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Network/Interactive Activation

Introduction

Interactive activation network boxes contain nodes with associated activation values. Nodes within an interactive activation network may be created or deleted. Existing nodes may be excited or inhibited. Their activation values may also be queried by conditions within processes, and a special purpose dynamically updated viewer allows activations to be monitored during model execution.

The initial contents of an interactive activation network are the set of (names of) nodes initially contained in that network. Initial activation values are set with reference to the box's properties.

Nodes may be added to an interactive activation network at any stage in processing through the use of add actions (e.g., within data sources or rules contained in a process):

Nodes may be deleted from an interactive activation network at any stage in processing through the use of clear actions, delete actions, and delete all actions:

The first of these removes all nodes from a network. The second deletes one node (whose name unifies with NodeName). The third deletes all nodes whose name unify with NodeName.

Interactive activation networks will normally co-exist with a process which sends appropriate excite messages to control the node activations:

In such a message, Excitation should be a numeric quantity which specifies the level of excitation to apply to the node. If the quantity is negative, it will be interpreted as inhibition.

On each processing cycle, the total excitation to each node within the network is summed. This net excitation is then used, along with the current activation and network activation properties to determine the new activation of each node.

In addition to external input, node activations may be subject to internal competition, using Lateral Inhibition and Self Activation. Each of these can be configured by additional properties, allowing them to be enabled separately, scaled appropriately, and to use alternative baselines. Lateral Inhibition may be configured to use any of several different functions, and it may also be calculated over the whole network or within sub-networks which partition the set of nodes in the box into several effectively separate networks.

If Subnet competition is selected within the network's properties, NodeName must be specified as a binary structure using the slash operator ("/"), in which the first argument is the name of the node and the second is the name of the sub-network, e.g., mynode/mysubnet. This node will then only compete with others belonging to the mysubnet sub-network.

The last operation available on networks is matching. The activation value of a node may be queried by matching against the node's name:

The above code segment may occur in the conditions of any rule or condition definition that can read MyNet. Normally Activation will be an uninstantiated variable, and execution of the condition will bind that variable to the activation of the node whose name is bound to Name. As with buffers, the match operation will attempt to re-satisfy if any part of the node definition is uninstantiated.

Properties

Interactive activation networks are highly configurable. A total of sixteen properties govern their behaviour:

The Activation Graph View

Windows corresponding to interactive activation networks include an Activation Graph page in the notebook. This page is a dynamically updated graphical display of node activations. The view shows the activations of nodes as coloured bars. If Subnet competition is selected, different colours are used for different sub-networks.


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