These approaches include metadata extraction (Cao et al., 2005), expert profile building (Craswell, 2001, Fu et al., 2007, data fusion (Maconald and Ounis, 2006), query expansion (Macdonald and Ounis, 2007), hierarchical language model (Petkova and Croft, 2006), and formal model generation (Balog et al., 2006;Fang et al., 2006).
all of them conduct expert search with what we call a coarse-grained approach.