The standard IEC 61499 claims to be a standard for a distributed control environment consisting of a set of heterogeneous control devices from different vendors. Previous work on the implementation of IEC 61499 pointed out ambiguities in the standard, resulting in different execution behavior of IEC 61499 elements on different control devices. One of the key deficiencies is the lack of a definition for execution models of the device, the resource, and the function blocks. This paper discusses different design and execution issues related to the aforementioned problems for IEC 61499 distributed automation and control systems.