1. A computer-implemented method comprising: receiving the plurality of source hierarchical schemas, each source hierarchical schema being stored as a computer-readable document in computer-readable memory; processing, using a computer, the source hierarchical schemas to generate a merged graph, the merged graph comprising a plurality of merged nodes, each merged node being provided based on one or more nodes from at least two of the source hierarchical schemas; and determining, using the computer, that the merged graph includes one or more conflicts and, in response, resolving each conflict of the one or more conflicts to generate a computed-transitive-edge-free, conflict-free merged graph as a unified data model (UDM), wherein resolving comprises splitting one or more merged nodes into respective sub-sets of merged nodes.