OPQ , c M,M>C OPQ ) under UHV, and surface RAE oxidation states of the activated catalyst under wet feed (c M,e#C OPQ ).The relevance of these parameters reflects that the activity in alkane oxidation is governed by an interplay between the catalyst bulk and surface redox capacity (encoded by a b,$" * F , c M,9BC OPQ , c M,M>C OPQ , and c M,e#C OPQ ) with surface processes depending on the surface composition, in particular the adsorption strength (encoded by L M,$" D ) and the availability of surface vanadium or manganese (encoded by L M,$" OPQ , and L M,e#C OPQ ). Interestingly, the specific surface area, which is intuitively always associated with the activity of the catalysts, is not selected among the key primary features. The absolute difference between the RAE content on the fresh catalyst and the RAE content of the activated catalyst under wet reaction condi-tions (L M,$" OPQ -L M,e#C OPQ ) is identified by SISSO as one of the ingredients of the model. This points at the role of catalyst restructuring at the reaction conditions. The relevance of reversible oxygen uptake for catalyst activity is in line with the lattice oxygen pillar of oxidation catalysis. However, the more complex descriptor expression identified indicates that additional surface processes and the restructuring of the material play in concert with the materials' redox capacity to determine alkane conversion. In order to assess the importance of in situ characterization data for describing the activity in alkane oxidation, we have also performed the SISSO analysis by excluding the primary features obtained from NAP-XPS (Table and Fig. ). The minimum CV-RMSE significantly increases from 6.19 to 10.87% when the NAP-XPS information is not included. Moreover, the optimal complexity of the descriptor obtained without the in situ primary features is lower (q = 1) compared to that of eq. 2 (q = 3), which is reflected in the worse fit of the best model to the data set (Fig. ). In particular, the model obtained without the NAP-XPS data is unable to capture that the SmMnO3 becomes more active than MoVOx in the case of n-butane oxidation. These results indicate that the in situ information is crucial for modelling the reaction-dependent 8 9:;9<# . d and -4 d adapt to each reaction and temperature, while the descriptor 1 4 d assumes one single expression in all cases (see Table ). The 1 4 d values for a fixed material are different for each reaction because the parameters entering the expression are reaction-dependent. The catalysts are represented in B using the same convention as for Fig. .