ABSTRACT
Typically the representation of knowledge units making up cognitive task models takes two forms: declarative knowledge units and procedural knowledge units (Anderson, 1993). These are associated with two types of memory: declarative and procedural. Declarative units represent facts about a domain or relations between objects, such as “Washington was the first president of the United States”. The units of declarative knowledge, which organize objects such as Washington and the United States by way of the relation “president of”, are sometimes referred to as propositions or chunks. Procedural knowledge units, consist of associations of these facts or chunks in specific patterns, which are bound to specific actions. The actions may be overt behavioral actions or covert mental actions, such as retrieving something from memory, deciding between alternatives, setting up a motor response for execution, deleting information from working memory, adding information to working memory, or setting a new goal. These procedural units are referred to as production units or production rules and are characterized by their automaticity. That is, production units are not interpreted but are fired off automatically in sequences, which produce skilled performance. They are automatic to the extent that experts at a specific skill may not be able to recall why they perform the skill as they do. They have lost their ability to interpret their behavior. Theoretically, these different units of knowledge can represent knowledge about any type of task.
