Explain Resource request and allocation graph (RRAG)

Deadlocks can be explained by a directed bipartite graph known as a Resource-Request-Allocation graph (RRAG).A graph G = (V,E) is known as bipartite if V can be decomposed into two disjoint sets V₁ and V₂ such that every edge in E joins a vertex in V₁ to a vertex in V₂. Suppose V₁ be a set of processes and V₂ be a set of resources. As the graph is directed we will consider:

a) An edge (R_j,P_i) that is an assignment edge to mean that resource R_j has been allocated to process P_i

b) An edge (P_i,R_j) that is called a request edge to mean that process P_i has requested resource R_j