On Marker-Passing and Spreading Activation
The links connecting the nodes of the associative network carry information about the relationships between these nodes. These relationships may be uni-or bi-directional depending on type and implementation. One special link, the ISA link, is often distinguished from the others. The isa link defines a hierarchy of types within the network, and usually the semantics of these nets are such tha t properties from the node “ higher” in the isa tree are
inherited by the lower nodes. The typical parent and child node terminology, borrowed from literature on “ trees” in computer science, is usually used to describe these relations.