  An instance of the maximum mixed graph orientation problem consists of a
mixed graph and a collection of source-target vertex pairs. The objective is to
orient the undirected edges of the graph so as to maximize the number of pairs
that admit a directed source-target path. This problem has recently arisen in
the study of biological networks, and it also has applications in communication
networks.
  In this paper, we identify an interesting local-to-global orientation
property. This property enables us to modify the best known algorithms for
maximum mixed graph orientation and some of its special structured instances,
due to Elberfeld et al. (CPM '11), and obtain improved approximation ratios. We
further proceed by developing an algorithm that achieves an even better
approximation guarantee for the general setting of the problem. Finally, we
study several well-motivated variants of this orientation problem.
