The network is of the generalized Hopfield type: connections between units are symmetric, and units repeatedly update until the network settles. Each unit has an associated activation function; for most units this is the familiar interactive activation rule [McClelland and Rumelhart, 1981]:
where is the activation of unit i at time t; is the input to i at time t; and , , and are the maximum activation, minimum activation, and decay rate associated with i. All units in the network currently have maximum activations of 1 and minimum activations of 0.
As we noted in Section 3.1.1 above, language makes explicit reference to objects and relations, and a model of the acquisition and processing of language requires a means of representing conceptual objects and relations, as well as the associations between lexical/grammatical patterns and conceptual objects and relations. The network is made up of two kinds of units: Object Units and Relation Units, which serve these two purposes.