Before revision:  Main examples include enzymatic and post-translational modifications systems, where intermediates often are considered insignificant and neglected in a model . In each class , a mathematically simple canonical model  characterizes crucial dynamical properties, such as mono/ multistationarity and stability of steady states, of all models in the class.
After revision:  Main examples include enzymatic and post-translational modifications systems, where intermediates often are considered insignificant and neglected in a model , or they are not included because we are unaware of their existence. All possible models obtained from the core model are classified into a finite number of classes. Each class is defined by a mathematically simple canonical model characterizes crucial dynamical properties, such as mono/ multistationarity and stability of steady states, of all models in the class.