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Updating local copy of shared data in a collaborative system

  • US 5,220,657 A
  • Filed: 04/15/1991
  • Issued: 06/15/1993
  • Est. Priority Date: 12/02/1987
  • Status: Expired due to Term
First Claim
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1. A method for operating a collaborative system that includes a plurality of workstations each having a respective display, a respective user input device, and a respective local memory the collaborative system further including storage means for storing shared data;

  • each of the workstations being connected for accessing the shared data stored by the storage means to retrieve the shared data for storage in the respective local memory and for presentation on the respective display;

    the method comprising steps of;

    receiving from the respective user input device of a first one of the workstations a signal requesting an operation affecting the shared data; and

    in response to the signal requesting the operation, performing the following acts substeps of;

    locking the shared data stored by the storage means to prevent other operations affecting the shared data;

    determining whether an up-to-date copy of the affected shared data is stored in the respective local memory of the first workstation;

    if an up-to-date copy of the affected shared data is not stored in the respective local memory of the first workstation, storing an up-to-date copy of the affected shared data in the respective local memory of the first workstation;

    performing the requested operation by making a change in the up-to-date copy of the affected shared data stored in the respective local memory of the first workstation;

    updating the shared data stored by the storage means to include the change made by performing the requested operation; and

    unlocking the shared data stored by the storage means after the shared data stored by the storage means is updated.

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