# Chain rule

From AMS Glossary

## chain rule

A basic inference rule used in most expert systems.

If

*A*implies*B*and*B*implies*C*, then it is also true that*A*implies*C*. For example, if the fact that it is July in Boston implies that the temperature is above freezing, and having the temperature above freezing implies that no precipitation will reach the ground as snow, it follows that it will not snow in Boston in July.