GXL (Graph eXchange Language) is designed to be a standard exchange format for graph-based tools. GXL is defined as an XML sublanguage,whic h offers support for exchanging instance graphs together with their appropriate schema information in a uniform format. Formally,GXL is based on typed,attributed,ordered directed graphs, which are extended by concepts to support representing hypergraphs and hierarchical graphs. Using this general graph model,GXL offers a versatile support for exchanging nearly all kinds of graphs.