Execution Models for the IEC 61499 elements Composite Function Block and Subapplication

The semantic loopholes of the standard IEC 61499 have been pointed out in different recent publications with focus on some details. This paper investigates especially on the execution models for composite function blocks and subapplications. Of course this is closely related to the execution of basic function blocks and function block networks. Therefore, this work is based on general assumptions about these parts. The different possibilities concerning composite function blocks are described in detail and explained in a case study of a very simple example function block. For the sake of describing the relation to current runtime environments, three current implementations are used in the case study.