What Is the Nested Set Model?

Nested model is a kind of structural equation model. If all the free parameters of model A are part of the same parameters in model B, it is said that model A is nested in model B. In the path map, the path map of model A can be obtained by removing some paths from the path map of model B. Let M be a model, not a virtual model or a saturated model, then the virtual model M. ^[1]