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Paper: Time Machine Computing

Time-Machine Computing: A Time-centric Approach for the Information Environment
Jun Rekimoto
Sony CSL

This paper is motivated by observations that many users prefer to use the desktop as a spatial organizational area (Malone), instead of using folders and the like. This leads to the inevitable problem of limited desktop space, which in Malone's research was partially solved with the idea of "piles." Freeman et. al have argued that time-oriented approaches (e.g. e-mail) are superior to pure spatial approaches and proposed a one-dimensional timeline system. Rekimoto expands upon both of these observations by trying to create a two-dimensional timeline system that allows for time-based and spatial cues.

Key features

- Lifelong archiving: all of the users activities are permanently recorded and time-stamped
- Time-travelling: user is able to reconstruct the state of the system at any arbitrary date. This has several implications, perhaps most significantly that deletion of an item is temporal.
- Multiple time visualizations: calendar, timeline
- "Time-casting": applications are able to communicate time metadata to each other


TimeScape is a desktop replacement. The concept of folders is completely replaced with spatial arrangement of objects and time-indexing. Items remain on the desktop until they expire (application dependent) or dragged to the trash can (temporal deletion). In order to retrieve an item previously on the desktop, the time dial can be moved backwards in time. Time travel to the future is also permitted.

Three views were implemented: desktop, timeline, and calendar. Color is used to indicate the state of the display (past/present/future) as well as density of items (in timeline view). In timeline view, items are filtered when zoomed out to limit the clutter. This filtering is based on the duration of the item.

A text-based search is included with "search forward" and "search backward" buttons. The search can also include items that were spatially organized close to the relevant item (e.g. if a photo is next to a document with the search term in it, it will appear as well).

A filter can also be applied to timeline and calendar views to reduce the amount of information displayed.

"Time Casting"

Time-casting is more a design principle than an application. Every application is designed to have a knowledge of "current time" as well as the ability to manipulate "current time" based on a users interaction. For example, clicking on an older e-mail would set the time of my photo program to the same time. Even a text document is annotated with the time that individual characters were created.

This notion of time casting is not limited to a single computer. Rekimoto has demonstrations of using a PDA to cast between an appointment calendar and a desktop.

Finally, the notion of time indexing can also be linked to location if the devices have the appropriate equipment. This would allow users to make queries of the type "when I was in ____."


TmSamba is a modified file system Rekimoto created sa a backend. It logs every transaction made to it. This allows for interesting CVS-like features, such as automated version tracking and diff-ing a document between various dates.

Storage was not a concern in this study and the majority of data indexed was textual. Rekimoto agrees that this approach would have to be modified for more storage-heavy multimedia.

User study

PostIt notes very versatile and popular. They were useful in helping users reconstruct history as well as serve as photo annotations, etc...

Rekimoto had to add the feature to "unlock" the past. Users frequently wanted to create/attach additional data to past items while leaving the past data and time relation intact.

Users were hesitant to remove items from the desktop. Rekimoto proposes automatic removing or shrinking usused items.

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This page contains a single entry from kwc blog posted on May 20, 2003 5:50 PM.

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