11. A system comprising one or more computers and one or more storage devices storing instructions that when executed by the one or more computers to perform operations comprising: receiving an input comprising a plurality of features of a resource, wherein each feature is a value of a respective attribute of the resource; generating an alternative representation of the features of the resource, comprising: generating a respective numeric representation of each of 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 of the features of the resource; and providing the alternative representation of the features of the resource as input to a neural network classifier for classification of the resource as belonging to one or more categories of a plurality of categories.
17. The system of claim 11 , wherein the plurality of categories includes a respective category for each of a plurality of types of search engine spam.