Directed graphs | Boolean algebra | Graph data structures
Propositional directed acyclic graph
A propositional directed acyclic graph (PDAG) is a data structure that is used to represent a Boolean function. A Boolean function can be represented as a rooted, directed acyclic graph of the following form: * Leaves are labeled with (true), (false), or a Boolean variable. * Non-leaves are (logical and), (logical or) and (logical not). * - and -nodes have at least one child. * -nodes have exactly one child. Leaves labeled with represent the constant Boolean function which always evaluates to 1 (0). A leaf labeled with a Boolean variable is interpreted as the assignment , i.e. it represents the Boolean function which evaluates to 1 if and only if . The Boolean function represented by a -node is the one that evaluates to 1, if and only if the Boolean function of all its children evaluate to 1. Similarly, a -node represents the Boolean function that evaluates to 1, if and only if the Boolean function of at least one child evaluates to 1. Finally, a -node represents the complementary Boolean function its child, i.e. the one that evaluates to 1, if and only if the Boolean function of its child evaluates to 0. (Wikipedia).
