IEC 61499: Back to the well proven practice of IEC 61131?

The IEC 61499 function block model was proposed as an extension of the widely accepted IEC 61131 function block diagram to address new challenges in the development of industrial automation software systems. Event driven execution is promoted as being one of the key features of this standard to achieve flexibility, interoperability and support for distribution. In this paper, it is claimed that 61499 fails in defining a coherent event handling model. Publications in the domain have also failed in addressing this problem adopting misperceptions and contradictions regarding the event driven nature of IEC 61499. These misperceptions and contradictions are discussed and an attempt is made to bring some light into this area so as to better exploit both 61131 and 61499.