Optimal identification of sets of edges using 2-factors

The problem of identifying a single arbitrary edge in a graph using edge-identifying codes was recently considered by Foucaud et al. (in press) [4]. In this paper, we focus on locating more than one edge. First, we classify the graphs in which this is possible. Furthermore, for such graphs, we give a simple characterization of edge-identifying codes. Using the characterization, we give various lower and upper bounds for edge-identifying codes in terms of the order and size of a graph. In particular, codes with the minimum cardinality are obtained with the aid of 2-factors. In addition, we consider how the cardinality of the smallest edge-identifying codes behaves when an edge is added to a graph.