1. A system for decomposing a digital image, comprising: a digital image stored as a word-graph comprising words and visualized features, and zone hypotheses that group one or more of the words; and an image decomposer, comprising: a zone modeler expressing causal dependencies of the zone hypotheses through a learned generative zone model to which costs and constraints are assigned; and a zone inference engine inferring an optimal set of the zone hypotheses, which are non-overlapping, through a heuristic search of the costs and constraints.