Electrical computers and digital processing systems: multicomput – Computer conferencing
Reexamination Certificate
1999-03-11
2001-04-24
Lim, Krisna (Department: 2153)
Electrical computers and digital processing systems: multicomput
Computer conferencing
C709S205000, C709S213000, C709S216000
Reexamination Certificate
active
06223212
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to a computer method and system for sharing an application program and, more specifically, to a method and system for sharing an application program with multiple computer systems.
BACKGROUND OF THE INVENTION
The modern workplace is increasingly reliant on the use of networks. A network is a group of computer systems and associated devices that are connected by communications facilities. A network enables the transfer of electronic information between computer systems. Typically, each of the computer systems has local application programs which can be invoked at that computer system. Also, each local application program displays output at that computer system.
Some computer systems allow a user at a host computer system to share an application program (i.e., a shared application program) with one other user at one other computer system (i.e., a shadow computer system). However, it would be usefull for a user to be able to share an application program invoked at a host computer system with other users at multiple shadow computer systems. An application program is shared by executing the application program on the host computer system, by displaying the output of the application program (i.e., output data) on the display of the shadow computer system, and by receiving input for the application program from the host computer system and the shadow computer system.
For example, an editor who is working with an editorial staff to publish a newspaper can benefit from sharing an application program that generates a word processing document. In particular, the contents of the newspaper can be stored as a word processing document, and the editor can edit the format of each page of the word processing document at the editor's computer system and allow the members of the editorial staff to view the word processing document at their computer systems. The editor can share the word processing program with each staff member. The members of the editorial staff can view the changes made by the editor and provide input to the word processing program to modify the document based on the editor's revisions. Immediately, the editor can review these modifications to the document.
Additionally, when a user at a host computer system is sharing an application program with one other user at a shadow computer system, it is useful for the user at the shadow computer system to view an accurate representation of the output of the application program displayed at the host computer system. To enable the shadow computer system sharing the application program to display an accurate representation of this output data, each computer system exchanges capabilities which indicate how input data to an application program is to be processed and how output data from an application program is to be displayed. The capabilities include, for example, pixel depth, desktop size, order formats, font data, and palette data. Upon receiving the capabilities of the other computer system, a computer system identifies sharing capabilities that are capabilities that both computer systems support.
When a user at a host computer system starts sharing an application program with another user at a shadow computer system, the users initially exchange capabilities. Then, each computer system identifies sharing capabilities which represent the capabilities that both computer systems support. Both computer systems process and display output data using the sharing capabilities so that the output data displayed at the shadow computer system accurately represents the output data displayed at the host computer system.
When users at multiple computer systems are sharing an application program, it would be useful for each user to see an accurate representation of the output of the application program at the host computer system. It would also be usefill for a user at a new computer system to join in sharing the application program. Moreover, it would be useful for a user at a computer system which is already sharing an application program to stop sharing the application program, while users at other computer systems continue to share the application program. As a user joins in sharing or stops sharing the application program, it would be useful for each user to continue to see an accurate representation of the output of the application program at the host computer system. Because the sharing capabilities can change as a user joins in sharing or stops sharing the application program, when users at multiple computer systems sharing an application program exchange capabilities only initially, as when only two computer systems are sharing an application program, the output data displayed at the host computer system cannot be accurately represented at each other computer. It would be useful to be able to identify the appropriate sharing capabilities to be used at each computer system sharing the application program when users join in or stop sharing the application program to ensure that the output data displayed at the shadow computer system accurately represents output data displayed at the host computer system.
SUMMARY OF THE INVENTION
The present invention provides several techniques for coordinating the sharing of an application with multiple computer systems. The computer systems negotiate capabilities in a application sharing conference. Each computer system in the conference has capabilities with capability values. To negotiate capabilities, each computer system advertises its capability values to each other computer system. Each computer system uses a predefined algorithm to determine sharing capabilities. Each computer system independently sets the negotiated capability values to the same set of values. In particular, when a capability is designated as being negotiated according to a one capability rule, each computer system sets the capability value for the capability to the advertised capability value of a specified computer system. When a capability is designated as being negotiated according to a max capability rule, then each computer system determines candidate capability values from the advertised capability values. Each computer system then sets the capability value for the capability to the maximum of all the determined candidate capability values. When a capability is designated as being negotiated according to a min capability rule, each computer system determines candidate capability values from the advertised capability values. Each computer system then sets the capability value for the capability to the minimum of all the determined candidate capability values.
In another aspect, the present invention provides a method for coordinating the exchange of data of computer systems that are sharing an application. Each computer system maintains a local share identifier. When a computer system is inactive in the sharing of the application, the computer system sets its local share identifier to invalid. When a computer system is to become active in the sharing of the application, the computer system generates a share identifier. The computer system then sets the local share identifier to the generated share identifier and sends the generated share identifier along with a demand to become active. When a computer system receives a demand to become active, if the local share identifier is invalid, the computer system sets the local share identifier to the share identifier received with the demand to become active. Otherwise, the computer system sets the local share identifier to the greater of the local share identifier and the share identifier received with the demand to become active. When a computer system is to confirm a demand to become active, the computer system sends the local share identifier along with a confirmation to become active. When a computer system receives a confirmation to become active, if the local share identifier is invalid, the computer system sets the local share identifier to the share identifier received with the confirmation to become active. O
Batty John P.
Downes Anthony M.
Hughes Kenneth P.
MacFarquhar Roderick F.
Mairs Christopher J.
Leydig , Voit & Mayer, Ltd.
Lim Krisna
Microsoft Corporation
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