18. The computer-usable storage medium of claim 17 , wherein the computer-readable program code embodied therein causes a computer system to perform the method, and wherein the creating of the forward-in-time graph further comprises: creating the forward-in-time graph that has path lengths from the particular document to other documents that are less than or equal to a user specified maximum path length value; and creating a reverse-in-time graph based on the forward-in-time graph.
18. The computer-usable storage medium of claim 17 , wherein the computer-readable program code embodied therein causes a computer system to perform the method, and wherein the creating of the forward-in-time graph further comprises: creating the forward-in-time graph that has path lengths from the particular document to other documents that are less than or equal to a user specified maximum path length value; and creating a reverse-in-time graph based on the forward-in-time graph. 19. The computer-usable storage medium of claim 18 , wherein the computer-readable program code embodied therein causes a computer system to perform the method, and wherein the determining of the subsets of the documents further comprises: creating an initial matrix of probabilities based on the reverse-in-time graph; multiplying the initial matrix of probabilities by itself, to create a plurality of matrixes wherein each matrix is considered a generation, until a matrix of probabilities is achieved, wherein the values from the matrix of probabilities is similar to the values from the previous generation matrix; and determining the subset from the matrix of probabilities.