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3.2 Net Graph Problem with a Bounded Number of Nets (bounded_n_nets_graph) The class Net Graph Problem with a Bounded Number of Nets is a direct descendant of the class General Net Graph Problem with the specialization that graphs in this problem class have a bounded number of nets. The number of terminals in a net remains arbitrary. The number of nets can be set in the class and is initially bounded to 1. 3.3 Net Graph Problem with a Bounded Number of Terminals per Net (bounded_netsize_graph) The class Net Graph Problem with a Bounded Number of Terminals per Net is also a direct descendant of the class General Net Graph Problem. The graphs in this problem class have a bounded number of terminals per net; the number of nets remains arbitrary. Initially, the number of terminals per net is bounded to 2, but can be set to an arbitrary value. 3.4 Menger Problem (menger) ë ì í ì í ë Let be an undirected planar graph with two specified terminals and . The Menger Problem is to find a maximum number of internally vertex/edge–disjoint paths between and in . Without loss of generality, here, the embedding of is enforced such that is situated on the outer face of . ë í ë The class Menger Problem is modeled as a direct descendant of the class Net Graph Problem with a Bounded Number of Nets and of the class Net Graph Problem with a Bounded Number of Terminals per Net. The graphs of the class Menger Problem have one net with two terminals and . The –terminal has to be on the outer face. ì í í 3.5 Okamura–Seymour Problem (okamura_seymour_graph) ëînï°ð åPñLò ì©ø íø ùûú1üGúJý ó?îõô¦ô/ì¦Ù å íöÙ÷ åæææ©å ô/ì/ç å íçh÷¦÷ ë ï°ð åPñJþ ô/ìÙ å íyÙÏ÷ þÿæææþ ô/ì/ç å íçh÷ ò ÙÏåæææ©å bç Let be an undirected planar graph with a set of nets . The terminal nodes , , , are all on the outer face of . Additionally, the so called evenness condition is fulfilled, that is the extended graph is Eulerian. The Okamura–Seymour Problem is to decide whether there are pairwise edge–disjoint paths , so that connects with for , and if so, to determine such a set of paths. ø ì©ø ílø ü:îsù åæææ©å ý The class Okamura–Seymour Problem is modeled as a descendant of the class Net Graph Problem with a Bounded Number of Terminals per Net. The graphs of this problem class contain an arbitrary number of nets with two terminals each. Both of the terminals of each net are on the outer face, each terminal has degree 1 and all other nodes have even degree. 17