We show that the marginal model for a discrete directed acyclic graph (DAG) with hidden variables is distributionally equivalent to another fully observable DAG model if and only if it does not induce any non-trivial inequality constraints.

翻译：我们表明,带有隐藏变量的离散定向单周期图(DAG)的边际模型在分布上等同于另一个完全可观测的DAG模型,条件是而且只有在它不引起任何非三角不平等限制的情况下。