Directed acyclic graphs are used to model the causal structure of a system.
``Causal discovery'' describes the problem of learning this structure from
data. When data is an aggregate from multiple sources (populations or
environments), global confounding obscures conditional independence properties
that drive many causal discovery algorithms. For this reason, existing causal
discovery algorithms are not suitable for the multiple-source setting. We
demonstrate that, if the confounding is of bounded cardinality (i.e. the data
comes from a limited number of sources), causal discovery can still be
achieved. The feasibility of this problem is governed by a trade-off between
the cardinality of the global confounder, the cardinalities of the observed
variables, and the sparsity of the causal structure.

使用有向无环图来建模系统的因果结构。在多个数据源（群体或环境）的数据聚合中，全局混淆模糊了许多因果发现算法中的条件独立性属性。因此，现有的因果发现算法不适用于多源设置。我们证明，如果混淆的基数有限（即数据来自有限数量的源），仍然可以实现因果发现。该问题的可行性取决于全局混淆因素的基数、观测变量的基数和因果结构的稀疏程度的权衡。