...tpimage2.

The words black, blue, red, and green do not appear in the actual interface, but are simply labeled in the paper for black and white printers. A color version of the paper is available from http://www.isi.edu/info-agents/heracles.

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... variable

In the example of Section 2 we have referred to each piece of information presented to the user as a slot. We use the term slot for user interface purposes. Each slot has a corresponding variable defined in the constraint network, but there may be variables that are not presented to the user (see Section 5).

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... lots.

For simplicity we assume in the example that all domain expressions only involve one constraint.

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