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.

翻译：线性结构方程模型的观测特点可以用观测到的共变矩阵上的多数值限制来有效描述。 但是,这些多数值可能成倍大,因此对许多目的来说不切实际。在本文件中,我们为许多这些多数值限制提供了图形符号。这种符号的表达力在理论上和经验上都得到了研究。