arXiv:2608.17634cs.AIcs.PL2026-08

揭示了图手术与因果干预算子在确定性因果模型中的精确对应关系。

Graph Surgery and the Do-Operator: A Precise Correspondence for Acyclic Structural Causal Models

  • 通过依赖层级对比,证明图手术与do算子等价
  • 干预后变量仅受其实际因果祖先影响
  • 结果已在Lean 4中形式化验证,适合因果推理研究者

do算子的图形化操作是删除目标节点的入边,功能化操作则是用常数替换其机制。二者看似等价,实则返回不同对象:一为图结构并仅记录目标节点,一为机制并保留干预值。本文针对具有有限内生变量的确定性无环结构因果模型,建立依赖层级的精确比较。若Graph(F)提取机制族F的依赖关系,则主定理为Graph(F^ι)=Surg(Graph(F),T_ι),即替换目标机制恰好移除对应依赖。对于模型M=(G,F),当且仅当图G精确记录了机制族的依赖关系时,该等式对所有干预成立。进一步定义干预后模型,刻画其运行机制,说明序列干预的组合方式,并证明结果仅依赖于实际因果祖先的干预。所有核心结论均在配套Lean 4形式化开发中机器验证。

原文摘要 · Abstract (English)

The $\operatorname{do}$-operator is described graphically by deleting arrows into its targets and functionally by replacing their mechanisms with constants. To call these operations equivalent is not yet a mathematical statement: one returns a graph and remembers only the targets, whereas the other returns mechanisms and also remembers the imposed values. We make a dependency-level comparison precise for deterministic acyclic structural causal models with finitely many endogenous variables. If $\operatorname{Graph}(F)$ extracts the dependencies of a mechanism family $F$, our main theorem is $\operatorname{Graph}(F^ι)=\operatorname{Surg}(\operatorname{Graph}(F),T_ι)$. Thus replacing target mechanisms removes exactly the dependencies removed by graph surgery. For a model $M=(G,F)$ whose graph may contain unused arrows, we characterize when the same equality holds with $G$ in place of $\operatorname{Graph}(F)$; it holds for every intervention exactly when $G$ records the dependencies of $F$ exactly. We then define the intervened model, characterize its run, show how sequential interventions combine, and prove that an outcome depends only on interventions at its actual dependency ancestors. All principal results are machine-checked in an accompanying Lean 4 development.

因果推理结构因果模型形式化验证

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