Mystery Number Four - Computational Linguistics and Talking Robots - page 79

may be bound to during match-
ing are restricted by the co-domains of these variables: the restricted variable
α

In the rule, the possible values which α and β

generalizes the summary-creating inference to different kinds of accidents,
e.g., car accident, truck accident, etc., while the restricted variable

limits the
objects to be hit to trees, rocks, etc., as well as cars, trucks, etc. Any content
represented by the proplet hit with a subject and an object proplet satisfying
the variable restrictions of

β

, respectively, will be automatically (i) sum-
marized as an accident of a certain kind where (ii) the summary is related to
the summarized by means of an address value, here (car 1) , thus fulfilling the
condition that the data in a content-addressable memory not be modified.
By summarizing content into shorter and shorter versions, there emerges a
hierarchy providing retrieval relations for upward or downward traversal (Sect.
6.5). Upward traversal supplies the agent with more general notions at a higher
level of abstraction, while downward traversal supplies more concrete instan-
tiations at a lower level of abstraction. Either kind may be used to access and
to apply inferences defined at another level of abstraction, and to subsequently
return to the original level.

α and β

5.4 Subactivation and Intersection

The amount of data in the agent's memory may be very large. For efficiently
finding contents in memory which match the agent's current situation DBS in-
troduces a database mechanism called subactivation . It is a kind of guided as-
sociation, which continuously accompanies the agent's current cognition with
corresponding content stored in the Word Bank.
Subactivation works like a dragnet, pulled by the concepts activated by the
agent's current recognition and inferencing, and providing them with relevant
experiences and knowledge from the agent's past. As a form of association, 11
subactivation results in a mild form of selective attention.
Intuitively, subactivation may be viewed as highlighting an area of content
at half-strength, setting it off against the rest of the Word Bank, but such that
exceptional evaluations are still visible as brighter spots. In this way, the agent
will be alerted to potential threats or opportunities even in current situations
which would otherwise seem innocuous.
An elementary subactivation consists of three steps and may be of a a pri-
mary and a secondary degree. The first step is subactivating the token line

11 Such as associating a certain place with a happy or an unhappy memory.