Representing Knowledge in an Uncertain Domain

In Belief Networks:

• nodes represent random variables

• directed link between X and Y implies that X "directly influences" Y

• each node has a conditional probability table (CPT) quantifying the effects that the parents (incoming links) have on the node

• network is a DAG (no directed cycles)

Belief networks:

• only represent what we know

• which summarizes what we don't know
  • reasons alarm doesn't go off

  • reasons John and Mary don't call