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and defines optional additional constraints. Products also not time-efficient due to set-up and reset times for the
have an AAS, which contains, for example, quality metrics. transport robot. Thus, separating the transport service into
Orders are also represented by an AAS, which contains, for the steps transportprepare, transportperform, and transportreset
example, information regarding deadlines and the recipe to allowed the time needed for the execution of the
be used for creating the product. Actual data is contained in manufacturing to be greatly decreased. Prepare moves the
AAS sub-models, which define data models for specific robot arm to the source location, perform performs the
kinds of information. The orchestrator accesses the product transport step, and reset moves the robot arm to a waiting
recipe from the order AAS and orchestrates the services of position.
devices through their control components. Every AAS
registers itself in an AAS registry to ensure that it can be Furthermore, SoA is typically not used in the context of hard
found by orchestrators and applications. Applications use real-time constraints. However, direct control of
AAS and AAS sub-models to access information and manufacturing devices imposes this requirement. Thus, in
services with a unified interface, regardless of the type of the SoA, services need to be defined in such a way that they
information provider. are independent of real-time constraints. For example, a
transport service typically has no hard real-time constraints.
4. EXPERIENCES WITH SOA In contrast, a direct control service of a motor (e.g., start/stop)
will most likely have these constraints.
The service-oriented architecture approach is already being
used in the context of different production systems. Areas of 4.2 Migrating legacy devices
application include the integration of production with
product lifecycle management systems, process Another topic of interest is the migration of existing
visualizations using different types of dashboards, or manufacturing systems to SoA. In the authors’ experiences,
retrofitting of existing devices and production lines to SOA especially small and medium.sized enterprises (SME) need
concepts. additional support for performing this migration. Typically,
an SME does not have the necessary expertise for performing
4.1 Changeable production process this transformation. A successful implementation of SoA
requires strong IT knowledge, which often does not exist.
We applied SoA in a production line that manufactures gear Surprisingly, experience has also shown that some SMEs are
boxes for heavy cars. The production line consisted of new also not completely aware of their plant set-up, e.g., of the
devices communicating via Ethernet link, but also included communication protocols used. The reason for this is that
older devices with field bus connections or proprietary small enterprises, in particular, focus on their core business
communication. The goal of this activity was to integrate a and contract third parties for plant set-up and device
new workplace with a smart cordless electronic screwdriver configuration.
for an additional worker. A new workplace had to be
integrated with the existing automation because it needs to
receive tasks and deliver quality assurance data. The
integration usually takes at least a full day for the necessary
software modifications and testing. With a service-oriented
architecture, it was possible to integrate the new workplace
through its asset administration shells in less than 30 minutes.

In this environment, the SoA approach proved its ability to
change an existing production process. As expected, the
SOA enabled quick exchange and extension of service
providers. However, the basic SoA principle typically only
provides syntax interoperability [8], while semantic
interoperability is also of immense importance for the
domain of manufacturing [9]. Only semantic interoperability
ensures that data and orders are properly understood by
production assets. This gap is closed with the AAS and its Figure 5 – Gateway architecture for SoA deployment
sub-models through its defined structure with explicit
support for clear semantics, which allows, e.g., referencing Thus, implementing SoA for manufacturing requires the
arbitrary standards. However, the service definition might
not be trivial. An exposed service should be as complete and involvement of multiple stakeholders with broad knowledge
of IT and manufacturing. However, migration efforts can be
simple to use as possible. On the other hand, in the interest
of process optimization, exposition of service details may be reduced by resorting to preconfigured solutions. For example,
in one of the projects in which the authors are participating,
necessary. In a project for an industry customer, a transport
mechanism realized by a robot arm was migrated to SOA. a gateway is being developed that allows integrating
arbitrary devices into SoA using AAS. The metadata of the
First, a straightforward service definition was used by
exposing a transport service. However, this definition was AAS and its sub-models can be configured via a
comprehensive interface. Additionally, the link between sub-

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