Restricted search of the space of source combinations. The heuristics described in Section ‘Details on the information sharing protocol - Restricting the search space’ is illustrated. In this example, we assume 4 subtypes A, B, C, and D. In each line a source combination is given, with the source combination in each being grouped. The most likely source combinations in each is colored in red. The arrows indicate how the spaces are traversed during the search process.