Point patterns occurring on complex structures in space and space-time:   An alternative network approach
  This paper presents an alternative approach of analyzing possibly multitype point patterns in space and space-time that occur on network structures, and introduces several different graph-related intensity measures. The proposed formalism allows to control for processes on undirected, directional as well as partially directed network structures and is not restricted to linearity or circularity. 
Matthias Eckardt, Jorge Mateu
stat.AP physics.soc-ph