The network to analyze must be undirected, otherwise there are no special constraints. The algorithm does not take edge weight into consideration in calculation of average path length.
Basic analysis tool, not particular for special disciplines or problems.
Boccaletti, S., Latora, V., Moreno, Y.,Chavez, M., Hwang, D.-U.(2006) Complex networks: Structure and dynamics. Physics Reports 424: 175-308.