  We present a dynamic data structure representing a graph G, which allows
addition and removal of edges from G and can determine the number of
appearances of a graph of a bounded size as an induced subgraph of G. The
queries are answered in constant time. When the data structure is used to
represent graphs from a class with bounded expansion (which includes planar
graphs and more generally all proper classes closed on topological minors, as
well as many other natural classes of graphs with bounded average degree), the
amortized time complexity of updates is polylogarithmic.
