1. A method comprising: specifying a model that (i) represents a set of structured data objects that include elements at particular positions, and (ii) comprises distributions of vectors, each distribution corresponding to particular positions in the respective structured data objects, each of the vectors comprising values for the particular positions, at least some distributions indicating dissimilarity at particular positions of the structured data objects; and comparing a given set of structured data objects to the model to determine a likelihood that the given set is represented by the model.