Operators over generalized nets

The idea of defining operators over the set of generalized nets dates back to 1982 and now they comprise an important area of research. An operator's function is to assigns to a given generalized net a new generalized net that possess some desired properties. Six types of operators have been defined over the generalized nets:


 * Global ($\mathcal{G}$) operators,
 * Local ($\mathcal{P}$) operators,
 * Hierarchical ($\mathcal{H}$) operators,
 * Reducing $(\mathcal{R}$) operators,
 * Extending ($\mathcal{O}$) operators,
 * Dynamical ($\mathcal{D}$) operators.