Surface) models require the on-the-fly ab initio energy evaluation of the species S involved along the reaction paths . As such, they are only amenable to chemical spaces of the order of 10 2 intermediates. Alternatively, rule-based CRN models employ templates to define the attainable chemical space via a list of possible transformations . These algorithms can decouple the network generation from the energy evaluation. Therefore, they lead to larger networks compared to CRN-PES, including multiple paths which could contribute to the catalytic activity or expand rare events responsible for catalyst degradation, thus getting closer than CRN-PES to achieve the completeness of the chemical space. However, the combinatorial explosion of the chemical space requires strategies to reduce the CRN complexity and/or substitute DFT with fast energy estimators.