A graph can be partitioned into nested subgraphs. Subgraphs can be defined only statically, i.e. in the graph specification. In the GDL specification, subgraphs should be specified in such a manner so that the user can identify subgraphs and summary nodes can thus make use of all the operations that work on subgraphs.
A subgraph is selected by clicking on one of its nodes. The interactive folding, boxing, clustering and wrapping operations allow more than one subgraphto be selected at the same time. Instructions appearing in the message window guide the user through the selection procedure.