1. A method performed by one or more computers, the method comprising: receiving an input comprising a plurality of features of a resource, wherein each of the features is of a different feature type; generating an alternative representation of the features of the resource, comprising: generating a respective numeric representation of each the features by processing each of the features using a respective embedding function, wherein each of the embedding functions is specific to features of a respective feature type, and processing the respective numeric representations through one or more neural network layers to generate the alternative representation; and providing the alternative representation of the features of the resource as input to a neural network classifier for classification of a relevance of a plurality of concept terms to the resource.