The rule p itself also defines an ITS-like graph Υ(L, R, r • l -1 ) that captures the extended reaction center, i.e., all bonds that change together with necessary "context" prescribed by K. It is not difficult to verify that the ITS graph of the rule Υ(L, R, r • l -1 ) is (isomorphic to) a subgraph -but not necessarily an induced subgraph -of the ITS Υ(G, H, α). By construction Υ(L, R, r • l -1 ) contains the reaction center, i.e., all bonds that change during the reaction. A graphical summary is provided in Figure , and a more formal discussion based on is summarized as follows: