A preliminary quasimode-based interface for Fenfire and Loom

Author: Benja Fallenstein
Date: 2003-02-17
Revision: 1.1
Last-Modified:2003-03-22
Type:User Interface
Scope:Major
Status: Current

Modes create mode errors. I've witnessed this in Gzz many times, where users would try to type text into a cell while in the wrong mode, creating a huge mess. Research indicates that even sophisticated users cannot keep track of modes always. When commands have habituated so that you do them without having to think about them, you cannot keep track of modes.

Research also indicates that quasimodes never create mode errors. A quasimode is a mode that is in effect while some indicator switch is physically activated. For keyboard interaction, this means "while a modifier key is held down".

The proposal below is a keyboard language for Loom 0.2, the "usable RDF editor" release, based on quasimodes. After experience with this release, we will re-evaluate the keyboard language.

Specification

Text entered without pressing a modifier is simply normal text input. It goes where the text cursor is. If there is no text cursor, one is created at the end of the currently focused node or literal.

The Left and Right keys are used to move the text cursor. If there is no text cursor, Left creates one at the beginning and Right creates one at the end of the text in the focused node or literal.

Alt is used for the movement quasimode. That is, while you hold down Alt (and no other modifier), you can move around in the structure using the arrowsets known from zzstructure. Our arrowsets are 9-key: we have uiojkln,. and wersdfxcv. This allows convenient rotation of the wheel view.

Pressing Shift while Alt is held down enters a special command quasimode. The first key pressed after Shift specifies a command; the interpretation of the following keys depends on the command, but generally they are interpreted as arrow arguments to the command. For example, "N <dir>" may create a new node in the given direction, and "H <dir>" may hop in the given direction.

While in this command quasimode, we can give as many arrows as we like. In a sense, this allows us to have quasimodes for New, Hop and so on. The quasimode is in effect until Shift is released.

For now, the important commands we need are creating nodes and making and breaking connections. In order to create arbitrary connections, we also need to be able to mark resources. I suggest the following bindings:

Command mode, N <dir> [<dir> <dir>...]
Create a new node in the given direction. (We have a property setting specifying which property is used.) The node will be assigned a URN-5. If <dir> is left or right, we move onto the new node. If <dir> is a diagonal direction, we do not change the focus, but select the new node.
Command mode, B <dir> [<dir> <dir>...]
Break the connection in the given direction. Only works with left and right.
Command mode, M [<dir> <dir>...]
Marks the current node. The mark is set, not toggled; if there is a mark already, nothing happens. While in mark mode, giving left/right directions moves the focus and marks the newly focused node. Giving diagonal directions rotates the wheel, but doesn't mark anything.
Command mode, C <dir>
Connect the marked nodes in the given direction. To determine the property, the same setting as for new nodes is used.
Command mode, U [<dir> <dir>...]
Like M, but unmarks; i.e., it removes marks where M adds them.
Esc
Removes all marks.

For mouse-based interaction, we'll have menu items, "New node (Left)," "New node (Right)," "Break connection (Left)," "Connect marked (Right)" and so on.

- Benja