A DAG whose vertices are gates of five types:

  1. AND
  2. OR
  3. NOT
  4. Known input (no incoming edges)
  5. Unknown input (no incoming edges) One sink of the DAG is the output gate which we want to be true.

Given a boolean circuit, find a truth assignment for the unknown inputs such that output = true, or determine no assignment exists.

  • This is a well-defined search problem
  • This is a generalization of SAT