Any main model (or system) in 20-sim can be described as a composition of lower level submodels. These submodels in turn can be described as a composition of lower level submodels and so on. The lowest level consists of elementary submodels, that do not themselves consist of submodels.

The lowest model in the hierarchy is always an equation model.

You can view this in the Editor. When you click the Model tab at the left of the Editor, the Model Browser displays full model hierarchy: a tree-like structure showing all the submodels used in the model. If you open the example model Examples\Control\Standard Control\FluidLevelControl, the tree will look like:

The Model Browser at the left of the Editor shows the complete model hierarchy.

Tip

•	You can also select a submodel in the Graphical Editor and click Go Up or Go Down from the Model menu.

•	If a model is very large you may want to use the Go Back or Go Forward buttons in the Model menu to move back and forth between branches in the hierarchy.