A new method is presented for applying multiple semantic constraints based on discrete relaxation. A separate graph is maintained for each constraint relation and is used in parallel to achieve a consistent labeling. This permits both local and global analysis without recourse to complete graphs. Here 'local' means with respect to particular constraint graph and thus actually includes global spatial relations on the features; e. g. , parallel edges on an object will be neighbors in the parallel constraint graph even though they are far apart in Euclidean space. Another result is a technique for handling occlusion by incorporating the use of spatially local feature sets in the relaxation-type updating method.