  This paper presents a sound and completecalculus for causal relevance, based
onPearl's functional models semantics.The calculus consists of axioms and
rulesof inference for reasoning about causalrelevance relationships.We extend
the set of known axioms for causalrelevance with three new axioms, andintroduce
two new rules of inference forreasoning about specific subclasses
ofmodels.These subclasses give a more refinedcharacterization of causal models
than the one given in Halpern's axiomatizationof counterfactual
reasoning.Finally, we show how the calculus for causalrelevance can be used in
the task ofidentifying causal structure from non-observational data.
