In relational DBMS, window functions have been widely used to facilitate data analytics. Surprisingly, while similar concepts have been employed for graph analytics, there has been no explicit notions of graph window analytic functions. In this paper, we formally introduce window queries for graph analytics. In such queries, for each vertex, the analysis is performed on a window of vertices defined based on the graph structure. In particular, we identify three instantiations, namely the unified window, the k-hop window and the topological window. We focus on processing the latter two window queries and develop two novel indices, Dense Block index (DBIndex) and Inheritance index (I-Index), to facilitate efficient processing of these two types of windows respectively.