Probabilistic embedding into trees: definitions

A metric space is often represented as the pair (X,d). An example of metric spaces is (R, Lk), where Lk is the k-norm over R for given n, k ∈ Z≥1. We can represent a finite metric space (X, d) by a symmetric matrix S, of size nxn, where Si,j = d(i, j) and |X| = n. Metric spaces can be visualized using undirected graph G, where S is distance matrix for G. Conversely, given a graph G(V, E), we can represent it as a metric space (V, d), where d(i, j) is length of the shortest path between i, j ∈ V.