IntervalLink
From OpenCog
The IntervalLink is a Link type used to specify numeric intervals. It would serve as the base type for TimeIntervalLink.
A typical usage might be:
IntervalLink NumberNode 2.0 NumberNode 3.0
which specifies the numeric interval between two and three. An unbounded-above interval can be specified with a negative upper bound:
IntervalLink NumberNode 2.0 NumberNode -1.0
indicates the interval "two or more".
It is intended for use with the typing of the GlobNode, and with the specification of list lengths, in the TypeSetLink.