Brief Introduction to Some Simple Classes: Some Definitions

From DSL

Here are the definitions of some terms that are used throughout the manual.

Partial Ordering: Partial ordering is a topological sort of a directed acyclic graph which can be viewed as an ordering of its vertices along a horizontal line so that all directed edges go from left to right.

Polytree: a network is a polytree if it is singly connected, namely, no more than one non-directed path exists between any two nodes.

Ancestor: Consider a node X in a directed acyclic graph. Any node Y on the directed path from root (those nodes without parents) to X is called an ancestor of X. If Y is an ancestor of X, then X is a descendant of Y.

Descendant: If node Y is an ancestor of node X, then node X is a descendant of node Y.

Temporal Order: In an Influence Diagram, decision nodes have to be linked in a time chain that defines the sequence in which the decisions will be made. Some decision nodes might also have informational predecessors that must be observed before the decision is made. Temporal order is defined as the sequence in which these observations/decisions are made.