Loosely coupled systems are benefited from higher changeability. They are less rigid and more flexible because they are loose but still connected as they are coupled. On the other hand, they could behave unpredictably in the course of sudden change. While many studies and industrial practices are trying to make PLC-based control and automation software more loosely coupled, this paper aims to bring the attention of subject matter experts to the fact that making PLCbased control and automation software too loosely coupled could demolish the main characteristic of these systems, which relies on their predictability and reliability.

Although generally speaking, modularisation is not a new topic in the software industry, industrial control and automation software systems based on industrial computers recently received greater attention from academia and industry due to the impact of modularisation on managing software complexities, particularly changeability. While there is a direct correlation between coupling and modularisation and their impact on software changeability and reusability, not all modularisation techniques could bring higher changeability unless it is performed in the direction of changeability. How to modularise in the direction of changeability is the core topic of this paper.

The history of the software industry has shown and proved that coupling and cohesion are a never-ending story in this industry. Quantifying the quality of software systems by measuring the strength of coupling and cohesion and considering it a rule that good software has low coupling between its parts and high cohesion within each part, is currently widely accepted. Every paradigm shift, new technology, language, etc. that didn`t consider this fact had to sooner or later leave this industry. It is, therefore, crucial to study and consider this fact in every new topic in the software industry. Surprisingly neither the IEC 61499 nor IEC 61131 communities have yet conducted a deep study to evaluate what coupling and cohesion really mean for Industrial Control and Automation Applications. We hope this paper will manage to fulfill this considerable gap, if not fully at least partially.

Coupling could be an arbitrary property to Industrial Automation and Control Systems (ICAS) with a significant impact on complexity. Different software design approaches may result in coupling between software modules that either increase or decrease the overall system complexity. This paper proposes using the Cynefin Framework to guide the software design patterns used during the high-level design of software architecture, with the intent of reducing components coupling and overall system complexity.

Applying service-oriented concepts in industrial control and automation systems requires developing new architectural concepts to make it more adaptable to this context. In the scope of service-oriented systems one of the main challenges is defining the right granularity for every service in the system. This paper presents a systematic classification of methods to decompose the services. Identifying and using the correct granularity for each service is expected to lead to higher system flexibility, scalability, and in general to improving service deployment and maintenance. To find the best granularity for a service several approaches have been proposed, some of which are based on modeling and others based on service quality analysis. The approach we propose is based on modeling.

Plug & Produce is an important part of the 4thindustrial revolution (I4.0) that focuses on product development and production scenarios, demanding rapid adaptation to customer needs, with minimum effort, and no business interruption. Achieving this requires the use of flexible and agile automation systems. Microservices Architecture can be an opportunity to bring such flexibility and agility to industrial automation systems. Since Microservices Architecture is a new paradigm in service-oriented systems, an in-depth analysis from the industrial automation perspective is necessary in order to figure out why and how this new architecture could be helpful to build flexible automation systems. In this paper we first clearly describe and characterize the Microservices Architecture. We next discuss an existing paradox in microservice granularity, and suggest an approach to solve the mentioned paradox. Then we compare this new approach to the Service Oriented Architecture, highlight the key (dis)advantages of utilizing Microservice Architecture in building flexible automation systems that fits in 4thindustrial revolution needs, and describe the challenges to its future adoption.

The main challenge of exposing IEC61499 or IEC61131-3 Function Blocks as a service remains in adopting service-oriented concepts in function block programming. Implementing an IEC61499 or IEC61131-3 Function Block that is being accessed via service-oriented protocols is straight forward. The main challenge remains in modeling a Function Block as a service. Adopting service-oriented concepts like Service Oriented Architecture or Microservice Architecture requires tackling challenges like service granularity, (de)composition, etc. For instance, too coarse-grained services could lead to significant drawbacks, while too fine-grained services could increase the system's overall complexity, introducing semantic tight coupling and bringing about communication overhead. Therefore, understanding whether a service (de)composition is adding any value could help us to identify the best service granularity. Finding the best service granularity means knowing how many Function Blocks could be exposed into one service. This could undeniable lead to improvement in resource consumption especially in constraint environments. In this paper we design a cost analysis function for calculating the overhead of service decomposition. This work will help to answer one of the most important aspects of the service-oriented approach, called service granularity in the scope of Function Block as a Service.

An emerging trend in industry 4.0 is to use wireless communication infrastructure and mesh networks in applications requiring high reliability and safety. Although not a typical industrial production process, railway vehicular networks are also an industrial application which come with stringent reliability and safety requirements. Current research is focusing on using vehicular networks as an enabling technology to actively control the separation between two consecutive vehicles, enforcing a safe distance which is nevertheless much shorter than currently used to maintain vehicle separation. In this respect, we analyze a hopping strategy for Time-Slotted Channel-Hopping (TSCH), which was introduced in the IEEE 802.15.4e amendment with a view of improving the reliability of IEEE 802.15.4 networks. We define a probability framework to estimate the chance of successful hopping assuming two previously merged vehicles, and we design a zero-sum game and propose a payoff function to always place communicating nodes in a Nash equilibrium by choosing whether to hop or not, and therefore maximizing the communication throughput by mitigating jamming signals.

Industrial control system is a general term that addresses several types of control systems, including supervisory control and data acquisition systems, distributed control systems, Programmable Logic Controllers and etc. There is no doubt that protecting PLCs from cyber-attacks is very important as they directly control industrial processes. In critical infrastructure, any successful attack on PLC could be as serious problem particularly in DCS. In this paper we approach an authentication solution based on cryptography to avoid unauthorized accesses in ICS.

TIEC 61499 defines an execution model for distributed industrial control applications, i.e. a single application distributed among several devices. In such an environment partial failures are likely to occur. In order to avoid probable system malfunctions and breakdowns due to partial failures, the authors have previously proposed a framework where the concept of replication may be applied to the IEC 61499 execution model. This paper focuses on describing an implementation of this replication framework on the FORTE IEC 61499 execution platform, along with the results of the first tests of the implementation. A set-up for the full validation of the approach is also described.

In a modern industrial environment control programs are distributed among several devices. This raises new issues and challenges especially in failure modes. Building fault tolerant applications can be the solution in order a failure of one sub-component not to jeopardize the execution of the whole application. The authors have proposed a framework to support replicated IEC 61499 applications. In this paper we augment this framework with the support for different voting strategies, propose an extension of the replication communication protocol, and analyse the resulting fault-tolerance semantics. A limited implementation of the framework is also described.