A model is used to represent a set of structured data objects that include elements at defined positions. The model includes 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; 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. At least some of the distributions of the model differ such that different states of matching are indicated. Distributions of the model can indicate: dissimilarity between the structured data objects at defined positions; similarity between the structured data objects at defined positions; or similarity to a reference structure data object at defined positions.