A HebbianLink between two atoms indicate that these atoms are likely to be important to an OpenCog instance at the same time. So if one atom comes into the AttentionalFocus of the instance, then attention is spread (by the ImportanceSpreadingAgent) to the other in an attempt to get it into the attentional focus as well, or at least to prevent it from being forgotten.
HebbianLinks are discovered by the to-be-implemented HebbianMiningAgent.
HebbianLinks have their weights updated by the HebbianLearningAgent.
Hebbian Link Types
There are three types of HebbianLinks, Symmetric, Asymmetric, and Inverse.
Symmetric Hebbian links are unordered, and represent a symmetric correlation between the atoms connected. Such that, if any of the atoms are in the attentional focus, then all of the others are also likely to be, or should be, in the Attentional focus. They can have any Arity.
Asymmetric Hebbian links are ordered, and represent an asymmetric correlation between the connected atoms. If the source atom is in the Attentional focus the link indicates that the target atom should also be the the the focus, however the reverse is NOT true.
An Inverse Hebbian links is the opposite of an Asymmetric Hebbian links. The inverse link is also ordered, but indicates that if the source atom is in the Attentional focus, then the target atoms should NOT be. This confers the ability of the target atom to essentially steal importance from the target until it is no longer in the attentional focus.
This link was introduced to assist in the dynamics of the Hopfield network emulator but could potentially be useful in other situations too.