An MxModel may contain: lists of MxMatrices, MxAlgebras, MxConstraints, no more than one MxData object, and an objective function. There are also slots in the MxModel that contain a list of optimization options and a list that contains output from the most recent optimization run. We note here that MxModels can also contain a list of other MxModels. This allows one to create a hierarchical tree of MxModels which is subsumed within a root MxModel container. A hierarchical tree of child and parent MxModels provides a new way of thinking about constructing SEM models that is surprisingly powerful.
