Apple has filed a patent applications that describes documents such as spreadsheets, presentations, as well as image and text documents that can be edited, but do not need to be saved by the user.
The patent application does not reveal an ingenious approach that would eliminate the need to save documents altogether, but it assumes that technology can save documents so that the user does not have to. The software itself would save document , while the save event would be triggered by an "elapsed time interval, a pause in user input, a shift of focus away from the document, a closing of the document, a printing of the document, pasting content into the document, deleting content from the document, or formatting the document."
Besides saving the document, the software would also automatically maintain all versions of a edited document and allow a user to use content from different version of a document at the same time. According to the filing, a saveless document increases user convenience, as " the user is not bothered by alerts asking what to do with unsaved document changes when closing documents or terminating applications." In fact, the user can completely ignore save events in the way we are used to them today.
The feature set is reminiscent of a document that is edited in the cloud. However, this particular patent does not relate to cloud services, but locally installed software instead. For those who have used Mac OS X Lion 10.7, you should have a pretty good idea of how this works in practice.