We introduce new data structures for answering connectivity queries in graphs subject to batched vertex failures. Our deterministic structure processes a batch of d ≤ d failed vertices inÕ(d 3 ) time and thereafter answers connectivity queries in O(d) time. It occupies space O(d m log n). We develop a randomized Monte Carlo version of our data structure with update timeÕ(d 2 ), query time O(d), and spaceÕ(m) for any d . This is the first connectivity oracle for general graphs that can efficiently deal with an unbounded number of vertex failures.Our data structures are based on a new decomposition theorem for an undirected graph G = (V, E), which is of independent interest. It states that for any terminal set U ⊆ V we can remove a set B of |U |/(s − 2) vertices such that the remaining graph contains a Steiner forest for U − B with maximum degree s.
IntroductionThe dynamic subgraph model [19,21,36,39,37,42,65] is a constrained dynamic graph model. Rather than allow the graph to evolve in completely arbitrary ways (via an unbounded sequence of edge insertions and deletions), there is assumed to be a fixed ideal graph G = (V, E) that can be preprocessed in advance. The ideal graph is susceptible only to the failure of edges/vertices and their subsequent recovery, possibly with a bound d on the number of failures at one time. Queries naturally answer questions about the current failure-free subgraph. This model is useful because it more accurately represents the behavior of many real-world networks: changes to the underlying topology are relatively rare but transient failures very common. More importantly, this model offers the algorithm designer the freedom to explore exotic graph rep-