System and method for generating file updates for files stored on read-only media

• US 6,604,236 B1
• Filed: 06/28/1999
• Issued: 08/05/2003
• Est. Priority Date: 06/30/1998
• Status: Expired due to Fees

• Current Assignee: Iora Limited (Infonic Plc)
• Original Assignee: Iora Limited (Infonic Plc)
• Inventors: Falls, Patrick Terence, Draper, Stephen Peter Willis, Collins, Brian James
• Primary Examiner(s): Chaki, Kakali
• Assistant Examiner(s): Chavis, John Q.
• Application Number:
  US09/340,411
• Time in Patent Office: 1,499 Days
• Field of Search: 717/11, 717/170, 717/173
• US Class Current: 717/170
• CPC Class Codes: G01C 21/3859 Differential updating map data
• CPC Class Codes: G06F 16/116 Details of conversion of file system types or formats
• CPC Class Codes: G06F 16/1756 based on delta files
• CPC Class Codes: G06F 8/658 Incremental updates; Differential updates
• CPC Class Codes: G06F 8/66 of program code stored in read-only memory [ROM]

Abstract

A method and system of the present invention generates a representation of a new version of an original file system with reference to the original file system and the new version of the file system. Use of data from previous versions of the file system reduces the amount of data to be stored in the delta directory map file, delta modification data block file, and delta look up table generated for the data portions unique to the newest version of an original file system. The inventive process produces delta data block records that identify the location of data portions that may be used to generate the newest version of the file system. The data portions may be located in a file in the original file system, a delta modification data block file in a previous version of the original file system or a delta modification data block file for the newest version of the original file system.

The method of the present invention is performed by generating a basis index table identifying the data content of an original file system, generating a file of modification data blocks that may be used to modify the data content of the original file system, and generating a delta look up table that identifies the location of the data blocks used to represent the newest version of the original file system. The delta look up table and the file of modification data blocks may be stored for delivery to a computer on which a copy of the original file system is stored. The delta look up table and the file of modification data blocks are then used by the computer system on which a copy of the original file system is stored to provide the data content for a new version of the original file system. This is done in way that appears to provide a single file system containing the new version of the file system. Thus, the method of the present invention may be used to generate data for updating the content of a copy of the original file system without having to generate a copy of every file and data block for the new content of the original file system.

Claims

1. A method for representing modifications to a set of data objects comprising:

generating a baseline of a first version of a set of data objects;

identifying the differences between a second version of the set of data objects and the first version of the set of data objects by;

comparing meta-data for data objects in the second version of the set of data objects to meta-data for data objects in said baseline to determine whether a data object in said second version of said set of data objects is a new data object or a modified data object;

comparing meta-data for data objects in said baseline to meta-data for data objects in said second version of said data objects to determine whether one of said data objects in said first version of said data objects is absent in said second set of said data objects;

wherein said meta-data for data objects in the first version of the set of data objects are stored in a basis directory entry meta-data table, and wherein said meta-data for data objects in the second version of the set of data objects are stored in a delta directory entry meta-data table;

generating update information corresponding to the identified differences, said update information including references to segmented portions of said baseline that correspond to said identified differences regardless of location of said segmented portions in said baseline; and

storing the update information whereby the update information may be retrieved and used to generate the second version of the set of data objects from the first version of the set of data objects.

2. A method for representing modifications to a set of data objects comprising:

generating a baseline of a first version of a set of data objects;

identifying the differences between a second version of the set of data objects and the first version of the set of data objects by;

comparing meta-data for data objects in the second version of the set of data objects to meta-data for data objects in said baseline to determine whether a data object in said second version of said set of data objects is a new data object or a modified data object; and

comparing meta-data for data objects in said baseline to meta-data for data objects in said second version of said data objects to determine whether one of said data objects in said first version of said data objects is absent in said second set of said data objects;

wherein said meta-data for data objects in the first version of the set of data objects are stored in a basis directory entry meta-data table, and wherein said meta-data for data objects in the second version of the set of data objects are stored in a delta directory entry meta-data table;

generating a delta look-up table;

generating a delta directory map file from said delta directory entry meta-data table and said delta look-up table;

storing the update information whereby the update information may be retrieved and used to generate the second version of the set of data objects from the first version of the set of data objects.

3. A method for representing modifications to a set of data objects comprising:

generating a baseline of a first version of a set of data objects;

identifying the differences between a second version of the set of data objects and the first version of the set of data objects;

generating update information corresponding to the identified differences, said update information including references to segmented portions of said baseline that correspond to said identified differences regardless of location of said segmented portions in said baseline;

generating an iterative checksum from a segmented portion of said second version of the set of data objects;

generating a safe checksum from said segmented portion of said second version of the set of data objects;

forming an identifier from said iterative checksum and said safe checksum; and

storing each said identifier for each said segmented portion in said second version.

4. A method for representing modifications to a set of data objects comprising:

generating a baseline of a first version of a set of data objects;

identifying the differences between a second version of the set of data objects and the first version of the set of data objects by;

segmenting data objects in said second version;

comparing an iterative checksum for a segmented portion in said second version of said set of data objects to an iterative checksum for a segmented portion in said baseline;

comparing a safe checksum for said segmented portion in said second version of said set of data objects to a safe checksum for said segmented portion in said baseline in response to said iterative checksum comparison indicating said iterative checksums correspond;

generating update information corresponding to the identified differences, said update information comprising a data block and a corresponding identifier for each said segmented portion in said second version for which no corresponding segmented portion was identified in said baseline;

storing the update information whereby the update information may be retrieved and used to generate the second version of the set of data objects from the first version of the set of data objects.

5. A method for representing modifications to a set of data objects, comprising:

generating at least one basis table, wherein at least one basis table identifies content of a first version of a set of data objects;

identifying differences between the first version of the set of data objects and a second version of the set of data objects by;

comparing an iterative checksum for at least one data block of the second version of the set of data objects to an iterative checksum in a basis table;

comparing a safe checksum for at least one data block of the second version of the set of data objects to a safe checksum in a basis table in response to the iterative checksum comparison indicating that the iterative checksums correspond;

generating update information corresponding to the identified differences; and

storing at least a portion of the update information such that at least a portion of the update information can be retrieved and used with the first version of the set of data objects to generate the second version of the set of data objects.

6. The method of claim 5, wherein the update information comprises at least one reference to a data object of the first version of the set of data objects.

7. The method of claim 5, wherein generating at least one basis table comprises:

selecting a data object of the first version of the set of data objects;

determining whether the content of at least one data block is unique with respect to other data blocks previously selected from the first version of the set of data objects.

8. The method of claim 7, wherein generating at least one basis table further comprises generating and storing identifying data corresponding to the identity of the selected data object.

9. The method of claim 7, wherein generating at least one basis table further comprises segmenting the selected data object into data blocks to form segmented portions.

10. The method of claim 9, wherein segmenting the selected data object comprises forming data blocks of a fixed length.

11. The method of claim 5, wherein generating at least one basis table comprises:

selecting a data object of the first version of the set of data objects;

determining whether the content of at least one data block is unique with respect to other data blocks previously selected from the first version of the set of data objects;

if a data block is unique, storing data identifying the content of the data block and the location of the data block within the selected data object to form at least one entry in at least one basis table; and

continuing the selection, determination and storing of data for data blocks within the data objects of the first version of the set of data objects to generate at least one basis table.

12. The method of claim 11, wherein the selection, determination and storing of data for data blocks within the data objects of the first version of the set of data objects continues until all of the data objects within the first version of the set of data objects have been selected.

13. The method of claim 5, wherein generating at least one basis table comprises:

selecting a data object of the first version of the set of data objects;

generating and storing identifying data corresponding to the identity of the selected data object;

segmenting the selected data object into data blocks to from segmented portions;

determining whether the content of at least one data block is unique with respect to other data blocks previously selected from the first version of the set of data objects;

if a data block is unique, storing data identifying the content of the data block and the location of the data block within the selected data object to form at least one entry in at least one basis table; and

continuing the selection, generation, segmentation, determination and storing of data for data blocks within the data objects of the first version of the set of data objects to generate at least one basis table.

14. The method of claim 5, wherein at least one basis table comprises a basis index data block table file system map, and wherein the basis index data block table file system map comprises data identifying content and location of at least one unique data block of the first version of the set of data objects.

15. The method of claim 5, wherein at least one basis table comprises a basis directory entry meta-data table, and wherein the basis directory entry meta-data table comprises identifying data corresponding to at least one data object in the first version of the set of data objects.

16. The method of claim 5, wherein at least one basis table comprises a basis index data block table file system map, and wherein the basis index data block table file system map comprises data identifying content and location of each unique data block of the first version of the set of data objects.

17. The method of claim 5, wherein at least one basis table comprises at least one basis directory entry meta-data table, and wherein at least one basis directory entry meta-data table comprises identifying data corresponding to each data object in the first version of the set of data objects.

18. The method of claim 5, wherein generating update information comprises generating a delta modification data block file comprising at least a portion of at least one data object of the second version of the set of data objects, and wherein the portion of at least one data object of the second version of the set of data objects corresponds to data not present in the first version of the set of data objects.

19. The method of claim 5, wherein generating update information comprises generating a delta look-up table comprising at least one reference to a location of at least one data block needed to generate the second version of the set of data objects.

20. The method of claim 5, wherein at least one basis table comprises a basis directory entry meta-data table comprising meta-data for data objects in the first version of the set of data objects.

21. The method of claim 5, further comprising generating a delta directory entry meta-data table wherein the delta directory entry meta-data table comprises meta-data for data objects in the second version of the set of data objects.

22. The method of claim 5, further comprising generating a delta directory map file comprising a modification status for at least one data object in the second version of the set of data objects after identifying the differences between the first and second versions of the set of data objects.

23. The method of claim 5, further comprising generating at least one delta directory map file after identifying differences between the first and second versions of the set of data objects, wherein at least one delta directory map file comprises a modification status for at least one data object.

24. The method of claim 5, further comprising generating at least one delta directory map file after identifying differences between the first and second versions of the set of data objects, wherein at least one delta directory map file comprises meta-data for at least one data object.

25. The method of claim 5, further comprising generating at least one delta directory map file after identifying differences between the first and second versions of the set of data objects, wherein at least one delta directory map file comprises a location of a first look up table record for at least one data object, and wherein at least one delta directory map file comprises a number of look up table records needed to construct at least one data object in the second version of the set of data objects.

26. The method of claim 5, further comprising storing content of at least one data block of the second version of the set of data objects in at least one delta table, wherein at least one data block of the second version for which the content is stored has no corresponding data block identified in a basis table.

27. The method of claim 5, wherein identifying differences between the first version of the set of data objects and the second version of the set of data objects further comprises identifying at least one contiguous set of data blocks in the second version of the set of data objects that corresponds to at least one contiguous set of data blocks in at least one basis table.

28. The method of claim 5, further comprising:

identifying differences between a new version of the set of data objects and a combination of at least one basis table and update information for at least one intervening version of the set of data objects;

generating new update information corresponding to the identified differences; and

storing the new update information such that the new update information can be retrieved and used with the first version of the set of data objects to generate the new version of the set of data objects.

29. The method of claim 28, wherein the new update information is stored such that at least one segmented portion of the new version of the set of data objects that is present in the first version of the set of data objects or in at least one intervening version of the set of data objects is not stored in the new update information.

30. A representation of modifications to a set of data objects created by the method of claim 5.

31. A method for representing modifications to a set of data objects, comprising:

generating at least one basis table, wherein at least one basis table identifies content of a first version of a set of data objects;

identifying differences between the first version of the set of data objects and a second version of the set of data objects by identifying whether at least one data block of the second version of the set of data objects corresponds to at least one data block of a basis table;

forming an identifier of at least one data block of the second version of the set of data objects, wherein at least one data block of the second version for which the identifier is formed has no corresponding data block identified in a basis table, wherein forming the identifier comprises;

generating an iterative checksum from a data block;

generating a safe checksum from the data block; and

forming the identifier from the iterative checksum and the safe checksum;

storing the formed identifier in at least one delta table;

generating update information corresponding to the identified differences; and

storing at least a portion of the update information such that at least a portion of the update information can be retrieved and used with the first version of the set of data objects to generate the second version of the set of data objects.

32. The method of claim 31, wherein the update information comprises at least one reference to a data object of the first version of the set of data objects.

33. The method of claim 31, wherein generating at least one basis table comprises:

selecting a data object of the first version of the set of data objects;

determining whether the content of at least one data block is unique with respect to other data blocks previously selected from the first version of the set of data objects.

34. The method of claim 33, wherein generating at least one basis table further comprises generating and storing identifying data corresponding to the identity of the selected data object.

35. The method of claim 33, wherein generating at least one basis table further comprises segmenting the selected data object into data blocks to form segmented portions.

36. The method of claim 35, wherein segmenting the selected data object comprises forming data blocks of a fixed length.

37. The method of claim 33, wherein generating at least one basis table comprises:

selecting a data object of the first version of the set of data objects;

determining whether the content of at least one data block is unique with respect to other data blocks previously selected from the first version of the set of data objects;

if a data block is unique, storing data identifying the content of the data block and the location of the data block within the selected data object to form at least one entry in at least one basis table; and

continuing the selection, determination and storing of data for data blocks within the data objects of the first version of the set of data objects to generate at least one basis table.

38. The method of claim 37, wherein the selection, determination and storing of data for data blocks within the data objects of the first version of the set of data objects continues until all of the data objects within the first version of the set of data objects have been selected.

39. The method of claim 31, wherein generating at least one basis table comprises:

selecting a data object of the first version of the set of data objects;

generating and storing identifying data corresponding to the identity of the selected data object;

segmenting the selected data object into data blocks to from segmented portions;

determining whether the content of at least one data block is unique with respect to other data blocks previously selected from the first version of the set of data objects;

if a data block is unique, storing data identifying the content of the data block and the location of the data block within the selected data object to form at least one entry in at least one basis table; and

continuing the selection, generation, segmentation, determination and storing of data for data blocks within the data objects of the first version of the set of data objects to generate at least one basis table.

40. The method of claim 31, wherein generating update information comprises generating a delta modification data block file comprising at least a portion of at least one data object of the second version of the set of data objects, and wherein the portion of at least one data object of the second version of the set of data objects corresponds to data not present in the first version of the set of data objects.

41. The method of claim 31, further comprising:

identifying differences between a new version of the set of data objects and a combination of at least one basis table and update information for at least one intervening version of the set of data objects;

generating new update information corresponding to the identified differences; and

storing the new update information such that the new update information can be retrieved and used with the first version of the set of data objects to generate the new version of the set of data objects.

42. The method of claim 41, wherein the new update information is stored such that at least one segmented portion of the new version of the set of data objects that is present in the first version of the set of data objects or in at least one intervening version of the set of data objects is not stored in the new update information.

43. A representation of modifications to a set of data objects created by the method of claim 31.

44. A method of modifying a first set of data objects with data from a second set of data objects, comprising:

segmenting at least one data object of a first set of data objects into two or more data blocks;

comparing at least one checksum of a first data block to at least one checksum of at least one second data block to determine distinct data blocks;

preparing at least one basis table comprising at least one entry corresponding to at least one distinct data block;

determining at least one matching data block from a second set of data objects, wherein a matching data block comprises a data block of the second set of data objects that is substantially the same as one of the distinct data blocks of at least one basis table; and

referencing at least one matching data block from the second set of data objects to a corresponding distinct data block of the first set of data objects to prepare a representation of the second set of data objects.

45. The method of claim 44, wherein the first set of data objects comprises one or more files stored in a non-modifiable memory.

46. The method of claim 44, wherein determining at least one matching data block comprises comparing at least one data block of the second set of data objects to at least one entry in at least one basis table to determine if at least one data block of the second set of data objects is the same as one of the distinct data blocks.

47. The method of claim 44, wherein determining at least one matching data block comprises determining whether at least one data object of the second set of data objects does not correspond to a data object of the first set of data objects.

48. The method of claim 44, wherein referencing at least one matching data block from the second set of data objects to a corresponding distinct data block of the first set of data objects comprises generating at least one delta table, wherein at least one delta table comprises at least one reference to at least one distinct data block of the first set of data objects corresponding to at least one matching data block of the second set of data objects.

49. The method of claim 48, wherein at least one delta table further comprises at least one reference to at least one data block of the second set of data objects that is not a matching data block.

50. The method of claim 44, wherein preparing a representation of the second set of data objects comprises preparing at least one file of modification data blocks comprising at least one data block of the second set of data objects that is not a matching data block.

51. The method of claim 44, wherein the first set of data objects comprises a file system hierarchy.

52. The method of claim 44, wherein the combination of the first set of data objects and the representation of the second set of data objects comprises data objects needed to generate contents of the second set of data objects, and data objects needed to construct a hierarchy of the second set of data objects.

53. The method of claim 44, wherein the second set of data objects comprises an update to the first set of data objects, and wherein the method further comprises determining whether at least one data object of the first set of objects is deleted in the second set of data objects.

54. The method of claim 44, further comprising providing data in response to a data access command, wherein the data is provided from a combination of the first set of data objects and the representation of the second set of data objects.

55. The method of claim 44, further comprising receiving a file structure query regarding the second set of data objects;

and directing the file structure query to the representation of the second set of data objects.

56. A representation of a set of data objects created by the method of claim 44.

57. A method of modifying a first set of data objects with data from a second set of data objects, comprising:

segmenting at least one data object of a first set of data objects into two or more data blocks;

determining distinct data blocks from the first set of data objects, wherein determining distinct data blocks comprises, for at least two data blocks;

determining an iterative checksum;

determining a safe checksum; and

determining whether the iterative checksum and the safe check sum of at least one data block match an iterative checksum and a safe checksum of at least one other data block;

preparing at least one basis table comprising at least one entry corresponding to at least one distinct data block;

determining at least one matching data block from a second set of data objects, wherein a matching data block comprises a data block of the second set of data objects that is substantially the same as one of the distinct data blocks of at least one basis table; and

referencing at least one matching data block from the second set of data objects to a corresponding distinct data block of the first set of data objects to prepare a representation of the second set of data objects.

58. The method of claim 57, wherein the first set of data objects comprises one or more files stored in a non-modifiable memory.

59. The method of claim 57, wherein determining at least one matching data block comprises comparing at least one data block of the second set of data objects to at least one entry in at least one basis table to determine if at least one data block of the second set of data objects is the same as one of the distinct data blocks.

60. The method of claim 57, wherein determining at least one matching data block comprises determining whether at least one data object of the second set of data objects does not correspond to a data object of the first set of data objects.

61. The method of claim 57, wherein referencing at least one matching data block from the second set of data objects to a corresponding distinct data block of the first set of data objects comprises generating at least one delta table, wherein at least one delta table comprises at least one reference to at least one distinct data block of the first set of data objects corresponding to at least one matching data block of the second set of data objects.

62. The method of claim 61, wherein at least one delta table further comprises at least one reference to at least one data block of the second set of data objects that is not a matching data block.

63. The method of claim 57, wherein preparing a representation of the second set of data objects comprises preparing at least one file of modification data blocks comprising at least one data block of the second set of data objects that is not a matching data block.

64. The method of claim 57, wherein the first set of data objects comprises a file system hierarchy.

65. The method of claim 57, wherein the combination of the first set of data objects and the representation of the second set of data objects comprises data objects needed to generate contents of the second set of data objects, and data objects needed to construct a hierarchy of the second set of data objects.

66. The method of claim 57, wherein the second set of data objects comprises an update to the first set of data objects, and wherein the method further comprises determining whether at least one data object of the first set of objects is deleted in the second set of data objects.

67. The method of claim 57, further comprising providing data in response to a data access command, wherein the data is provided from a combination of the first set of data objects and the representation of the second set of data objects.

68. The method of claim 57, further comprising receiving a file structure query regarding the second set of data objects;

and directing the file structure query to the representation of the second set of data objects.

69. A representation of a set of data objects created by the method of claim 57.

70. A method of modifying a first set of data objects with data from a second set of data objects, comprising:

generating at least one basis table, wherein at least one basis table comprises a basis index table comprising a location, a size, and a checksum value for at least one distinct data block of a first set of data objects;

determining at least one matching data block from a second set of data objects, wherein a matching data block comprises a data block of the second set of data objects that is substantially the same as one of the distinct data blocks of at least one basis table; and

referencing at least one matching data block from the second set of data objects to a corresponding distinct data block of the first set of data objects to prepare a representation of the second set of data objects.

71. The method of claim 70, wherein the first set of data objects comprises one or more files stored in a non-modifiable memory.

72. The method of claim 70, wherein determining at least one matching data block comprises comparing at least one data block of the second set of data objects to at least one entry in at least one basis table to determine if at least one data block of the second set of data objects is the same as one of the distinct data blocks.

73. The method of claim 70, wherein determining at least one matching data block comprises determining whether at least one data object of the second set of data objects does not correspond to a data object of the first set of data objects.

74. The method of claim 70, wherein referencing at least one matching data block from the second set of data objects to a corresponding distinct data block of the first set of data objects comprises generating at least one delta table, wherein at least one delta table comprises at least one reference to at least one distinct data block of the first set of data objects corresponding to at least one matching data block of the second set of data objects.

75. The method of claim 74, wherein at least one delta table further comprises at least one reference to at least one data block of the second set of data objects that is not a matching data block.

76. The method of claim 70, wherein preparing a representation of the second set of data objects comprises preparing at least one file of modification data blocks comprising at least one data block of the second set of data objects that is not a matching data block.

77. The method of claim 70, wherein the first set of data objects comprises a file system hierarchy.

78. The method of claim 70, wherein the combination of the first set of data objects and the representation of the second set of data objects comprises data objects needed to generate contents of the second set of data objects, and data objects needed to construct a hierarchy of the second set of data objects.

79. The method of claim 70, wherein the second set of data objects comprises an update to the first set of data objects, and wherein the method further comprises determining whether at least one data object of the first set of objects is deleted in the second set of data objects.

80. The method of claim 70, further comprising providing data in response to a data access command, wherein the data is provided from a combination of the first set of data objects and the representation of the second set of data objects.

81. The method of claim 70, further comprising receiving a file structure query regarding the second set of data objects;

and directing the file structure query to the representation of the second set of data objects.

82. A representation of a set of data objects created by the method of claim 70.

83. A method of modifying a first set of data objects with data from a second set of data objects, comprising:

storing at least one checksum for at least one distinct data block from a first set of data objects in at least one basis table;

determining an iterative checksum for at least one data block of a second set of data objects;

determining whether the iterative checksum for at least one data block of the second set of data objects matches an iterative checksum in at least one basis table, wherein a matching data block comprises a data block of the second set of data objects that is substantially the same as one of the distinct data blocks of at least one basis table; and

referencing at least one matching data block from the second set of data objects to a corresponding distinct data block of the first set of data objects to prepare a representation of the second set of data objects.

84. The method of claim 83, wherein the first set of data objects comprises one or more files stored in a non-modifiable memory.

85. The method of claim 83, wherein referencing at least one matching data block from the second set of data objects to a corresponding distinct data block of the first set of data objects comprises generating at least one delta table, wherein at least one delta table comprises at least one reference to at least one distinct data block of the first set of data objects corresponding to at least one matching data block of the second set of data objects.

86. The method of claim 85, wherein at least one delta table further comprises at least one reference to at least one data block of the second set of data objects that is not a matching data block.

87. The method of claim 83, wherein preparing a representation of the second set of data objects comprises preparing at least one file of modification data blocks comprising at least one data block of the second set of data objects that is not a matching data block.

88. The method of claim 83, wherein the first set of data objects comprises a file system hierarchy.

89. The method of claim 83, wherein the combination of the first set of data objects and the representation of the second set of data objects comprises data objects needed to generate contents of the second set of data objects, and data objects needed to construct a hierarchy of the second set of data objects.

90. The method of claim 83, wherein the second set of data objects comprises an update to the first set of data objects, and wherein the method further comprises determining whether at least one data object of the first set of objects is deleted in the second set of data objects.

91. The method of claim 83, further comprising providing data in response to a data access command, wherein the data is provided from a combination of the first set of data objects and the representation of the second set of data objects.

92. The method of claim 83, further comprising receiving a file structure query regarding the second set of data objects;

and directing the file structure query to the representation of the second set of data objects.

93. A representation of a set of data objects created by the method of claim 83.

94. A method of modifying a first set of data objects with data from a second set of data objects, comprising:

storing at least one checksum for at least one distinct data block from a first set of data objects in at least one basis table;

determining an iterative checksum for at least one data block of a second set of data objects;

determining whether the iterative checksum for at least one data block of the second set of data objects matches an iterative checksum in at least one basis table;

comparing a safe checksum for at least one data block of the second set of data objects with an safe checksum that matches an iterative checksum of at least one basis table;

determining whether the safe checksum for at least one data block of the second set of data objects matches a safe checksum corresponding to the matched iterative checksum in at least one basis table; and

referencing at least one matching data block from the second set of data objects to a corresponding distinct data block of the first set of data objects to prepare a representation of the second set of data objects, wherein a matching data block comprises a data block of the second set of data objects that is substantially the same as one of the distinct data blocks of at least one basis table.

95. The method of claim 94, wherein the first set of data objects comprises one or more files stored in a non-modifiable memory.

96. The method of claim 94, wherein referencing at least one matching data block from the second set of data objects to a corresponding distinct data block of the first set of data objects comprises generating at least one delta table, wherein at least one delta table comprises at least one reference to at least one distinct data block of the first set of data objects corresponding to at least one matching data block of the second set of data objects.

97. The method of claim 96, wherein at least one delta table further comprises at least one reference to at least one data block of the second set of data objects that is not a matching data block.

98. The method of claim 94, wherein preparing a representation of the second set of data objects comprises preparing at least one file of modification data blocks comprising at least one data block of the second set of data objects that is not a matching data block.

99. The method of claim 94, wherein the first set of data objects comprises a file system hierarchy.

100. The method of claim 94, wherein the combination of the first set of data objects and the representation of the second set of data objects comprises data objects needed to generate contents of the second set of data objects, and data objects needed to construct a hierarchy of the second set of data objects.

101. The method of claim 94, wherein the second set of data objects comprises an update to the first set of data objects, and wherein the method further comprises determining whether at least one data object of the first set of objects is deleted in the second set of data objects.

102. The method of claim 94, further comprising providing data in response to a data access command, wherein the data is provided from a combination of the first set of data objects and the representation of the second set of data objects.

103. The method of claim 94, further comprising receiving a file structure query regarding the second set of data objects;

and directing the file structure query to the representation of the second set of data objects.

104. A representation of a set of data objects created by the method of claim 94.

105. A method of modifying a first set of data objects with data from a second set of data objects, comprising:

generating at least one basis table identifying distinct data blocks from a first set of data objects;

determining at least one matching data block from a second set of data objects, wherein a matching data block comprises a data block of the second set of data objects that is substantially the same as one of the distinct data blocks of at least one basis table;

referencing at least one matching data block from the second set of data objects to a corresponding distinct data block of the first set of data objects;

preparing at least one file of modification data blocks comprising at least one data block of the second set of data objects that is not a matching data block;

preparing at least one delta look up table entry comprising at least one reference to at least one data block in at least one file of modification data blocks; and

preparing at least one delta look up table entry comprising at least one reference to at least one data block of the first set of data objects;

wherein two or more of the referenced data blocks are combinable to generate the second set of data objects.

106. The method of claim 105, wherein the first set of data objects comprises one or more files stored in a non-modifiable memory.

107. The method of claim 105, wherein determining at least one matching data block comprises comparing at least one data block of the second set of data objects to at least one entry in at least one basis table to determine if at least one data block of the second set of data objects is the same as one of the distinct data blocks.

108. The method of claim 105, wherein determining at least one matching data block comprises determining whether at least one data object of the second set of data objects does not correspond to a data object of the first set of data objects.

109. The method of claim 105, wherein the first set of data objects comprises a file system hierarchy.

110. The method of claim 105, wherein the combination of the first set of data objects and the representation of the second set of data objects comprises data objects needed to generate contents of the second set of data objects, and data objects needed to construct a hierarchy of the second set of data objects.

111. The method of claim 105, wherein the second set of data objects comprises an update to the first set of data objects, and wherein the method further comprises determining whether at least one data object of the first set of objects is deleted in the second set of data objects.

112. The method of claim 105, further comprising providing data in response to a data access command, wherein the data is provided from a combination of the first set of data objects and the representation of the second set of data objects.

113. The method of claim 105, further comprising receiving a file structure query regarding the second set of data objects;

and directing the file structure query to the representation of the second set of data objects.

114. A representation of a set of data objects created by the method of claim 105.

115. A method of modifying a first set of data objects with data from a second set of data objects, comprising:

generating at least one basis table identifying distinct data blocks from a first set of data objects;

determining at least one matching data block from a second set of data objects, wherein a matching data block comprises a data block of the second set of data objects that is substantially the same as one of the distinct data blocks of at least one basis table;

referencing at least one matching data block from the second set of data objects to a corresponding distinct data block of the first set of data objects to prepare a representation of the second set of data objects;

receiving a data access command requesting data from the second set of data objects; and

directing the data access command to the representation of the second set of data objects.

116. The method of claim 115, wherein generating at least one basis table comprises:

segmenting at least one data object of the first set of data objects into two or more data blocks;

determining distinct data blocks from the first set of data objects; and

preparing at least one basis table comprising at least one entry corresponding to at least one distinct data block.

117. The method of claim 116, wherein determining distinct data blocks comprises comparing at least one checksum of a first data block to at least one checksum of at least one second data block.

118. The method of claim 116, wherein determining distinct data blocks comprises:

for at least two data blocks;

determining an iterative checksum;

determining a safe checksum; and

determining whether the iterative checksum and the safe check sum of at least one data block match an iterative checksum and a safe checksum of at least one other data block.

119. The method of claim 115, wherein the first set of data objects comprises one or more files stored in a non-modifiable memory.

120. The method of claim 115, wherein at least one basis table comprises a basis index table comprising at least one entry for at least one distinct data block of the first set of data objects.

121. The method of claim 120, wherein at least one entry in a basis index table comprise a location, a size, and a checksum value for at least one distinct data block.

122. The method of claim 118, wherein at least one basis table comprises a basis directory entry meta-data table comprising at least one entry for at least one data object of the first set of data objects.

123. The method of claim 122, wherein at least one entry in a basis directory entry meta-data table comprises meta-data for at least one data object of the first set of data objects.

124. The method of claim 118, wherein a distinct data block comprises a data block containing data that is not the same as data contained in any other data block of the first set of data objects.

125. The method of claim 118, wherein a distinct data block comprises a single data block that represents all other data blocks that are identical in content.

126. The method of claim 118, wherein a data block comprises a portion of data from a data object having a determined length.

127. The method of claim 118, wherein determining at least one matching data block comprises comparing at least one data block of the second set of data objects to at least one entry in at least one basis table to determine if at least one data block of the second set of data objects is the same as one of the distinct data blocks.

128. The method of claim 118, wherein generating at least one basis table comprises storing at least one checksum for at least one distinct data block in at least one basis table, and wherein determining matching data blocks comprises:

determining an iterative checksum for at least one data block of the second set of data objects; and

determining whether the iterative checksum for at least one data block of the second set of data objects matches an iterative checksum in at least one basis table.

129. The method of claim 128, wherein determining matching data blocks further comprises:

for at least one data block of the second set of data objects with an iterative checksum that matches an iterative checksum of at least one basis table;

determining a safe checksum for the data block of the second set of data objects; and

determining whether the safe checksum for the data block of the second set of data objects matches a safe checksum corresponding to the matched iterative checksum in at least one basis table.

130. The method of claim 115, wherein determining at least one matching data block comprises determining whether at least one data object of the second set of data objects does not correspond to a data object of the first set of data objects.

131. The method of claim 115, wherein referencing at least one matching data block from the second set of data objects to a corresponding distinct data block of the first set of data objects comprises generating at least one delta table, wherein at least one delta table comprises at least one reference to at least one distinct data block of the first set of data objects corresponding to at least one matching data block of the second set of data objects.

132. The method of claim 131, wherein at least one delta table further comprises at least one reference to at least one data block of the second set of data objects that is not a matching data block.

133. The method of claim 115, wherein preparing a representation of the second set of data objects comprises preparing at least one file of modification data blocks comprising at least one data block of the second set of data objects that is not a matching data block.

134. The method of claim 115, wherein preparing a representation of the second set of data objects comprises:

preparing at least one file of modification data blocks comprising at least one data block of the second set of data objects that is not a matching data block;

preparing at least one delta look up table entry comprising at least one reference to at least one data block in at least one file of modification data blocks; and

preparing at least one delta look up table entry comprising at least one reference to at least one data block of the first set of data objects;

wherein two or more of the referenced data blocks are combinable to generate the second set of data objects.

135. The method of claim 115, wherein the first set of data objects comprises a file system hierarchy.

136. The method of claim 115, wherein the first set of data objects comprises a file system hierarchy, wherein the second set of data objects comprises a file system hierarchy, and wherein preparing a representation of the second set of data objects comprises preparing at least one delta directory map file comprising at least one difference between the file system hierarchies of the first and second sets of data objects.

137. The method of claim 115, wherein the first set of data objects comprises a file system hierarchy, wherein the second set of data objects comprises a file system hierarchy, wherein preparing a representation of the second set of data objects comprises preparing at least one delta directory map file comprising at least one difference between the file system hierarchies of the first and second sets of data objects, and wherein at least one delta directory map file and the file system hierarchy of the first set of data objects are combinable to generate the file system hierarchy of the second set of data objects.

138. The method of claim 115, wherein the combination of the first set of data objects and the representation of the second set of data objects comprises data objects needed to generate contents of the second set of data objects, and data objects needed to construct a hierarchy of the second set of data objects.

139. The method of claim 115, wherein the second set of data objects comprises an update to the first set of data objects, and wherein the method further comprises determining whether at least one data object of the first set of objects is deleted in the second set of data objects.

140. The method of claim 115, wherein the second set of data objects comprises an update to the first set of data objects, and wherein the method further comprises:

generating at least one basis directory entry meta-data table comprising meta-data for at least one data object of the first set of data objects;

generating at least one delta directory entry meta-data table comprising meta-data for at least one data object of the second set of data objects;

determine whether at least one data object of the first set of data objects is absent from the second set of data objects; and

if a data object of the first set of data objects is absent from the second set of data objects, adding an entry to at least one delta directory entry meta-data table for the absent data object indicating that the data object is deleted.

141. The method of claim 115, further comprising providing data in response to a data access command, wherein the data is provided from a combination of the first set of data objects and the representation of the second set of data objects.

142. The method of claim 115, further comprising receiving a file structure query regarding the second set of data objects;

and directing the file structure query to the representation of the second set of data objects.

143. A representation of a set of data objects created by the method of claim 115.

144. A method of modifying a first set of data objects with data from a second set of data objects, comprising:

generating at least one basis table identifying distinct data blocks from a first set of data objects;

determining at least one matching data block from a second set of data objects, wherein a matching data block comprises a data block of the second set of data objects that is substantially the same as one of the distinct data blocks of at least one basis table;

referencing at least one matching data block from the second set of data objects to a corresponding distinct data block of the first set of data objects to prepare a representation of the second set of data objects; and

providing data in response to a data access command, wherein the data is provided from a combination of the first set of data objects and the representation of the second set of data objects.

145. The method of claim 144, wherein the first set of data objects comprises one or more files stored in a non-modifiable memory.

146. The method of claim 144, wherein determining at least one matching data block comprises comparing at least one data block of the second set of data objects to at least one entry in at least one basis table to determine if at least one data block of the second set of data objects is the same as one of the distinct data blocks.

147. The method of claim 144, wherein determining at least one matching data block comprises determining whether at least one data object of the second set of data objects does not correspond to a data object of the first set of data objects.

148. The method of claim 144, wherein referencing at least one matching data block from the second set of data objects to a corresponding distinct data block of the first set of data objects comprises generating at least one delta table, wherein at least one delta table comprises at least one reference to at least one distinct data block of the first set of data objects corresponding to at least one matching data block of the second set of data objects.

149. The method of claim 148, wherein at least one delta table further comprises at least one reference to at least one data block of the second set of data objects that is not a matching data block.

150. The method of claim 144, wherein preparing a representation of the second set of data objects comprises preparing at least one file of modification data blocks comprising at least one data block of the second set of data objects that is not a matching data block.

151. The method of claim 144, wherein the first set of data objects comprises a file system hierarchy.

152. The method of claim 144, wherein the combination of the first set of data objects and the representation of the second set of data objects comprises data objects needed to generate contents of the second set of data objects, and data objects needed to construct a hierarchy of the second set of data objects.

153. The method of claim 144, wherein the second set of data objects comprises an update to the first set of data objects, and wherein the method further comprises determining whether at least one data object of the first set of objects is deleted in the second set of data objects.

154. A representation of a set of data objects created by the method of claim 144.

161. The method of claim 154, wherein preparing a representation of the second set of data objects comprises preparing at least one file of modification data blocks comprising at least one data block of the second set of data objects that is not a matching data block.

162. The method of claim 154, wherein the first set of data objects comprises a file system hierarchy.

163. The method of claim 154, wherein the combination of the first set of data objects and the representation of the second set of data objects comprises data objects needed to generate contents of the second set of data objects, and data objects needed to construct a hierarchy of the second set of data objects.

164. A representation of a set of data objects created by the method of claim 154.

155. A method of modifying a first set of data objects with data from a second set of data objects, comprising:

generating at least one basis table identifying distinct data blocks from a first set of data objects;

determining at least one matching data block from a second set of data objects, wherein a matching data block comprises a data block of the second set of data objects that is substantially the same as one of the distinct data blocks of at least one basis table; and

referencing at least one matching data block from the second set of data objects to a corresponding distinct data block of the first set of data objects to prepare a representation of the second set of data objects;

receiving a file structure query regarding the second set of data objects; and

directing the file structure query to the representation of the second set of data objects.

156. The method of claim 155, wherein the first set of data objects comprises one or more files stored in a non-modifiable memory.

157. The method of claim 155, wherein determining at least one matching data block comprises comparing at least one data block of the second set of data objects to at least one entry in at least one basis table to determine if at least one data block of the second set of data objects is the same as one of the distinct data blocks.

158. The method of claim 155, wherein determining at least one matching data block comprises determining whether at least one data object of the second set of data objects does not correspond to a data object of the first set of data objects.

159. The method of claim 155, wherein referencing at least one matching data block from the second set of data objects to a corresponding distinct data block of the first set of data objects comprises generating at least one delta table, wherein at least one delta table comprises at least one reference to at least one distinct data block of the first set of data objects corresponding to at least one matching data block of the second set of data objects.

160. The method of claim 159, wherein at least one delta table further comprises at least one reference to at least one data block of the second set of data objects that is not a matching data block.