| Abstract: | Pearl's d -separation concept and the ensuing Markov property is applied to graphs which may have, between each two different vertices i and j , any subset of { i ← j , i → j , i ↔ j } as edges. The class of graphs so obtained is closed under marginalization. Furthermore, the approach permits a direct proof of this theorem: "The distribution of a multivariate normal random vector satisfying a system of linear simultaneous equations is Markov w.r.t. the path diagram of the linear system". |
