Backend to the Xloopn screen editor

The continuing development of LOOPN, a language for object-oriented Petri nets, has resulted in Xloopn, an X-Windows graphical screen editor. The extension of Xloopn to allow communication with other Petri net tools is considered an important step. The integration of such a mechanism into the interface requires careful design. An examination of existing Petri net package interfaces has been undertaken to provide the necessary background to design the simulator tool interface elements. The mechanism to allow simulation of Petri nets created in Xloopn has been realised and has been integrated smoothly with the current interface.