也称为(非参数)结构方程模型(SEMS)的结构因果模型(SCM)被广泛用于因果建模目的。特别是,也称为递归SEM的无循环SCMS,形成了一个研究的SCM的良好的子类,概括了因果贝叶斯网络来允许潜在混淆。在本文中,我们调查了更多普通环境中的SCM,允许存在潜在混杂器和周期。我们展示在存在周期中,无循环SCM的许多方便的性质通常不会持有:它们并不总是有解决方案;它们并不总是诱导独特的观察,介入和反事实分布;边缘化并不总是存在,如果存在边缘模型并不总是尊重潜在的投影;他们并不总是满足马尔可夫财产;他们的图表并不总是与他们的因果语义一致。我们证明,对于SCM一般,这些属性中的每一个都在某些可加工条件下保持。我们的工作概括了SCM的结果,迄今为止仅针对某些特殊情况所知的周期。我们介绍了将循环循环设置扩展到循环设置的简单SCM的类,同时保留了许多方便的无环SCM的性能。用本文,我们的目标是为SCM提供统计因果建模的一般理论的基础。
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动态系统广泛用于科学和工程,以模拟由多个交互组件组成的系统。通常,它们可以在意义上给出因果解释,因为它们不仅模拟了系统组件状态随时间的演变,而且描述了他们的进化如何受到动态的系统的外部干预的影响。我们介绍了结构动态因果模型(SDCMS)的正式框架,其将系统组件的因果语言作为模型的一部分来阐述。 SDCMS表示动态系统作为随机过程的集合,并指定了管理每个组件的动态的基本因果机制,作为任意顺序的随机微分方程的结构化系统。 SDCMS扩展了结构因果模型(SCM)的多功能因果建模框架,也称为结构方程模型(SEM),通过显式允许时间依赖。 SDCM可以被认为是SCM的随机过程版本,其中SCM的静态随机变量由动态随机过程及其衍生物代替。我们为SDCMS理论提供基础,(i)正式定义SDCMS,其解决方案,随机干预和图形表示; (ii)对初始条件的解决方案的存在性和独特性; (iii)随着时间的推移倾向于无穷大,讨论SDCMS平衡的条件下降; (iv)将SDCM的性质与平衡SCM的性质相关联。这封对应关系使人们能够在研究大类随机动力系统的因果语义时利用SCM的大量统计工具和发现方法。该理论用来自不同科学域的几个众所周知的示例进行说明。
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D分隔标准通过某些条件独立性检测到关节概率分布与定向无环图的兼容性。在这项工作中,我们通过引入因果模型的分类定义,D分隔的分类概念,并证明了D-Exaration Criterion的抽象版本,从而在分类概率理论的背景下研究了这个问题。这种方法有两个主要好处。首先,分类D分隔是基于拓扑连接的非常直观的标准。其次,我们的结果适用于度量理论概率(具有标准的鲍尔空间),因此提供了与局部和全球马尔可夫属性等效性具有因果关系兼容性的简洁证明。
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我们考虑代表代理模型的问题,该模型使用我们称之为CSTREES的阶段树模型的适当子类对离散数据编码离散数据的原因模型。我们表明,可以通过集合表达CSTREE编码的上下文专用信息。由于并非所有阶段树模型都承认此属性,CSTREES是一个子类,可提供特定于上下文的因果信息的透明,直观和紧凑的表示。我们证明了CSTREEES承认全球性马尔可夫属性,它产生了模型等价的图形标准,概括了Verma和珍珠的DAG模型。这些结果延伸到一般介入模型设置,使CSTREES第一族的上下文专用模型允许介入模型等价的特征。我们还为CSTREE的最大似然估计器提供了一种封闭式公式,并使用它来表示贝叶斯信息标准是该模型类的本地一致的分数函数。在模拟和实际数据上分析了CSTHEELE的性能,在那里我们看到与CSTREELE而不是一般上演树的建模不会导致预测精度的显着损失,同时提供了特定于上下文的因果信息的DAG表示。
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在观察性研究中,经常遇到有关存在或缺乏因果边缘和路径的因果背景知识。由于背景知识而导致的马尔可夫等效dag的子类共享的指向边缘和链接可以由因果关系最大部分定向的无循环图(MPDAG)表示。在本文中,我们首先提供了因果MPDAG的声音和完整的图形表征,并提供了因果MPDAG的最小表示。然后,我们介绍了一种名为Direct Causal子句(DCC)的新颖表示,以统一形式表示所有类型的因果背景知识。使用DCC,我们研究因果背景知识的一致性和等效性,并表明任何因果背景知识集都可以等效地分解为因果MPDAG,以及最小的残留DCC。还提供了多项式时间算法,以检查一致性,等效性并找到分解的MPDAG和残留DCC。最后,有了因果背景知识,我们证明了一个足够且必要的条件来识别因果关系,并且出人意料地发现因果效应的可识别性仅取决于分解的MPDAG。我们还开发了局部IDA型算法,以估计无法识别效应的可能值。模拟表明因果背景知识可以显着提高因果影响的识别性。
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研究了与隐藏变量有关的非循环图(DAG)相关的因果模型中因果效应的识别理论。然而,由于估计它们输出的识别功能的复杂性,因此未耗尽相应的算法。在这项工作中,我们弥合了识别和估算涉及单一治疗和单一结果的人口水平因果效应之间的差距。我们派生了基于功能的估计,在大类隐藏变量DAG中表现出对所识别的效果的双重稳健性,其中治疗满足简单的图形标准;该类包括模型,产生调整和前门功能作为特殊情况。我们还提供必要的和充分条件,其中隐藏变量DAG的统计模型是非分子饱和的,并且意味着对观察到的数据分布没有平等约束。此外,我们推导了一类重要的隐藏变量DAG,这意味着观察到观察到的数据分布等同于完全观察到的DAG等同于(最高的相等约束)。在这些DAG类中,我们推出了实现兴趣目标的半导体效率界限的估计估计值,该估计是治疗满足我们的图形标准的感兴趣的目标。最后,我们提供了一种完整的识别算法,可直接产生基于权重的估计策略,以了解隐藏可变因果模型中的任何可识别效果。
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我们提出了普遍因果关系,这是一个基于类别理论的总体框架,该框架定义了基于因果推理的普遍特性,该属性独立于所使用的基本代表性形式主义。更正式的是,普遍的因果模型被定义为由对象和形态组成的类别,它们代表因果影响,以及进行干预措施(实验)和评估其结果(观察)的结构。函子在类别之间的映射和自然变换映射在相同两个类别的一对函子之间。我们框架中的抽象因果图是使用类别理论的通用构造构建的,包括抽象因果图的限制或共限制,或更普遍的KAN扩展。我们提出了普遍因果推断的两个基本结果。第一个结果称为普遍因果定理(UCT),与图的通用性有关,这些结果被视为函数映射对象和关系从抽象因果图的索引类别到一个实际因果模型,其节点由随机变量标记为实际因果模型和边缘代表功能或概率关系。 UCT指出,任何因果推论都可以以规范的方式表示为代表对象的抽象因果图的共同限制。 UCT取决于滑轮理论的基本结果。第二个结果是因果繁殖特性(CRP),指出对象x对另一个对象y的任何因果影响都可以表示为两个抽象因果图之间的自然转化。 CRP来自Yoneda引理,这是类别理论中最深层的结果之一。 CRP属性类似于复制元素希尔伯特空间中的繁殖属性,该元素是机器学习中内核方法的基础。
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常用图是表示和可视化因果关系的。对于少量变量,这种方法提供了简洁和清晰的方案的视图。随着下属的变量数量增加,图形方法可能变得不切实际,并且表示的清晰度丢失。变量的聚类是减少因果图大小的自然方式,但如果任意实施,可能会错误地改变因果关系的基本属性。我们定义了一种特定类型的群集,称为Transit Cluster,保证在某些条件下保留因果效应的可识别性属性。我们提供了一种用于在给定图中查找所有传输群集的声音和完整的算法,并演示集群如何简化因果效应的识别。我们还研究了逆问题,其中一个人以群集的图形开始,寻找扩展图,其中因果效应的可识别性属性保持不变。我们表明这种结构稳健性与过境集群密切相关。
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大多数现代的潜在变量和概率生成模型,例如变异自动编码器(VAE),即使有无限的数据也无法解决,这些模型也无法解决。此类模型的最新应用表明需要强烈可识别的模型,其中观察结果与唯一的潜在代码相对应。在维持灵活性的同时,取得了进展,最著名的是IVAE(Arxiv:1907.04809 [stat.ml]),该模型排除了许多(但不是全部 - 不确定)。我们构建了一个完整的理论框架,用于分析潜在变量模型的不确定性,并根据生成器函数的属性和潜在变量先验分布精确表征它们。为了说明,我们应用框架以更好地了解最近的可识别性结果的结构。然后,我们研究如何指定强烈识别的潜在变量模型,并构建两个这样的模型。一种是对ivae的直接修饰。另一个想法从最佳运输和导致新颖的模型和连接到最近的工作。
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In this review, we discuss approaches for learning causal structure from data, also called causal discovery. In particular, we focus on approaches for learning directed acyclic graphs (DAGs) and various generalizations which allow for some variables to be unobserved in the available data. We devote special attention to two fundamental combinatorial aspects of causal structure learning. First, we discuss the structure of the search space over causal graphs. Second, we discuss the structure of equivalence classes over causal graphs, i.e., sets of graphs which represent what can be learned from observational data alone, and how these equivalence classes can be refined by adding interventional data.
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We study experiment design for unique identification of the causal graph of a system where the graph may contain cycles. The presence of cycles in the structure introduces major challenges for experiment design as, unlike acyclic graphs, learning the skeleton of causal graphs with cycles may not be possible from merely the observational distribution. Furthermore, intervening on a variable in such graphs does not necessarily lead to orienting all the edges incident to it. In this paper, we propose an experiment design approach that can learn both cyclic and acyclic graphs and hence, unifies the task of experiment design for both types of graphs. We provide a lower bound on the number of experiments required to guarantee the unique identification of the causal graph in the worst case, showing that the proposed approach is order-optimal in terms of the number of experiments up to an additive logarithmic term. Moreover, we extend our result to the setting where the size of each experiment is bounded by a constant. For this case, we show that our approach is optimal in terms of the size of the largest experiment required for uniquely identifying the causal graph in the worst case.
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We propose a layered hierarchical architecture called UCLA (Universal Causality Layered Architecture), which combines multiple levels of categorical abstraction for causal inference. At the top-most level, causal interventions are modeled combinatorially using a simplicial category of ordinal numbers. At the second layer, causal models are defined by a graph-type category. The non-random ``surgical" operations on causal structures, such as edge deletion, are captured using degeneracy and face operators from the simplicial layer above. The third categorical abstraction layer corresponds to the data layer in causal inference. The fourth homotopy layer comprises of additional structure imposed on the instance layer above, such as a topological space, which enables evaluating causal models on datasets. Functors map between every pair of layers in UCLA. Each functor between layers is characterized by a universal arrow, which defines an isomorphism between every pair of categorical layers. These universal arrows define universal elements and representations through the Yoneda Lemma, and in turn lead to a new category of elements based on a construction introduced by Grothendieck. Causal inference between each pair of layers is defined as a lifting problem, a commutative diagram whose objects are categories, and whose morphisms are functors that are characterized as different types of fibrations. We illustrate the UCLA architecture using a range of examples, including integer-valued multisets that represent a non-graphical framework for conditional independence, and causal models based on graphs and string diagrams using symmetric monoidal categories. We define causal effect in terms of the homotopy colimit of the nerve of the category of elements.
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Variational autoencoders and Helmholtz machines use a recognition network (encoder) to approximate the posterior distribution of a generative model (decoder). In this paper we study the necessary and sufficient properties of a recognition network so that it can model the true posterior distribution exactly. These results are derived in the general context of probabilistic graphical modelling / Bayesian networks, for which the network represents a set of conditional independence statements. We derive both global conditions, in terms of d-separation, and local conditions for the recognition network to have the desired qualities. It turns out that for the local conditions the property perfectness (for every node, all parents are joined) plays an important role.
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Learning causal structure from observational data often assumes that we observe independent and identically distributed (i.\,i.\,d) data. The traditional approach aims to find a graphical representation that encodes the same set of conditional independence relationships as those present in the observed distribution. It is known that under i.\,i.\,d assumption, even with infinite data, there is a limit to how fine-grained a causal structure we can identify. To overcome this limitation, recent work has explored using data originating from different, related environments to learn richer causal structure. These approaches implicitly rely on the independent causal mechanisms (ICM) principle, which postulates that the mechanism giving rise to an effect given its causes and the mechanism which generates the causes do not inform or influence each other. Thus, components of the causal model can independently change from environment to environment. Despite its wide application in machine learning and causal inference, there is a lack of statistical formalization of the ICM principle and how it enables identification of richer causal structures from grouped data. Here we present new causal de Finetti theorems which offer a first statistical formalization of ICM principle and show how causal structure identification is possible from exchangeable data. Our work provides theoretical justification for a broad range of techniques leveraging multi-environment data to learn causal structure.
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动态系统中的完美适应性是一个或多个变量具有对外部刺激的持续变化的初始短暂响应的现象,但随着系统收敛到平衡,其原始值还原为原始值。借助因果有序算法,可以构建代表变量之间的因果关系和平衡分布中条件独立性之间的因果关系的图形表示。我们应用这些工具来制定足够的图形条件,以识别一组一阶微分方程的完美适应。此外,我们提供了足够的条件来测试实验平衡数据中完美适应的情况。我们将此方法应用于蛋白质信号通路的简单模型,并在模拟和使用现实世界中的蛋白质表达数据中测试其预测。我们证明,完美的适应会导致因果发现算法输出中边缘的误导方向。
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概括指向的最大祖先图形,我们介绍了一类图形模型,用于表示与未观察的变量的多变量时间序列的多变量时间序列的多变量的多种定样和定期分配时间步骤中的时间滞后特定因果关系和独立性。我们完全阐述了这些图表,并表明他们需要超出以前在文献中被考虑的那些的限制。这允许在没有强加的额外假设的情况下更强的因果推断。在指向部分祖先图的概括中,我们进一步介绍了新颖类型的图表的马尔可夫等同类的图形表示,并显示这些比当前最先进的因果发现算法学习的更具信息量。我们还通过增加观察时间步骤的数量来分析所获得的附加信息。
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本文介绍了在结构因果模型(SCM)的一般空间上定义的一系列拓扑结构,介绍了因果推断的拓扑学习 - 理论观点。作为框架的说明,我们证明了拓扑因果层次结构定理,表明只有在微薄的SCM集中就可以实现了无实体的假设因果推断。由于弱拓扑结构和统计上可验证假设的开放集之间的已知对应关系,我们的结果表明,原则上的归纳假设足以许可有效的因果推论是统计上无可核实的。类似于无午餐定理的统计推断,目前的结果阐明了因果推断的实质性假设的必然性。我们拓扑方法的额外好处是它很容易容纳具有无限变量的SCM。我们终于建议该框架对探索和评估替代因果归纳的积极项目有所帮助。
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我们研究了在存在潜在变量存在下从数据重建因果图形模型的问题。感兴趣的主要问题是在潜在变量上恢复因果结构,同时允许一般,可能在变量之间的非线性依赖性。在许多实际问题中,原始观测之间的依赖性(例如,图像中的像素)的依赖性比某些高级潜在特征(例如概念或对象)之间的依赖性要小得多,这是感兴趣的设置。我们提供潜在表示和潜在潜在因果模型的条件可通过减少到混合甲骨文来识别。这些结果突出了学习混合模型的顺序的良好研究问题与观察到和解开的基础结构的问题之间的富裕问题之间的有趣连接。证明是建设性的,并导致几种算法用于明确重建全图形模型。我们讨论高效算法并提供说明实践中算法的实验。
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有条件的独立性已被广泛用于AI,因果推理,机器学习和统计数据。我们介绍分类生物,这是一种代数结构,用于表征条件独立性的普遍特性。分类物被定义为两个类别的混合体:一个编码由对象和箭头定义的预订的晶格结构;第二个二个参数化涉及定义​​条件独立性结构的三角体对象和形态,桥梁形态提供了二进制和三元结构之间的接口。我们使用公理集的三个众所周知的示例来说明分类生物:绘画,整数价值多组和分离型。 FOUNDOROIDS将一个分类型映射到另一个分类,从而保留了由共同域中所有三种类型的箭头定义的关系。我们描述了跨官能素的自然转化,该函数是跨常规物体和三角形对象的自然变化,以构建条件独立性的通用表示。我们使用分类器之间的辅助和单核,以抽象地表征条件独立性的图形和非图形表示的忠诚。
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Linear structural causal models (SCMs)-- in which each observed variable is generated by a subset of the other observed variables as well as a subset of the exogenous sources-- are pervasive in causal inference and casual discovery. However, for the task of causal discovery, existing work almost exclusively focus on the submodel where each observed variable is associated with a distinct source with non-zero variance. This results in the restriction that no observed variable can deterministically depend on other observed variables or latent confounders. In this paper, we extend the results on structure learning by focusing on a subclass of linear SCMs which do not have this property, i.e., models in which observed variables can be causally affected by any subset of the sources, and are allowed to be a deterministic function of other observed variables or latent confounders. This allows for a more realistic modeling of influence or information propagation in systems. We focus on the task of causal discovery form observational data generated from a member of this subclass. We derive a set of necessary and sufficient conditions for unique identifiability of the causal structure. To the best of our knowledge, this is the first work that gives identifiability results for causal discovery under both latent confounding and deterministic relationships. Further, we propose an algorithm for recovering the underlying causal structure when the aforementioned conditions are satisfied. We validate our theoretical results both on synthetic and real datasets.
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