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Software Patent
of the year 2006

May – Patent 1

EP0621528 – Multiple level Undo/redo mechanism

EU-Patent on software (algorithm)
Application to European Patent Office on 20/04/1994 by Microsoft Corporation (USA)
Granted on 13/06/2001
Date of priority: 22/04/1993 (valid no more than until 22/04/2013)
Patent Attorney: Grünecker, Kinkeldey, Stockmair & Schwanhäusser Anwaltssozietät
Patent specification provided by FFII/Gauss
Patent specification provided by EPO/espacenet

Advice on the reading of patent specifications:

The decisive element are the claims, as they specify which actions are forbidden within the framework of the patent.
Violating one single claim is sufficient to be considered a patent violation. Generally, claim number 1 is the decisive main claim which covers all other claims relating to special cases.
The description is intended to help the reader interpret the claim. At the same time, it is supposed to document and disclose the details of the invention. This disclosure is the original purpose of the entire patent system.
In practice, a patent specification contains no detailed information on how the patented procedure could be implemented (even if the patent owner allowed the implementation). In particular, a software patent contains no program code (reference implementation), but merely describes the idea of a software.

Patented idea: The undo/redo mechanism is standardised through integration of the operating system.

Main claim: The program files a list of the executed user commands in the operating system. The operating system receives the undo/redo user commands signalling the application, if and when user commands are to be undone or redone.

Further claims:

Only undoing or only redoing.
Undoing all at once or redoing all at once.
Storing the moves as a list of objects and/or pointers on undo/redo-functions.
Deactivating the operating elements, if there are no means available for undoing or redoing.

Description: The patent specification describes the natual method of implementing the function "undo user command" and "redo user command", a function supported by numerous application programs (frequently by means of using the control key and the key "Z").

The patented idea refers to accomplishing a uniform performance of the Undo/Redo-function in all computer programs through integration of the operating system.

The patent applied for initially referred to a a multiple level undo/redo mechanism conceived in general terms. It was granted with the qualification of integrating the operating system.

Everyday parallel: If you stay as a tourist in a foreign city you should memorize well the way you are taking ("user commands") in order to find the way back to the hotel ("undo"). If the host ("operating system") provides the tourist with a notepad ("API") both of them infringe the patent. The same is true if the tourist uses the notepad to walk along the same route once the more on the next day ("redo").

For avoiding the patent the tourist should bring along his or her own notepad. However this imlicates that the notepads ("undo") used by all the tourists ("program") all look differently.

Examples for patent infringements: The undo/redo-functionality is used in approximately every computer program designed for processing images, music or text. The algorithm outlined in the patent specification results naturally from the problem. Therefore every computer operating system including an undo/redo-API, infringes the patent. This also applies to the desktop entvironments GNOME and KDE, which are normally regarded as operating systems.

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