For atoms, there are subcategories for options b) or c) to chose from (Table ). We will use the atom "[#6X3H2,#7X2H1;+0;A]" as an example of how decorators can be removed. For and'd decorators, we chose randomly with equal probability to either remove one (either '+0' or 'A') or all of the decorators. If one decorator is to be removed, that one is chosen at random from the list. In ChemicalEnvironments or'd decorators are split up into a base and list of sub-decorators. In our case we have two or'd decorators "#6X3H2" and "#7X2H1" which are split up into ('#6', ['X3', 'H2']) and ('#7', ['X2', 'H1']). There are six possible options for changing these decorators. In the most dramatic, all the or'd decorators are removed leaving us with the atom "[*;+0;A]." The simplest option is to remove just one sub-decorator (i.e. "X3"). A complete list of these options is described in Table . When choosing an option, we only consider those that are possible with the current decorators. For example, if we had already removed all sub-decorators Atom: all of one sub-decorator category "[#6X3H2,#7X2H1;+0;A:1]" → "[#6H2,#7H1;+0;A:1]" "[#6X3H2,#7X2H1;+0;A:1]" → "[#6X3,#7X2;+0;A:1]" Table . Categories for removing decorators as used in the Reducer. We will consider the SMIRKS "[#6X3H2,#7X2H1;+0;A:1]-,=;!@[#1:2]," and provide all possible changes to atom :1 or the bond. and now had the atom "[#6,#7;+0;A]," then categories referencing removing sub-decorators would not be considered on the next round for this atom. Otherwise, the category is chosen randomly with equal probability for each.