The observational characteristics of a linear structural equation model can be effectively described by polynomial constraints on the observed covariance matrix. However, these polynomials can be exponentially large, making them impractical for many purposes. In this paper, we present a graphical notation for many of these polynomial constraints. The expressive power of this notation is investigated both theoretically and empirically.

中文翻译：

---

线性结构方程模型的代数约束的图形表示

线性结构方程模型的观测特征可以通过观测协方差矩阵的多项式约束来有效地描述。然而，这些多项式可能是指数级的，这使得它们对于许多用途来说是不切实际的。在本文中，我们提出了许多这些多项式约束的图形表示法。这种符号的表达能力在理论上和经验上都得到了研究。