In some cases (e.g. furan synthesis) that could not be predicted for the unsubstituted ring system (Figure ), we have previously observed that a disconnection could be predicted from the substituted ring system (Figure , substrates 1 and 2). In such cases, it is a problem of template availability and the underlying dataset on which the model is trained. The template must be able to describe the changing atoms and bonds in the reaction, and therefore be specific to the reaction from which it was extracted in terms of the local molecular environment. Yet the template must also be able to be generally applied to a variety of compounds containing the same molecular environment from which the template was first extracted. Finally, the network is trained on the product of the reactions, and the corresponding templates as labels. Therefore, for the network to 'learn' in which context a given template can be applied, there must be a sufficient number of diverse examples containing the same local molecular environment to which the template has a substructure match. In this way, the network is better able to generalize to which compound a given template can be applied, and may explain why compounds, and by association templates that occur frequently within the dataset are better 'understood' by the network.