Decision rules
Encyclopedia
A set of decision rules is the verbal equivalent of a graphical decision tree
, which specifies class membership based on a hierarchical sequence of (contingent) decisions. Each rule in a set of decision rules therefore generally takes the form of a Horn clause
wherein class membership is implied by a conjunction of contingent observations.
where
is in general contingent on the choice of 
. Decision rules can be transcribed from the corresponding decision tree, or can be induced directly from observations.
Decision rules are commonly used in the medical field. For example, the Ottawa Ankle Rules guide obtaining radiographs for traumatic ankle pain.
Decision tree
A decision tree is a decision support tool that uses a tree-like graph or model of decisions and their possible consequences, including chance event outcomes, resource costs, and utility. It is one way to display an algorithm. Decision trees are commonly used in operations research, specifically...
, which specifies class membership based on a hierarchical sequence of (contingent) decisions. Each rule in a set of decision rules therefore generally takes the form of a Horn clause
Horn clause
In mathematical logic, a Horn clause is a clause with at most one positive literal. They are named after the logician Alfred Horn, who first pointed out the significance of such clauses in 1951...
wherein class membership is implied by a conjunction of contingent observations.
- IF
AND 
AND ... AND 
THEN CLASS = 
where
is in general contingent on the choice of . Decision rules can be transcribed from the corresponding decision tree, or can be induced directly from observations.Decision rules are commonly used in the medical field. For example, the Ottawa Ankle Rules guide obtaining radiographs for traumatic ankle pain.