terminal takes a difference between the system time of the one terminal sent together with the data and its own system time at the time of receiving the data, and corrects the data generation time given to the data based on the difference. It is characterized by the following.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a data communication system according to an embodiment of the present invention, and FIG. 2 is a schematic functional block diagram of each terminal in the data communication system.
[0009]
The data communication system of the present embodiment includes a plurality of terminals 10 as shown in FIG. Such a data communication system may be, for example, a system including a client and a server. In this case, the client and the server are connected by a LAN or the like, and a network is constructed. Thus, data communication can be performed between the clients or between the client and the server. The data communication system may be, for example, a system including at least one computer and a plurality of mobile terminals. In this case, when the two mobile terminals or the computer and the mobile terminal are connected by a temporary communication link, data communication can be performed between the mobile terminals or between the computer and the mobile terminal. FIG. 1 illustrates a case where each terminal 10 is a computer.
[0010]
In the present embodiment, a case will be considered in which data communication is performed between the terminals 10 about once a day. A specific example is a case where a salesman carries a mobile terminal and goes out, and then when he returns to the company, data generated on that day is transmitted from the mobile terminal to the company computer. .
[0011]
As shown in FIG. 2, each terminal 10 includes a storage unit 11, a clock circuit 12, a time giving unit 13, a communication unit 14, a control unit 15, and a time correction unit 16.
[0012]
The storage unit 11 stores data generated in the terminal 10. Here, “occurred data” includes both newly created data and updated data.
[0013]
The clock circuit 12 manages the current time and the date, that is, the system time. Ordinary computers and portable terminals are equipped with such a timing circuit 12. The user can adjust the system time measured by the clock circuit 12. The time assigning unit 13 assigns a system time measured by the clock circuit 12 to the data when the data is generated, as a data generation time (time stamp). The time stamp is one of the attribute information of the data, and indicates a creation time or an update time of the data.
[0014]
The communication unit 14 is for performing data communication with another terminal 10. The control unit 15 controls the entire terminal 10. Specifically, when transmitting data to another terminal 10, the control unit 15 transmits its own system time at the time of transmitting the data, in addition to the data and the time stamp attached to the data.
[0015]
In general, it is rare that the system times of the terminals 10 are coincident with each other, and there are many cases where the system times are shifted from each other. Even if the system times of all the terminals 10 are set to the same time, there is a difference in how the system time of each terminal 10 advances due to the individual difference of the clock circuit 12, and as the time elapses, the system of each terminal 10 Times are shifted from each other. In addition, for example, in a mobile terminal or the like, it is often the case that the system time is incorrectly set for one hour.
[0016]
As described above, since the system time of each terminal 10 is different, when data generated at another terminal 10 is transmitted to the terminal 10, the data transmitted at the terminal 10 and the data generated at the terminal 10 are generated. When managing data together, the order of each data according to the time stamp may be different from the actual generation order of each data. In the present embodiment, the time correction unit 16 is provided to prevent the order of each data based on the time stamp from being different from the actual generation order of each data. When receiving data from another terminal 10, the time correction unit 16 calculates a difference between the system time of the other terminal 10 sent together with the data and its own system time at the time of receiving the data, and calculates the difference. The time stamp given to the data is corrected based on the time stamp. That is, by adding or subtracting the difference to or from the time stamp of the data transmitted from another terminal 10, the time stamp of the transmitted data is rewritten to a time based on its own system time.
[0017]
The time correction unit 16 that corrects such a time stamp can be easily realized by incorporating a program for causing the control unit 15 to execute the correction processing into the terminal 10.
[0018]
Next, an operation for correcting a time stamp of data in the data communication system of the present embodiment will be described. FIG. 3 is a diagram for explaining an operation of correcting a data time stamp in the data communication system.
[0019]
Assume that there are two terminals A and B as shown in FIG. 3A, and data generated at each of the terminals A and B is exchanged. In each of the terminals A and B, when data is generated, the time giving unit 13 gives a time stamp to the data. That is, in the terminals A and B, a time stamp is added to the generated data using their own system times. The example of FIG. 3A shows a case where three data are generated at the terminal A and two data are generated at the terminal B. The data generated at the terminal A is stored in the storage unit 11 of the terminal A together with the time stamp, while the data generated at the terminal B is stored in the storage unit 11 of the terminal B together with the time stamp. Thus, data is stored independently in each of the terminals A and B.
[0020]
Next, as shown in FIG. 3 (b), the terminal A and the terminal B perform data communication and exchange data generated at each. At this time, in the terminal A, the control unit 15 transmits the system time of the terminal A at the time of data transmission in addition to the three data (including the time stamp) stored in the storage unit 11. Similarly, in the terminal B, the control unit 15 transmits the system time of the terminal B at the time of data transmission, in addition to the two data (including the time stamp) stored in the storage unit 11. Here, at the time of data communication, the terminal A and the terminal B are synchronized, and the timing at which the terminal A acquires the system time at the time of data transmission and the timing at which the terminal B acquires the system time at the time of data transmission Is consistent with In addition, the system time at the time of data transmission obtained by each of the terminals A and B in this manner is also the system time at the time of data reception.
[0021]
When the terminal A receives data from the terminal B, the time correction unit 16 of the terminal A determines the system time of the terminal B at the time of data transmission and the system time of the terminal (terminal A) at the time of data reception. Take the difference with Then, based on the difference, the time stamp given to each received data is corrected. This correction processing will be specifically described. If the system time of the terminal A at the time of data reception is ahead of the system time of the terminal B at the time of data transmission by the time T, the time correction unit 16 of the terminal A adds the time T to the time stamp of each received data. to add. Each time after the addition becomes a new time stamp of the corresponding data. Then, the control unit 15 of the terminal A stores the received data together with the new time stamp in the storage unit 11. On the other hand, if the system time of the terminal A at the time of data reception is later than the system time of the terminal B at the time of data transmission by the time T, the time correction unit 16 of the terminal A determines the time from the time stamp of each received data. Subtract T. Each time after the subtraction becomes a new time stamp of the corresponding data. Then, the control unit 15 of the terminal A stores the received data together with the new time stamp in the storage unit 11. As a result, the terminal A can rewrite the time stamp of the data generated at the terminal B based on its own system time.
[0022]
Even when the terminal B receives the data from the terminal A, the terminal B performs the time stamp correction process in the same manner as described above. That is, the time correction unit 16 of the terminal B obtains the difference between the system time of the terminal A at the time of transmitting the data transmitted together with the received data and the like and the system time of the terminal (the terminal B) at the time of receiving the data. , The time stamp added to each received data is corrected. Specifically, if the system time of the terminal B at the time of data reception is ahead of the system time of the terminal A at the time of data transmission by the time T, the time correction unit 16 of the terminal B determines the time of each received data. The time T is added to the stamp. Each time after the addition becomes a new time stamp of the corresponding data. Then, the control unit 15 of the terminal B stores the received data together with the new time stamp in the storage unit 11. On the other hand, when the system time of the terminal B at the time of data reception is later than the system time of the terminal A at the time of data transmission by the time T, the time correction unit 16 of the terminal B determines the time from the time stamp of each received data. Subtract T. Each time after the subtraction becomes a new time stamp of the corresponding data. Then, the control unit 15 of the terminal B stores the received data together with the new time stamp in the storage unit 11. As a result, the terminal B can rewrite the time stamp of the data generated in the terminal A with reference to its own system time.
[0023]
By the way, in the present embodiment, in data communication, in principle, a process of making the system time of one terminal coincide with the system time of the other terminal is not performed. This is because it cannot be unconditionally determined which terminal has the correct system time. However, for example, in a system in which a main terminal and a sub terminal are determined in advance, such as a system including a client and a server or a system including a computer and a mobile terminal, the sub terminal is a main terminal. When performing data communication with the device and recognizing that the system time of the terminal itself is significantly different from the system time of the main terminal, a warning is displayed to the effect that the system time of the terminal is adjusted to the system time of the main terminal It may be displayed on the means or an alarm indicating that effect may be issued. Alternatively, the sub terminal may adjust its own system time to match the system time of the main terminal based on the system time of the main terminal at the time of transmitting data sent from the main terminal. Good. This is because in a system in which a main terminal and a sub terminal are determined, it is desirable to give priority to the system time of the main terminal. In addition, for example, in a mobile terminal or the like, it is often the case that the system time is incorrectly set for one hour. In such a case, a setting error of the system time can be recognized or corrected easily. The above-described process of displaying a warning or issuing a warning, or the process of matching the system time can be easily realized by incorporating a program for causing the control unit to execute the process in a terminal.
[0024]
In the data communication system of the present embodiment, each terminal, when transmitting data to another terminal, in addition to the data and its time stamp, a control unit that transmits its own system time at the time of data transmission, When data is received from the terminal, the difference between the system time of the other terminal sent together with the data and the own system time at the time of receiving the data is taken, and the time stamp given to the data based on the difference is taken. And a time correction unit for correcting As a result, each terminal can rewrite the time stamp of data generated at another terminal based on its own system time. Can be prevented from being different from the actual order in which the data is generated.
[0025]
In addition, since the processing for correcting the time stamp can be realized by software, in the data communication system of the present embodiment, it is not necessary to add new hardware, and the manufacturing cost of each terminal increases considerably. There is also the advantage that there is nothing.
[0026]
Note that the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the gist.
[0027]
In the above embodiment, the case where the frequency of exchanging data between the terminals is about once a day has been described, but the frequency of data exchange may be lower. For example, data may be exchanged between terminals approximately once a month. However, when the frequency of data exchange is low as described above, it is necessary to consider that the degree of deviation of the system time per day may be different for each terminal when correcting the time stamp of data. . That is, when data is transmitted from another terminal, the time correction unit of each terminal corrects the time stamp of the data based on the system time difference at the time of data transmission and reception this time, as described above. Correction is performed taking into account that the degree of deviation of the system time per day varies from terminal to terminal.
[0028]
This latter correction is specifically performed as follows. That is, the time correction unit first calculates the difference between the system time difference at the time of the current data transmission and reception and the system time difference at the time of the previous data transmission and reception. This difference (difference change amount) indicates how much the difference between the system times of the two terminals has changed between the time of the previous data transmission and reception and the current data transmission and reception. Further, based on the current data transmission / reception time, the number of days before the data has occurred in the past is calculated. Next, the time correction unit obtains the average difference change amount per day, and multiplies the obtained average difference change amount by the number of days of the data calculated retroactively based on the current data transmission / reception time. . The time obtained by this multiplication is the time stamp correction amount for the data.
[0029]
【The invention's effect】
As described above, in the data communication system according to the present invention, when transmitting data to another terminal, each terminal transmits its own system time at the time of data transmission in addition to the data and the data generation time. Transmission control means, which, when receiving data from another terminal, takes a difference between the system time of the other terminal sent together with the data and its own system time at the time of data reception, and takes the difference based on the difference. Time correction means for correcting the data generation time given to the data. As a result, each terminal can rewrite the occurrence time of data generated in another terminal based on its own system time, so that there is a difference in the system time of each terminal. It is possible to prevent a situation where the order is different from the actual generation order of each data.
[0030]
In addition, in the method of correcting the data generation time according to the present invention, each terminal can rewrite the generation time of data generated in another terminal with reference to its own system time, as described above. It is possible to prevent the occurrence of a situation in which the order of each data according to the data generation time differs from the actual generation order of each data due to the difference in the system time.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a data communication system according to an embodiment of the present invention.
FIG. 2 is a schematic functional block diagram of each terminal in the data communication system.
FIG. 3 is a diagram for explaining an operation of correcting a time stamp of data in the data communication system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Terminal 11 Storage unit 12 Clock circuit 13 Time giving unit 14 Communication unit 15 Control unit 16 Time correction unit

Claims (2)

A data communication system having a plurality of terminals and capable of performing data communication between the terminals,
Each of the terminals,
A time giving means for giving a data occurrence time to the generated data when data is generated;
When transmitting data to another terminal, in addition to the data and the data generation time given to the data, transmission control means for transmitting its own system time at the time of the data transmission,
When data is received from another terminal, the difference between the system time of the other terminal sent together with the data and the own system time at the time of receiving the data is calculated, and the difference is added to the data based on the difference. Time correction means for correcting the data occurrence time,
A data communication system comprising: When performing data communication between two terminals, a data generation time correction method for correcting the data generation time given to the data,
When transmitting data from one terminal to another terminal, the one terminal transmits its own system time at the time of the data transmission, in addition to the data and the data generation time given to the data, The other terminal calculates a difference between the system time of the one terminal transmitted together with the data and its own system time at the time of receiving the data, and calculates a data generation time given to the data based on the difference. A method of correcting a data generation time, wherein the correction is performed.

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