Method and system for allowing multiple users to simultaneously edit a spreadsheet

A computer system, including a program module for allowing simultaneous editing of a spreadsheet stored in a disk file that is accessible by a first computer through a first network connection and a second computer through a second network connection, said disk file including a disk image of said spreadsheet and a disk change log for maintaining a list of changes to said spreadsheet stored in the disk file, said first computer being operative to:

• (a) allow a first user using said first computer to access and edit said spreadsheet over said first network connection to create a first memory image of said spreadsheet and to equate a first session identifier to a current session identifier;
• (b) store said first user's changes in a first memory change log;
• (c) in response to said first user performing a save operation, copy over said first network connection, said first memory change log to said disk change log stored in said disk file and update said current session identifier;
• and
• said second computer being operative to:
• (d) allow a second user using said second computer to access and edit said spreadsheet over said second network connection, simultaneously with said first user to create a second memory image of said spreadsheet and to equate a second session identifier to said current session identifier;
• (e) store said second user's changes in a second memory change log;
• (f) in response to said second user performing a save operation, identify over said second network connection whether any intervening changes from said first user exist in said disk file by comparing said second session identifier to said current session identifier;
• (g) if any intervening changes exist, merge the changes in said second memory change log with said intervening changes;
• (h) copy over said second network connection, said second memory change log to said disk change log;
• and
• (i) update said current session identifier.

A memory storage device for a computer program, said memory storage device storing a computer program that provides a method for simultaneously editing a spreadsheet stored in a disk file of a computer, said disk file including a disk image of said spreadsheet and a disk change log for maintaining a list of changes to said spreadsheet stored in the disk file, said method comprising the steps of:

• (a) allowing a first user using a first computer, said first computer being functionally connected to said computer by a first network connection, to access and edit said spreadsheet over said first network connection to create a first memory image of said spreadsheet;
• (b) storing said first user's changes in a first memory change log;
• (c) in response to performing a save operation, copying over said first network connection, said first memory change log to said disk change log stored in said disk file;
• (d) allowing a second user using a second computer, said second computer being functionally connected to said computer by a second network connection, to access and edit said spreadsheet over said first network connection, simultaneously with said first user to create a second memory image of said spreedsheet;
• (e) storing said second user's changes in a second memory change log;
• and
• (f) in response performing a save operation, identifying, over said first network connection, whether any intervening changes from said first user exist in said disk file, merging the changes in said second memory change log with said intervening changes and storing said merged changes in said second memory change log, and copying said second memory change log over said first network connection to said disk change log.