CA2446283A1 - Method and apparatus for maintaining consistency of a shared space across multiple endpoints in a peer-to-peer collaborative computer system - Google Patents
Method and apparatus for maintaining consistency of a shared space across multiple endpoints in a peer-to-peer collaborative computer system Download PDFInfo
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- CA2446283A1 CA2446283A1 CA002446283A CA2446283A CA2446283A1 CA 2446283 A1 CA2446283 A1 CA 2446283A1 CA 002446283 A CA002446283 A CA 002446283A CA 2446283 A CA2446283 A CA 2446283A CA 2446283 A1 CA2446283 A1 CA 2446283A1
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F15/00—Digital computers in general; Data processing equipment in general
- G06F15/16—Combinations of two or more digital computers each having at least an arithmetic unit, a program unit and a register, e.g. for a simultaneous processing of several programs
- G06F15/163—Interprocessor communication
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L63/00—Network architectures or network communication protocols for network security
- H04L63/04—Network architectures or network communication protocols for network security for providing a confidential data exchange among entities communicating through data packet networks
- H04L63/0428—Network architectures or network communication protocols for network security for providing a confidential data exchange among entities communicating through data packet networks wherein the data content is protected, e.g. by encrypting or encapsulating the payload
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L63/00—Network architectures or network communication protocols for network security
- H04L63/12—Applying verification of the received information
- H04L63/123—Applying verification of the received information received data contents, e.g. message integrity
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S707/00—Data processing: database and file management or data structures
- Y10S707/99931—Database or file accessing
- Y10S707/99938—Concurrency, e.g. lock management in shared database
Abstract
[190, In a peer-to-peer collaboration system, deltas containing data change commands are organized in a persistent data structure called a delta log. The delta log is organized into blocks, which are the largest division in the delta log. In turn, blocks contain groups, groups contain chains and chains contain deltas. Delta blocks are used to implement priority deltas that are used to limit the collection of data change commands that must be transferred. Within a block the deltas are organized by groups, each of which is a set of deltas organized into chains. The delta group in used to determine which deltas to purge. The chains are ordered by increasing creator ID of the endpoint that created the chain. Organizing the delta log in this fashion allows the log to be "walked" to detect convergence problems. To achieve causality-preservation, each delta has a list of dependencies representing other deltas that must be executed before the current delta can be executed. The dynamics manager uses the ability to do (execute) and undo commands to perform roll back and roll forward operations on deltas in order to achieve convergence.
Claims (78)
1. Apparatus for maintaining consistency of a shared space across multiple endpoints in a collaborative computer system wherein each endpoint has a local data copy and endpoints transmit data change commands contained in deltas to each other in order to update the local data copies, the apparatus comprising:
a persistent delta log data structure located in each endpoint that stores deltas and their contents;
a mechanism in each endpoint that inserts each delta generated by the each endpoint and received from other endpoints into the delta log so that each delta received from an endpoint is kept in a chain in order of generation and reception; and a mechanism in each endpoint that executes the data change commands in a delta, the mechanism using the contents of the delta log to selectively undo and redo data change commands in order to achieve convergence of the data change commands at all endpoints.
a persistent delta log data structure located in each endpoint that stores deltas and their contents;
a mechanism in each endpoint that inserts each delta generated by the each endpoint and received from other endpoints into the delta log so that each delta received from an endpoint is kept in a chain in order of generation and reception; and a mechanism in each endpoint that executes the data change commands in a delta, the mechanism using the contents of the delta log to selectively undo and redo data change commands in order to achieve convergence of the data change commands at all endpoints.
2. The apparatus of claim 1 wherein a delta generated by the each endpoint and received from other endpoints is inserted into a delta log at a point determined by the endpoint that generated that delta and a sequence number.
3. The apparatus of claim 1 wherein each chain in a delta log is comprised of deltas received from an endpoint ordered by the sequence number.
4. The apparatus of claim 1 wherein each chain in a delta log has a predetermined maximum length.
5. The apparatus of claim 1 wherein the chains in the delta log are arranged in groups wherein, within each group, chains are arranged in order of increasing creator ID wherein the creator ID is the combination of an endpoint ID for an endpoint and a random number generated each time that endpoint opens the shared space.
6. The apparatus of claim 1 further comprising a mechanism for generating endpoint pulses that are transmitted between the endpoints in the shared space wherein each endpoint pulse is generated by an endpoint and comprises information identifying a delta group that that endpoint is willing to delete.
7. The apparatus of claim 6 further comprising means in each endpoint that receives endpoint pulses generated by other endpoints and deletes deltas in groups selected by comparing the information in the endpoint pulses in order to determine delta groups that all endpoints are willing to delete.
8. The apparatus of claim 1 wherein the mechanism in each endpoint that executes the data change commands in a delta comprises a mechanism that uses the chains in a delta log to sequentially examine deltas in order to undo data change commands in selected deltas.
9. The apparatus of claim 8 wherein the mechanism in each endpoint that executes the data change commands in a delta comprises a mechanism that uses the chains in a delta log to sequentially examine deltas in order to redo data change commands that had been previously undone.
10. The apparatus of claim 1 wherein each delta has a list of dependencies representing other deltas that must be executed before the each delta can be executed.
11. The apparatus of claim 10 wherein the mechanism in each endpoint that executes the data change commands in a delta comprises means for using undo information contained in a delta in order to undo data change commands contained in that delta.
12. The apparatus of claim 11 further comprising a data change engine that inserts undo information into a delta at the same time that data change commands in the delta are executed.
13. The apparatus of claim 10 wherein the mechanism in each endpoint that inserts each delta generated by the each endpoint and received from other endpoints into the delta log inserts the delta chains into blocks based on a priority assigned to each delta so that each block contains one delta with highest priority, all deltas on which the highest priority delta depends are located in blocks created before the each block, all deltas that are independent of the highest priority delta are in the each block and all deltas that depend on the highest priority delta are in the each block and blocks created after the each block.
14. The apparatus of claim 10 further comprising a mechanism for creating an asynchronous delta wherein no other deltas are dependent on the asynchronous delta.
15. The apparatus of claim 10 further comprising a mechanism in an endpoint for fetching from other endpoints deltas in a list of dependencies, which deltas are not in the delta log of that endpoint.
16. The apparatus of claim 15 wherein the mechanism for fetching deltas sends a fetch request to another endpoint including a fetch request sequence number and wherein the other endpoint comprises a fetch response mechanism that includes a fetch response sequence number and wherein the fetch response mechanism returns requested deltas to the mechanism for fetching deltas when the fetch request sequence number is equal to the fetch response sequence number.
17. The apparatus of claim 16 wherein the fetch response mechanism sends an update message to the mechanism for fetching when the fetch request sequence number is not equal to the fetch response sequence number.
18. The apparatus of claim 17 wherein the mechanism for fetching is responsive to the update message for incrementing the fetch request sequence number.
19. The apparatus of claim 10 further comprising a mechanism for creating an identity disseminated delta that is sent to a subset of endpoints in the shared space and which is inserted into a delta log at a point determined by the endpoint that generated that delta and a sub-sequence number.
20. The apparatus of claim 1 further comprising a mechanism in each endpoint for storing persistent data representing a state of all endpoints in the shared space including an active state end a mechanism for sending deltas only to endpoints with an active state.
21. The apparatus of claim 20 wherein the mechanism in each endpoint that executes the data change commands in a delta is responsive to a state of the endpoint that generated the delta for selectively executing the data change commands in the delta.
22. The apparatus of claim 20 wherein each endpoint has a current state and each endpoint comprises a mechanism that changes the endpoint current state to another state in response to a predetermined event.
23. A method for maintaining consistency of a shared space across multiple endpoints in a collaborative computer system wherein each endpoint has a local data copy and endpoints transmit data change commands contained in deltas to each other in order to update the local data copies, the method comprising:
(a) storing deltas and their contents in a persistent delta log data structure located in each endpoint;
(b) inserting each delta generated by the each endpoint and received from other endpoints into the delta log so that each delta received from an endpoint is kept in a chain in order of generation and reception; and (c) executing the data change commands in a delta, the mechanism using the contents of the delta log to selectively undo and redo data change commands in order to achieve convergence of the data change commands at all endpoints.
(a) storing deltas and their contents in a persistent delta log data structure located in each endpoint;
(b) inserting each delta generated by the each endpoint and received from other endpoints into the delta log so that each delta received from an endpoint is kept in a chain in order of generation and reception; and (c) executing the data change commands in a delta, the mechanism using the contents of the delta log to selectively undo and redo data change commands in order to achieve convergence of the data change commands at all endpoints.
24. The method of claim 23 wherein step (b) comprises inserting a delta generated by the each endpoint and received from other endpoints into a delta log at a point determined by the endpoint that generated that delta and a sequence number.
25. The method of claim 23 wherein each chain in a delta log is comprised of deltas received from an endpoint ordered by the sequence number.
26. The method of claim 23 wherein each chain in a delta log has a predetermined maximum length.
27. The method of claim 23 wherein step (b) comprises arranging the chains in the delta log in groups wherein, within each group, chains are arranged in order of increasing creator ID wherein the creator ID is the combination of an endpoint ID
for an endpoint and a random number generated each time that endpoint opens the shared space.
for an endpoint and a random number generated each time that endpoint opens the shared space.
28. The method of claim 23 further comprising:
(d) generating endpoint pulses that are transmitted between the endpoints in the shared space wherein each endpoint pulse is generated by an endpoint and comprises information identifying a delta group that that endpoint is willing to delete.
(d) generating endpoint pulses that are transmitted between the endpoints in the shared space wherein each endpoint pulse is generated by an endpoint and comprises information identifying a delta group that that endpoint is willing to delete.
29 The method of claim 28 further comprising:
(e) receiving endpoint pulses generated by other endpoints and deleting deltas in groups selected by comparing the information in the endpoint pulses in order to determine delta groups that all endpoints are willing to delete.
(e) receiving endpoint pulses generated by other endpoints and deleting deltas in groups selected by comparing the information in the endpoint pulses in order to determine delta groups that all endpoints are willing to delete.
30. The method of claim 23 wherein step (c) comprises using the chains in a delta log to sequentially examine deltas in order to undo data change commands in selected deltas.
31. The method of claim 30 wherein step (c) comprises using the chains in a delta log to sequentially examine deltas in order to redo data change commands that had been previously undone.
32. The method of claim 23 wherein each delta has a list of dependencies representing other deltas that must be executed before the each delta can be executed.
33. The method of claim 32 wherein step (c) comprises using undo information contained in a delta in order to undo data change commands contained in that delta.
34. The method of claim 33 further comprising:
(d) inserting undo information into a delta at the same time that data change commands are executed.
(d) inserting undo information into a delta at the same time that data change commands are executed.
35. The method of claim 32 wherein step (b) comprises inserting the delta chains into blocks based on a priority assigned to each delta so that each block contains one delta with highest priority, all deltas on which the highest priority delta depends are located in blocks created before the each block, all deltas that are independent of the highest-priority delta are in the each block and all deltas that depend on the highest priority delta are in the each block and blocks created after the each block.
36. The method of claim 32 further comprising:
(d) creating an asynchronous delta wherein no other deltas are dependent on the asynchronous delta.
(d) creating an asynchronous delta wherein no other deltas are dependent on the asynchronous delta.
37. The method of claim 32 further comprising:
(d) fetching to a first endpoint from other endpoints deltas in a list of dependencies, which deltas are not in the delta log of the first endpoint.
(d) fetching to a first endpoint from other endpoints deltas in a list of dependencies, which deltas are not in the delta log of the first endpoint.
38. The method of claim 37 wherein step (d) comprises sending a fetch request from the first endpoint to another endpoint including a fetch request sequence number and wherein the other endpoint comprises a fetch response mechanism that includes a fetch response sequence number and wherein step (d) further comprises returning requested deltas from the another endpoint to the first endpoint when the fetch request sequence number is equal to the fetch response sequence number.
39. The method of claim 38 wherein step (d) further comprises sending an update message to first endpoint when the fetch request sequence number is not equal to the fetch response sequence number.
40. The method of claim 39 wherein step (d) further comprises incrementing the fetch request sequence number in response to the update message.
41. The method of claim 32 further comprising creating an identity disseminated delta that is sent to a subset of endpoints in the shared space and inserting the identity disseminated delta into the delta log at a point determined by the endpoint that generated that delta and a sub-sequence number.
42. The method of claim 23 further comprising:
(d) storing persistent data in each endpoint representing a state of all endpoints in the shared space including an active state; and (e) sending deltas only to endpoints with an active state.
(d) storing persistent data in each endpoint representing a state of all endpoints in the shared space including an active state; and (e) sending deltas only to endpoints with an active state.
43. The method of claim 42 wherein step (c) comprises selectively executing the data change commands in the delta in response to a state of the endpoint that generated the delta.
44. The method of claim 42 wherein each endpoint has a current state and the method further comprises:
(f) changing the endpoint current state to another state in response to a predetermined event.
(f) changing the endpoint current state to another state in response to a predetermined event.
45. A computer program product for maintaining consistency of a shared space across multiple endpoints in a collaborative computer system wherein each endpoint has a local data copy and endpoints transmit data change commands contained in deltas to each other in order to update the local data copies, the computer program product comprising a computer usable medium having computer readable program code thereon, including:
program code for storing deltas and their contents in a persistent delta log data structure located in each endpoint;
program code for inserting each delta generated by the each endpoint and received from other endpoints into the delta log so that each delta received from an endpoint is kept in a chain in order of generation and reception; and program code for executing the data change commands in a delta, the mechanism using the contents of the delta log to selectively undo and redo data change commands in order to achieve convergence of the data change commands at all endpoints.
program code for storing deltas and their contents in a persistent delta log data structure located in each endpoint;
program code for inserting each delta generated by the each endpoint and received from other endpoints into the delta log so that each delta received from an endpoint is kept in a chain in order of generation and reception; and program code for executing the data change commands in a delta, the mechanism using the contents of the delta log to selectively undo and redo data change commands in order to achieve convergence of the data change commands at all endpoints.
46. The computer program product of claim 45 wherein the program code for inserting each delta into the delta log comprises program code for inserting a delta generated by the each endpoint and received from other endpoints into a delta log at a point determined by the endpoint that generated that delta and a sequence number.
47. The computer program product of claim 45 wherein each chain in a delta log is comprised of deltas received from an endpoint ordered by the sequence number.
48. The computer program product of claim 45 wherein each chain in a delta log has a predetermined maximum length.
49. The computer program product of claim 45 wherein the program code for inserting each delta into the delta log comprises program code for arranging the chains in the delta log in groups wherein, within each group, chains are arranged in order of increasing creator ID wherein the creator ID is the combination of an endpoint ID for an endpoint and a random number generated each time that endpoint opens the shared space.
50. Apparatus for maintaining consistency of a shared space across multiple endpoints in a collaborative computer system wherein each endpoint has a local data copy and endpoints transmit data change commands contained in deltas to each other in order to update the local data copies, the apparatus comprising:
a persistent delta log data structure located in each endpoint that stores deltas and their contents;
means in each endpoint for inserting each delta generated by the each endpoint and received from other endpoints into the delta log so that each delta received from an endpoint is kept in a chain in order of generation and reception;
and means in each endpoint for executing the data change commands in a delta, the executing. means using the contents of the delta tog to selectively undo and redo data change commands in order to achieve convergence of the data change commands at all endpoints.
a persistent delta log data structure located in each endpoint that stores deltas and their contents;
means in each endpoint for inserting each delta generated by the each endpoint and received from other endpoints into the delta log so that each delta received from an endpoint is kept in a chain in order of generation and reception;
and means in each endpoint for executing the data change commands in a delta, the executing. means using the contents of the delta tog to selectively undo and redo data change commands in order to achieve convergence of the data change commands at all endpoints.
51. The apparatus of claim 50 wherein the inserting means is responsive to a delta generated by the each endpoint and received from other endpoints for inserting the delta into a delta log at a point determined by the endpoint that generated that delta and a sequence number.
52. The apparatus of claim 50 wherein each chain in a delta log is comprised of deltas received from an endpoint ordered by the sequence number.
53. The apparatus of claim 55 wherein each chain in a delta log has a predetermined maximum length.
54. The apparatus of claim 50 wherein the inserting means comprises means for arranging chains in the delta log into groups wherein, within each group, chains are arranged in order of increasing creator ID wherein the creator ID is the combination of an endpoint ID for an endpoint and a random number generated each time that endpoint opens the shared space.
55. Apparatus for maintaining consistency of a shared space across multiple endpoints in a collaborative computer system wherein each endpoint has a local data copy and endpoints transmit data change commands to each other in order to update the local data copies, the apparatus comprising:
a first tool in one endpoint that is responsive to user actions at the endpoint for creating a first delta container to transmit data change commands to other endpoints and for adding data change commands to the first delta container;
a second tool in the one endpoint that is called by the first tool to add data change commands to the first delta container; and means in the second tool for creating a second delta container, adding the second delta container to the first delta container and adding data change commands to the second delta container.
a first tool in one endpoint that is responsive to user actions at the endpoint for creating a first delta container to transmit data change commands to other endpoints and for adding data change commands to the first delta container;
a second tool in the one endpoint that is called by the first tool to add data change commands to the first delta container; and means in the second tool for creating a second delta container, adding the second delta container to the first delta container and adding data change commands to the second delta container.
56. The apparatus of claim 55 wherein at least one of the data change commands includes undo information for reversing the data change performed by the command.
57. The apparatus of claim 55 further comprising a data change engine for executing the data change commands in the first delta container and the data change commands in the second delta container and a dynamics manager for adding the data change commands in the second delta container and undo information corresponding to the data change commands in the second delta container to the beginning of the first delta container.
58. The apparatus of claim 57 wherein the data change engine executes data change commands added to the first delta container before the second delta container was added to the first delta container after the data change commands in the second delta container are executed and added.
59. The apparatus of claim 58 wherein the data change engine comprises means responsive to the occurrence of an error during the execution of the data change commands in the first delta container for aborting the execution of the data change commands in the second delta container.
60. A method for maintaining consistency of a shared space across multiple endpoints in a collaborative computer system wherein each endpoint has a local data copy and endpoints transmit data change commands to each other in order to update the local data copies, the method comprising:
(a) using a first tool to create a first delta container in response to user actions at one endpoint to transmit data change commands to other endpoints;
(b) using the first tool to add data change commands to the first delta container;
(c) calling a second too! in the one endpoint with the first tool to add data change commands to the first delta container;
(d) creating a second delta container with the second tool; and (e) using the second tool to add the second delta container to the first delta container and to add data change commands to the second delta container.
(a) using a first tool to create a first delta container in response to user actions at one endpoint to transmit data change commands to other endpoints;
(b) using the first tool to add data change commands to the first delta container;
(c) calling a second too! in the one endpoint with the first tool to add data change commands to the first delta container;
(d) creating a second delta container with the second tool; and (e) using the second tool to add the second delta container to the first delta container and to add data change commands to the second delta container.
61. The method of claim 60 wherein at least one of the data change commands includes undo information for reversing the data change performed by the command.
62. The method of claim 60 further comprising:
(f) executing the data change commands in the second delta container and the data change commands in the first delta container; and (g) after executing the data change commands in the second delta container, adding the data change commands in the second delta container and undo information corresponding to the data change commands in the second delta container to the beginning of the first delta container.
(f) executing the data change commands in the second delta container and the data change commands in the first delta container; and (g) after executing the data change commands in the second delta container, adding the data change commands in the second delta container and undo information corresponding to the data change commands in the second delta container to the beginning of the first delta container.
63. The method of claim 62 wherein step (f) comprises executing the data change commands added to the first delta container before the second delta container was added after step (g) is performed.
64. The method of claim 58 further comprising:
(h) aborting the execution of the data change commands in the second delta container upon the occurrence of an error during the execution of the data change commands in the first delta container.
(h) aborting the execution of the data change commands in the second delta container upon the occurrence of an error during the execution of the data change commands in the first delta container.
65. Apparatus for maintaining consistency of a shared space across multiple endpoints in a collaborative computer system wherein each endpoint has a local data copy and endpoints transmit data change commands contained in delta containers to each other in order to update the local data copies, the apparatus comprising:
a data change engine in one endpoint for executing the data change commands in a first delta container, for generating undo information in order to reverse the effects of the data change commands and for storing the undo information in the first data change container;
means in the data change engine and responsive to the execution of a selected data change command for creating a second delta container in the one endpoint and for adding data change commands to the second delta container.
a data change engine in one endpoint for executing the data change commands in a first delta container, for generating undo information in order to reverse the effects of the data change commands and for storing the undo information in the first data change container;
means in the data change engine and responsive to the execution of a selected data change command for creating a second delta container in the one endpoint and for adding data change commands to the second delta container.
66. The apparatus of claim 65 further comprising means for executing the commands in the second delta container and for generating undo information for reversing the effects of the commands in the second delta container and means operable upon execution for storing the commands in the second delta container and undo information generated for those commands in the undo information of the first delta container.
67. The apparatus of claim 66 further comprising means for using the undo information in the first delta container to reverse the effect of the commands contained in the first delta container wherein the means for using the undo information reverses commands originally stored in the second delta container before the selected command that caused the second delta container to be created is reversed.
68. A method for maintaining consistency of a shared space across multiple endpoints in a collaborative computer system wherein each endpoint has a local data copy and endpoints transmit data change commands contained in delta containers to each other in order to update the local data copies, the method comprising:
(a) executing the data change commands in a first delta container, generating undo information in order to reverse the effects of the data change commands and storing the undo information in the first data change container;
(b) responsive to the execution of a selected data change command, creating a second delta container in the one endpoint; and (c) adding data change commands to the second delta container.
(a) executing the data change commands in a first delta container, generating undo information in order to reverse the effects of the data change commands and storing the undo information in the first data change container;
(b) responsive to the execution of a selected data change command, creating a second delta container in the one endpoint; and (c) adding data change commands to the second delta container.
69. The method of claim 68 further comprising:
(d) executing the commands in the second delta container and generating undo information for reversing the effects of the commands in the second delta container; and (e) storing the executed commands from the second delta container and undo information generated for those commands in the undo information of the first delta container.
(d) executing the commands in the second delta container and generating undo information for reversing the effects of the commands in the second delta container; and (e) storing the executed commands from the second delta container and undo information generated for those commands in the undo information of the first delta container.
70. The method of claim 69 further comprising:
(f) using the undo information in the first delta container to reverse the effect of the commands contained in the first delta container; and (g) during the performance of step (f) reversing commands originally stored in the second delta container before the selected command that caused the second delta container to be created is reversed.
(f) using the undo information in the first delta container to reverse the effect of the commands contained in the first delta container; and (g) during the performance of step (f) reversing commands originally stored in the second delta container before the selected command that caused the second delta container to be created is reversed.
71. Apparatus for maintaining consistency of a shared space across multiple endpoints in a collaborative computer system wherein each endpoint has a local data copy and endpoints transmit data change commands contained in deltas to each other in order to update the local data copies, the apparatus comprising:
a conflict region in each delta that identifies other deltas with which the execution of the each delta conflicts;
a persistent delta log data structure located in each endpoint that stores deltas and their contents;
a mechanism in each endpoint that inserts each delta generated by the each endpoint and received from other endpoints into the delta log in a consistent order across all endpoints based on a group number and sequence number in that delta; and a data engine that walks backward over the delta log starting from the last delta entered and proceeding towards the first delta entered and compares the conflict regions of each executed delta with the conflict regions of other deltas entered into the log and reverses the effect of each executed delta that conflicts with another delta entered into the log.
a conflict region in each delta that identifies other deltas with which the execution of the each delta conflicts;
a persistent delta log data structure located in each endpoint that stores deltas and their contents;
a mechanism in each endpoint that inserts each delta generated by the each endpoint and received from other endpoints into the delta log in a consistent order across all endpoints based on a group number and sequence number in that delta; and a data engine that walks backward over the delta log starting from the last delta entered and proceeding towards the first delta entered and compares the conflict regions of each executed delta with the conflict regions of other deltas entered into the log and reverses the effect of each executed delta that conflicts with another delta entered into the log.
72. The apparatus of claim 71 wherein the data engine comprises means for reversing the effect of each executed delta that has a conflict by iterating in reverse order over the data change commands in the delta and using undo information in the delta for each data change command to reverse the effect of the command.
73. The apparatus of claim 72 wherein, after reversing the effect of each delta that conflicts with another delta, the data change engine walks backward over the delta log starting from the last delta entered and proceeding towards the first delta entered and re-executes the data change commands in each delta that was reversed.
74. The apparatus of claim 73 wherein the conflict region of each delta is set when the delta is created.
75. A method for maintaining consistency of a shared space across multiple endpoints in a collaborative computer system wherein each endpoint has a local data copy and endpoints transmit data change commands contained in deltas to each other in order to update the local data copies, the method comprising:
(a) creating a conflict region in each delta that identifies other deltas with which the execution of the each delta conflicts;
(b) storing deltas and their contents in a persistent delta tog data structure located in each endpoint;
(c) inserting each delta generated by the each endpoint and received from other endpoints into the delta fog in a consistent order across all endpoints based on a group number and a sequence number in that delta; and (d) walking backward over the delta log starting from the last delta entered and proceeding towards the first delta entered, comparing the conflict regions of each executed delta with the conflict regions of other deltas entered into the log and reversing the effect of each executed delta that conflicts with another delta entered into the log.
(a) creating a conflict region in each delta that identifies other deltas with which the execution of the each delta conflicts;
(b) storing deltas and their contents in a persistent delta tog data structure located in each endpoint;
(c) inserting each delta generated by the each endpoint and received from other endpoints into the delta fog in a consistent order across all endpoints based on a group number and a sequence number in that delta; and (d) walking backward over the delta log starting from the last delta entered and proceeding towards the first delta entered, comparing the conflict regions of each executed delta with the conflict regions of other deltas entered into the log and reversing the effect of each executed delta that conflicts with another delta entered into the log.
76. The method of claim 75 wherein step (d) comprises reversing the effect of each executed delta that has a conflict by iterating in reverse order over the data change commands in the delta and using undo information in the delta for each data change command to reverse the effect of the command.
77. The method of claim 75 further comprising:
(e) after reversing the effect of each delta that conflicts with another delta, walking backward aver the delta log starting from the last delta entered and proceeding towards the first delta entered and re-executing the data change commands in each delta that was reversed.
(e) after reversing the effect of each delta that conflicts with another delta, walking backward aver the delta log starting from the last delta entered and proceeding towards the first delta entered and re-executing the data change commands in each delta that was reversed.
78. The method of claim 77 wherein step (a) comprises creating the conflict region of each delta when the delta is created.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US10/279,785 | 2002-10-24 | ||
| US10/279,785 US7340502B2 (en) | 2002-10-24 | 2002-10-24 | Method and apparatus for maintaining consistency of a shared space across multiple endpoints in a peer-to-peer collaborative computer system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2446283A1 true CA2446283A1 (en) | 2004-04-24 |
| CA2446283C CA2446283C (en) | 2009-12-22 |
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| Application Number | Title | Priority Date | Filing Date |
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| DE60312624D1 (en) | 2007-05-03 |
| DE60312624T2 (en) | 2007-11-29 |
| KR20040036633A (en) | 2004-04-30 |
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| US8073905B2 (en) | 2011-12-06 |
| EP1418726A2 (en) | 2004-05-12 |
| US20070255787A1 (en) | 2007-11-01 |
| IL158508A (en) | 2008-11-03 |
| EP1418726A3 (en) | 2005-06-01 |
| CA2446283C (en) | 2009-12-22 |
| EP1418726B1 (en) | 2007-03-21 |
| KR101021399B1 (en) | 2011-03-14 |
| ATE357700T1 (en) | 2007-04-15 |
| US20040083263A1 (en) | 2004-04-29 |
| IL158508A0 (en) | 2004-05-12 |
| US7340502B2 (en) | 2008-03-04 |
| JP2004152289A (en) | 2004-05-27 |
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