Decoder::Slice Node1 Decoder::Slice   + addTob() + addTob() + getWords() Node2 std::vector< Decoder ::xTob >     Node2->Node1 +em_xtobs +tau_xtobs Node3 Decoder::xTob + word0 + word1   Node3->Node2 +elements Node4 std::vector< Decoder ::Tob >     Node4->Node1 +tobs Node5 Decoder::Tob + word0   Node5->Node4 +elements