Let us remind the reader of two classical notions:
- a model is a simple representation of reality, made for some specific purpose.
- information is what allows a cognitive system (CS) receiving it to build-up or update its own model of some cognitive domain. Information is conveyed by messages. The amount of information conveyed by a message is the logarithm of the inverse of probability of occurence of this message, as estimated in the CS. If the logarithm is taken in base 2, the metric unit is the bit.
Based on these classical notions, new cognitive concepts can be defined.