In
ACT-R, elements of declarative knowledge are called chunks or WMEs (for working
memory elements). WMEs are intended to represent chunks of knowledge that a
person might be expected to have when they solve a problem. The basic elements
of the representation are types and slots. Although types and
slots can mean anything, one way to understand them is to think of types as
categories (e.g., birds) and slots as category attributes (e.g., color or
size). Below are chunks that encode the facts that the dog chased the cat
and that 4+3=7: The type of the first chunk is chase and
its slots are agent and object. The type of the second chunk is
addition-fact and its slots are addend1, addend2, and
sum