The model definition commands build up a complete model as a hierarchy of systems, equations, operators, and functions based on the available regions and fields. Each of the model definition commands creates a new TCL commmand, so you will often see TCL code similar to
set myModel [model ... $myModel -modelCmdIn this fragment, the TCL variable myModel is used to store the name of the command created by the model command. The syntax $myModel substitutes the string stored by the TCL variable myModel (i.e. the name of the new command) before interpreting the second line and running the new command.
The commands for the components of a model definition are described below in a bottom-up fashion.