Knowledge representation is an area of artificial intelligence concerned with how knowledge can be represented symbolically and manipulated in an automated way by reasoning programs. It is at the very core of a radical idea about how to understand intelligence: instead of trying to understand or build brains from the bottom up, knowledge representation tries to understand or build intelligent behavior from the top down. In particular, the authors ask what an agent would need to know in order to behave intelligently, and what computational mechanisms could allow this knowledge to be made available to the agent as required.