fig given layer sourc destin attach end fig edg param layer layer look fig node param edg edg attach set port layer layer fig edg edg object model element edg owner edg sourc port fig object sourc model element comment edg sourc comment edg model element sourc sourc model uml helper sourc model element fig node sourc node node present layer sourc sourc node fig node sourc set sourc port edg sourc node edg dest port fig object dest model element comment edg dest comment edg model element destin dest model uml helper destin edg owner set dest port edg node present layer dest edg sourc port fig edg dest port fig illeg state except edg type edg creat sourc destin port 