A wide variety of initiatives have now emerged around Industry 4.0. The goal is common to all of them: recognizing the potential for optimizing production processes and individualizing products while minimizing costs at the same time. One of the much-discussed topics in this context is ensuring the transparency of an industrial system, including its stakeholders, machines and products. The Reference Architecture Model Industry 4.0 (RAMI 4.0) was developed with this focus in mind.

The SGAM toolbox: An example of how interdisciplinary collaboration can work in complex systems.

© FH Salzburg

The standardization of RAMI 4.0 is basically intended to ensure the long-term establishment of an architectural description of the factory of the future. However, for many users today it is still a challenge to use it to describe a specific task. The reason for this is the inadequate documentation of this model and the lack of illustrative reference examples. Although it is clear what the boundaries of RAMI 4.0 and its abstraction can look like, there are hardly any specifications available for a detailed classification within the individual layers. The 'Domain Specific Systems Engineering' (DSSE) research group at the Salzburg University of Applied Sciences has tackled precisely this problem and developed software that enables automated model development of industrial systems and relies on well-known technologies such as OPC UA, SysML or Model Based Systems Engineering (MBSE).

Between 2012 and 2017, the SGAM toolbox was developed to tackle the task of developing models for complex systems in the smart grid sector. The SGAM toolbox is a tool that can be used to model tasks based on the Smart Grid Architecture Model (SGAM) - the template for RAMI 4.0. It was developed by the predecessor of the current research group and version 2.0 is currently available for free download.

Falling back on the tried and tested

The results of years of using this toolbox and consultation with industry partners clearly show that interdisciplinary collaboration in complex systems can be considerably simplified with suitable tool support.

The fact that no new technologies were developed, but rather methods that were already known and accepted by the user, made a decisive contribution to this. It therefore made sense to adapt these successfully applied approaches to a new domain such as Industry 4.0. The result is the 'RAMI 4.0 Toolbox'. Developed as an add-in to the 'Enterprise Architect' modeling software from Sparx Systems, it combines systems engineering methods with those of architecture descriptions for the end-to-end development of Industry 4.0 systems. Three core elements are identified: Firstly, the process model, which integrates standards such as ISO 15288 or ISO 42010 and describes a development process. Secondly, the domain-specific language, consisting of models and elements, in order to be able to precisely capture the unique and special features of Industry 4.0. And thirdly, the tool support, which assists the user in terms of usability.

Decomposition of RAMI 4.0

Model Driven Architecture (MDA) provides the basis for the abstraction of RAMI 4.0: ideally, this approach is used to create machine-readable code directly from the system specification.

© FH Salzburg

In order to guarantee cross-sector application of the three-dimensional RAMI 4.0 model, it must first be broken down into its individual parts. Methods from the field of architecture development help with this. Model Driven Architecture (MDA) provides an important approach here. This involves dividing the entire architecture into different levels of abstraction, depending on the described situation. Models and transformations are introduced for this purpose. The aim is to transfer a model in such a way that the same content is prepared for different perspectives. Applied to RAMI 4.0, this means describing the system in a way that is understandable for the end user as a first step.

If, for example, the model of a shoe manufacturer's value creation process is created, all the business players involved, such as suppliers or machine providers and their wishes and requirements, are presented in this phase. This allows the context of the system to be modeled without going into details such as specific production machines or transfer technologies. Comprehensible languages such as UML and its use case diagrams are generally used for this purpose.

The 'Business Layer' of RAMI 4.0 provides the appropriate specification for this by mapping precisely this generic description as the top abstraction level. The functions of the respective components are then depicted in the 'Function Layer' on the basis of the previously specified requirements. These form the basis for the architecture of the system, mapped on the lower layers of RAMI 4.0, where individual technical specifications such as interfaces, data transfer and the modeling of the component itself take place. In the end, machine-readable program code is generated and can be continuously maintained using round-trip engineering. The basic idea behind this process is the complete automation of the technical infrastructure from the previously formally described system design.

While MDA provides the rough classification, ISO 42010 can be used to provide a more concrete architectural description. The stakeholders are identified in the first step. These stakeholders have different interests and requirements for the system, which are represented using so-called 'concerns': For example, the managing director is interested in economic factors, while the network administrator requires information about the ICT infrastructure. ISO 42010 specifies 'views' and 'viewpoints' for this purpose. Different types of models are used to enable different views of the system and thus satisfy the needs of the stakeholders. Technologies such as UML use case diagrams or the Business Process Management Notation (BPMN) are used on the business and function layer.

This makes it possible to visualize the relationships between the individual actors or the production process itself. SysML, a language for describing mainly industrial systems - such as the machines on the production line itself - is used for a detailed analysis in order to deal with detailed design aspects in the final step using modeling languages such as AutomationML.

The RAMI 4.0 toolbox is ultimately a collective of all means and methods that enable the practical implementation of RAMI 4.0.

The RAMI 4.0 toolbox

The three main components of the toolbox are the domain-specific language, the modeling templates and reference data on the one hand, and the add-in for providing this data on the other. The foundation of the toolbox is represented by Enterprise Architect (EA). Both the domain-specific language and the add-in are dependent on its functionality. A setup is available for this purpose, which integrates the toolbox into the respective EA installation environment and extends its range of functions. Generic UML diagrams are supplemented by domain-specific elements and thus allow the description of the different models, specified on the respective levels of RAMI 4.0. To support this, the model templates are demo models that demonstrate the peculiarities and special features of each individual layer of RAMI 4.0 as a kind of tutorial to facilitate the introduction to the creation of Industry 4.0-based architectures. These models are kept on a small scale with only a few system elements, so that only a stitch through the example is given, on the basis of which individual models can be created. They also have comments and instructions on the correct development process.

A major advantage of Enterprise Architect is its individual expandability through programming control. The RAMI 4.0 toolbox offers a wide range of functions for automating monotonous tasks and recording user input. These include the evaluation of key performance indicators (KPIs) or the automatic creation of connection elements and their interfaces. Individual models can also be exported as 3D models for a better overview. The resulting high degree of usability saves users an enormous amount of time and resources.

The development process

The structure of the RAMI 4.0 toolbox can be visualized using several pillars: Building on Enterprise Architect (EA), its functionality is extended and made available by the add-in.

© FH Salzburg

The development of a complex industrial system should be well thought out. This means that a specially defined development process ideally controls the structuring of the system through to adaptation to the previously explained architecture description of RAMI 4.0. The individual process steps are compared with the model transformations of MDA. The ISO 15288 standard, which describes the service life of systems, is suitable for this purpose. In addition to various management processes, such as resource, risk or quality management processes, the technical processes are primarily used here. These include requirements analysis, architecture development and implementation through to the evaluation and rejection process.

To summarize, Domain Specific Systems Engineering (DSSE) controls the creation of the system in three phases. In the system analysis phase, the conditions and boundaries are defined. The system architecture phase then serves to describe the components as so-called 'black boxes' in order to show their interrelationships and connections. In the design phase, each component is now represented as a 'white box'. This allows the various states and parameters of each individual component to be recorded.

Application examples from practice

Ensuring the practical applicability of the RAMI 4.0 toolbox is crucial for its use. In other words, industrial processes should be simplified and no additional overhead created. For this reason, several industrial use cases have already been modeled - including the development of individual shoes in batch size 1 or the provision of intelligent rails for subway lines. The results of these use cases are available online as a click-through model.

The 'blueprint' for the RAMI 4.0 toolbox, the SGAM toolbox, is already being used internationally and is being applied in a large number of projects. The same benchmark now applies to the RAMI 4.0 toolbox. As there are only a few specifications and standards in this area and even less experience, it is important to constantly evaluate advances from research and industry and to expand or adapt the toolbox accordingly. An agile development process, which constantly iterates through a cycle of development, evaluation and requirements management and thus constantly integrates new results, is beneficial here.

The current version 0.5 of the RAMI 4.0 toolbox already shows what the modeling of an industrial system can look like. The company is cooperating with partners from industry and is constantly working on optimizations and the integration of standards. The current and older versions of the toolbox are also freely available online and contain the progress made in the individual development phases.

The aim is to publish version 1.0 in 2018 and thus take the first step towards cross-company use.

Authors:
Christoph Binder is a Junior Researcher in the DSSE group at the Center for Secure Energy Informatics (ZSE);
Christian Neureiter is group leader of the DSSE group at the Center for Secure Energy Informatics (ZSE);
Oliver Jöbstl is Managing Director of Successfactory Management Coaching.