Organizing reuse for production systems engineering with capabilities and skills

Abstract

The flexibility of production systems is a key factor for Industry 4.0. Capabilities and skills (C&Ss) aim at improving engineering flexibility along the production system life-cycle by decoupling production processes and resources. However, traditional reuse approaches in production systems engineering, such as the VDI 3695, do not yet consider C&Ss. This paper proposes the Capability and Skill Reuse (CSR) framework to define how VDI 3695 activities require adaptation for C&S models. The paper analyzes how the framework can facilitate reuse along the production system life-cycle and identifies open issues for research.

Full text

at– Automatisierungstechnik 2023; 71(2): 116–126
Methods
Kristof Meixner*, Felix Rinker, Laura Waltersdorfer, Arndt Lüder and Stefan Biffl
Organizing reuse for production systems
engineering with capabilities and skills
Organisation der Wiederverwendung im Engineering von Produktionsystemen mit
Capabilities und Skills
Adapting the VDI 3695 procedure model to reuse with capabilities and skills
Eine Anpassung des VDI 3695 Vorgehensmodells für Wiederverwendung mit Capabilities
und Skills
https://doi.org/10.1515/auto-2022-0120
Received September 19, 2022; accepted November 18, 2022
Abstract:The exibility of production systems is a key
factor for Industry 4.0. Capabilities and skills (C&Ss) aim
at improving engineering exibility along the production
system life-cycle by decoupling production processes and
resources. However, traditional reuse approaches in pro-
duction systems engineering, such as the VDI 3695, do
not yet consider C&Ss. This paper proposes the Capability
and Skill Reuse (CSR) framework to dene how VDI 3695
activities require adaptation for C&S models. The paper
analyzes how the framework can facilitate reuse along the
production system life-cycle and identies open issues for
research.
*Corresponding author: Kristof Meixner, Christian Doppler Labo-
ratory SQI, TU Wien, Vienna, Austria; and Institute of Information
Systems Engineering, TU Wien, Vienna, Austria,
E-mail: kristof.meixner@tuwien.ac.at.https://orcid.org/0000-0001-
7286-1393
Felix Rinker, Christian Doppler Laboratory SQI, TU Wien, Vienna,
Austria; and Institute of Information Systems Engineering, TU Wien,
Vienna, Austria, E-mail: felix.rinker@tuwien.ac.at.https://orcid.org/
0000-0002- 6409-8639
Laura Waltersdorfer, Institute of Information Systems Engineering,
TU Wien, Vienna, Austria; and Semantic Systems Research Lab, TU
Wien, Vienna, Austria, E-mail: laura.waltersdorfer@tuwien.ac.at.
https://orcid.org/0000-0002- 6932-5036
Arndt Lüder, Institute of Ergonomics, Manufacturing Systems and
Automation, Otto-von-Guericke University, Magdeburg, Germany,
E-mail: arndt.lueder@ovgu.de.https://orcid.org/0000-0001- 6537-
9742
Stefan Biffl, Institute of Information Systems Engineering, TU Wien,
Vienna, Austria, E-mail: stefan.biffl@tuwien.ac.at.https://orcid.org/
0000-0002- 3413-7780
Keywords: capabilities; exibility; reuse; skills.
Zusammenfassung:Die Flexibilität von Produktionssyste-
men ist ein wesentlicher Faktor für Industrie 4.0. Capabili-
ties und skills (C&Ss) bezwecken die Flexibilität entlangdes
Lebenszyklus von Produktionssystemen zu verbessern,
indem sie helfen Produktionsprozesse und -ressourcen
zu entkoppeln. Traditionelle Wiederverwendungsansätze
im Engineering, wie die VDI 3695, berücksichtigen C&Ss
jedoch noch nicht. Dieser Beitrag schlägt das Capability
und Skill Reuse (CSR) Rahmenwerk vor, um zu denieren,
wie VDI 3695-Aktivitäten für C&S-Modelle Angepassungen
erfordern. Der Beitrag analysiert, wie das Rahmenwerk
die Wiederverwendung entlang des Lebenszyklus’ von
Produktionssystemen erleichtern kann und identiziert
oene Fragen für die Forschung.
Schlagwörter: Capabilities; Flexibilität; Wiederverwen-
dung; Skills.
1 Introduction
Key factors for the Industry 4.0 transformation are the
exibility and adaptability of production systems to manu-
facture a range of products from a product portfolio [1,2].
Further, the Industry 4.0 vision concerns connecting single
production systems to production networks for enabling
production as a service (PaaS).
An established approach to model the functionality of
a system in Production Systems Engineering (PSE) is the
Product-Process-Resource (PPR) approach [3]representing
products, production processes, and the necessary pro-
duction resources. However, in PSE practice, production
Open Access. © 2022 the author(s), published by De Gruyter. This work is licensed under the Creative Commons Attribution 4.0 International
License.

K. Meixner et al.: Organizing reuse for PSE with capabilities and skills |117
processes and resources, and their models,are often tightly
coupled, impeding production exibility. Complementing
the PPR approach, capabilities and skills (C&Ss) aim to
support exibility along the production system life-cycle
by decoupling and abstracting production processes and
their requirements from the production resources that
execute these processes [4]. For instance, recent research
proposed formal and machine-readable C&S descriptions,
e.g., using ontologies, to overcome tacit expert knowledge
[5,6]. Such semantic descriptions also aim at an automated
matching of production process requirements to resources,
easing PSE and lowering manual work that is prone to error
[7]. Further works investigated the automated derivation
of capability descriptions along with executable skills [8].
Machine-readable capability and skill (C&S) descriptions
combined with automated matching and decoupled exe-
cutable production services should facilitate the required
exibility and creation of production networks.
A crucial prerequisite for ecient and high-quality
PSE and operation is the systematic reuse of engineering
artifacts, such as resources with their models and reference
sheets. Systematic reuse promises to reduce engineering
cost and time to market, lower maintenance eort and
improve the quality of products [9]. Jazdi et al. [10]investi-
gated the project-independent activities (PIAs) of VDI 3695
[11] to improve the eciency of PSE by increasing artifact
reusability. The same applies to C&Ss, where reusability
and reuse were identied in a recent literature survey as
both a requirement for and a benet of using C&Ss [4]. This
especially holds in distributed environments, such as PaaS.
However, to the best of our knowledge, the elicitation
of C&Ss from existing engineering artifacts, such as PPR
models, for their systematic reuse has not been reported.
Therefore, we aim in this paper to address the research
question: How do VDI 3695 activities for domain and
application engineering require adaptation to facilitate
reuse with capabilities and skills in PSE?
To address this research question in this work, we
provide the following contributions. We categorize require-
ments towards C&Ss from a recent literature survey [4]and
investigate how these requirements need to be considered
to facilitate C&S-based reuse. We propose the Capability
and Skill Reuse (CSR) framework for the elicitation of C&Ss
from engineering models and artifacts and their reuse.
Therefore, we describe how the VDI 3695 reuse activities
for domain and application engineering in PSE require
adaptation to enable C&S-based reuse. Further, we discuss
the benets and limitations of C&S models as a foundation
to facilitate reuse along the production system life-cycle.
The remainder of the paper is structured as follows.
Section 2 describes the background and related work on
knowledge representation and reuse in PSE. Section 3
categorizes requirements towards C&S and introduces the
Capability and Skill Reuse (CSR) framework for the reuse
of production system models and artifacts. Sections 4 and
5discuss the research results and conclude.
2 Background
This section summarizes the background and related work
and sketches an illustrative use case.
2.1 Knowledge representation in PSE
PSE consists of several life-cycle phases, from basic
and detailed planning to commissioning and operation.
Additionally, PSE takes place in a multidisciplinary
environment, where engineers from various domains,
such as mechanical or electrical engineering, maintain
dierent views on the production system [12]. The PPR
approach [3] unies three main aspects of PSE. The
model represents input and output products, production
processes required to transform input into output
products, and production resources that automate the
production processes. The Formal Process Description
(FPD), dened in the VDI 3682 [13], provides a visual and
formal model to describe these aspects.
Pfrommer et al. [14]introducedskills as a comple-
mentary element to PPR. They dened skills as semantic,
vendor-independent representations of process function-
ality required by a product and provided by a resource.Ked-
dis et al. [15] distinguished required capabilities,denedin
production step plans, from provided capabilities,imple-
mented by resources.While a recent literature survey found
early literature on C&S to use the concepts interchangeably
[4], later works distinguished more clearly between C&S.
Nevertheless, both concepts aim to abstract and decouple
processes and resources for more exible production.
Several works proposed models for C&S, including
their relations to PPR, and formal machine-readable speci-
cation, e.g., via ontologies [5,16,17]. Järvenpää et al. [7]
investigated how formally described resource capabilities
can be automatically matched to product requirements.
Furthermore, recent research studied the automated
derivation and execution of skills, e.g., via OPC UA [8,18].
This paper builds on the PPR and C&S concepts, in par-
ticular, on the denitions and the model of C&S described
in [19]. In their model, capabilities are implementation-
independent specications of functions in industrial

118 |K. Meixner et al.: Organizing reuse for PSE with capabilities and skills
production. While production resources can provide such
capabilities, production processes can require them,
encapsulating the product requirements. On the other
hand, skills are executable implementations of capabilities
on a resource (cf. Figure 1), where several skills might
realize a capability.
2.2 Knowledge reuse in PSE
Jazdi et al. [10] investigated how PSE eciency can be
increased by identifying reusable engineering artifacts and
systematically using them extensively in upcoming engi-
neering projects. Their work is based on the VDI 3695 pro-
cedure model for project activities [11]andthetwo-life-cycle
model from Software Product Line Engineering (SPLE) [9].
The VDI 3695 [11] for optimizing engineering organi-
zations describes a two-phase procedure model.Themodel
consists of project-independent activities (PIAs) to iden-
tify and provide reusable artifacts and project-dependent
activities (PDAs) that use these artifacts (cf. Figure 2). The
PIAs for domain engineering consist of (i) an analysis of
the domain and artifacts suited for reuse, (ii) the planning
of a reference architecture and reusable artifacts, and (iii)
the realization and testing of reusable artifacts. Jazdi et al.
[10] translate these activities into detailed tasks for PSE.
The VDI 3695 species ve target states of reuse maturity
in PSE that range from isolated reuse by single engineers
to reuse with reference models and standards. The PDAs
for application engineering consist of (i) the acquisition
and requirements engineering of new PSE projects, (ii) the
planning and realization of a production system or produc-
tion services using the reference architecture and reusable
artifacts, and (iii) commissioning of the realized system and
services. Ideally, requirements, acquired knowledge, and
Figure 1: PPR model for a screwing process in VDI 3682 [13] notation
without (dashed connection executes)andwith C&Ss.
artifacts from the individual projects are inputs to the PIAs
(cf. Figure 2, dashed arrow).
Similarly, SPLE investigates the reuse, exibility, and
conguration of software portfolios and their engineering
[20]. Therefore, van der Linden et al. [9]identiedthe
four fundamental principles of variability management,
business-centric and architecture-centric engineering, and
the two-life-cycle approach. The two-life-cycle approach
describes domain engineering and application engineering,
similar to PIAs and PDAs of the VDI 3695 [11]. The reusable
artifacts are stored in a common artifact repository (cf.
Figure 2) for use in the PDAs. SPLE also investigated
models and methods to represent and manage variability
in artifacts and their conguration. Two SPLE approaches
to model and congure variability, also mentioned by Jazdi
et al. [10], are feature modeling and decision modeling [20].
A recent survey [4] elicited expected requirements
towards C&S and benets of C&S in PSE. The survey
reported reusability both as a requirement to enable
C&S-based PSE and as a benet as C&Ss foster reuse of
knowledge. However, to the best of our knowledge, very
little work on the systematic reuse of C&S in PSE has been
reported. Therefore, this paper investigates the reuse in
and for C&S-based PSE, in particular, the elicitation and
abstraction of C&Ss from engineering artifacts, such as PPR
models.
2.3 Illustrative use case
To illustrate the CSR framework, this section reports
on a use case abstracted from real-world applications.
These applications stem from engineering organizations of
high-performance automation for car part manufacturing
in Germany and Austria [21]. In particular, we consider
joining processes of large car parts, such as doors, to car
bodies.
In the use case, we consider a system integrator which,
for particular customers, plans and engineers work line
production systems that manufacture a portfolio of car
parts automated in typical car production plants. The
plant operators should be able to oer their production
services in a marketplace in the future, aiming at PaaS.
Therefore, the system integrator wants to reuse existing
well-described engineering artifacts, such as robot cell
models, for various company-wide projects. To this end,
the solution candidates should be decoupled from specic
product and production process requirements of previous
projects.
Figure 1 shows a section of a PPR model in VDI 3682
notation [13] with the products (represented as circles in
a blue frame), e.g., the door, one process step (depicted

K. Meixner et al.: Organizing reuse for PSE with capabilities and skills |119
Figure 2: The Capability and Skill Reuse (CSR) framework for PPR models and artifacts, based on the VDI 3695 guideline [11].
as a rectangle in a red frame), i.e., the door screwing
process, and a resource (shown as a rounded rectangle
in a yellow frame), i.e., the screw-driving robot. A corre-
sponding engineering artifact can be, e.g., the model in
the Product-Process-Resource Domain-Specic Language
(PPR–DSL) [22].
In the use case, the door is mounted to a car body
with screws. The screws have dierent types depending on
the doors, which have dierent dimensions. The processes
have technical and economic requirements, such as the
required torque or the production rate. Furthermore, the
processes need to consider the characteristics of the
products, i.e., the torqueand dimension. The screw-driving
robot has several characteristics, such as torque or rate
range, required for correct process execution. While some
of these characteristics are similar in the assembly line,
others are variants of originating processes and resources.
Traditional PSE and reuse [10,23] often maintain a
quite resource-centered perspective, where processes are
modeled only as part of the resource and its behavior (cf.
dashed red arrow in Figure 1).
In C&S-based PSE, the process requirements are mod-
eled as required capabilities, e.g., a screwing capability (cf.
Figure 1) or even more abstract a joining capability.How-
ever, some characteristics, such as electric or pneumatic
screwing, might be irrelevant to the production processes.
Resources, such as screw-driving robots, on the other
hand, provide the means to execute a functionality, in this
case, to join two parts, respectively, screw them together.
In C&S-based PSE, the functionalities of resources are
modeled as provided capabilities and implemented as, e.g.,
skills [19]. This way, the required and provided capabilities
can be matched, e.g., in the engineering phase or on a
marketplace.
3 The CSR framework for reuse with
capabilities and skills
This section categorizes requirements for C&Ss regarding
their relevance for reuse and presents the Capability and
Skill Reuse (CSR) framework.
3.1 Requirements towards capability- and
skill-based engineering and reuse
Froschauer et al. [4] elicited requirements towards C&Ss
in a literature survey. We categorize these requirements
to identify which of them are particularly relevant in
what reuse activity of the CSR framework. In Table 1,we
introduce four categories and assign each requirement to
one of them.1In the next section, we use this categorization
to highlight the relevance of the particular requirements in
the activities of the CSR framework.
The rst category concerns the description of capa-
bilities to support their interpretation by machines and
humans, exchange, and ideally openness [24]. Therefore,
capability descriptions shall be formal and vendor-neutral.
1Note that the requirement reusability in [4] is not part of this
categorization due to the overall focus of this paper on reuse.

120 |K. Meixner et al.: Organizing reuse for PSE with capabilities and skills
Table 1: Categorized requirements for capabilities and skills.
Category Requirements
Capability description Vendor-neutral
Formal
Capability and skill selection Identifiable
Classifiable
(Auto-)discoverable
Matchable
Skill implementation time (Re-)configurable/Adaptable
Modular
Extensible
Skill run time Executable
Stateful/deterministic
Scalable
Communication interface
To facilitate the selection of C&Ss, i.e., the appropriate
selection of C&Ss for a purpose, during the PSE life-cycle,
they shall be (i) identiable2for reliable distinction (ii)
classiable to categorize C&Ss according to well-known
PSE semantics, e.g., the DIN 8580 [25], (iii) matchable
to automatically nd suitable production resources for
production requirements, and (iv) discoverable to nd
production services in a distributed environment, e.g., on
amarketplace.
Skills encapsulate the functionality of a production
resource implementing a particular capability. Therefore,
they need to fulll requirements at implementation and
at run time. During the implementation time of a skill,
engineers need to consider the following requirements
with the aim of exibility and usage variability. A skill
should be (i) congurable respectively adaptable, to choose
from their internal variations [9], (ii) modular to combine
them to higher-level functionality, and (iii) extensible to
adapt them for future purposes.
At production system run time, skills shall be (i)
executable to run directly on a resource, (ii) stateful
respectively deterministic for reproducibility and to know
their current state, (iii) scalable to deploy them to many
similar resources and handle growing productionrequests,
and (iv) provide a communication interface to control their
behavior.
2For instance, the RFC 2396 URI syntax provides a scheme for
identiable assets – https://www.rfc-editor.org/rfc/rfc2396.
3.2 Activities for capability- and skill-based
reuse of PPR artifacts
This section introduces the Capability and Skill Reuse
(CSR) framework for reuse in PSE with C&Ss. Figure 2
shows the PIAs and PDAs of the VDI 3695 procedure
model [11]. This paper focuses on the activities depicted
in blue, i.e., the core activities of domain and application
engineering [9] without considering acquisition. Between
the PIAs and PDAs, Figure 2 further shows the common
artifact repository to store reusable artifacts. Furthermore,
the gure shows the iterative character of the framework as
backow from the PDAs to the PIAs. As a novelty, Figure 2
highlights the activities for engineering with C&Ss based
on reusable PPR artifacts (areas in grey).
The rst four activities of the CSR framework concern
the PIAs of the VDI 3695 procedure model for domain
engineering.
PIA.1 – Model and artifact analysis. This activity
maps to the analysis PIA of the VDI 3695.
In this activity, engineers responsible for company-
wide reuse analyze the domain and its requirements. The
result is a reference model for the domain, such as the
system architecture for a work line in car manufacturing.
This reference model can specify common requirements
but also technical solution elements for the PDAs. Fur-
thermore, the engineers analyze existing artifacts, like
PPR models in PPR–DSL [22], from previous projects to
assess their reuse potential. The analysis aims to nd and
document artifacts that have been used in several projects
and that engineers can adapt for more generic use. In the
context of the use case (cf. Section 2.3), such artifacts could
be PPR models of screwing processes with parameters in a
similar range, like the torque or workpiece dimensions.
In the traditional approach, the engineers often do
not dierentiate between the products, processes, and
resources in the analysis. For instance, engineers analyzed
and collected resources for reuse in future projects at one
company from the use case but mixed them with concrete
products rather than, e.g., more generic dimensions. While
such an analysis is ecient for local engineering, it makes
reuse beyond local environments riskier and less ecient.
In the CSR framework, the reuse engineers pursue
two goals to nd and document reuse candidates. First,
they identify processes in the artifacts independent of the
products and resourcesthey use, e.g., the screwing process.
Based on that, more generic process characteristics can
be derived in the next activity. The overall goal is to
identify process candidates that seem relevant for required
capability descriptions (cf. Figure 1). Second, the engineers
identify resources in the artifacts that seem promising

K. Meixner et al.: Organizing reuse for PSE with capabilities and skills |121
for reuse, e.g., the screw-driving robot. For instance, one
company in our use case maintains a database of regu-
larly used resources with particular characteristics, such
as power consumption. In another company, a domain
analysis showed that the types of screw-driving robots
could be reduced by grouping them by their functionality
[21]. The overall goal is to identify functionality candidates
that seem relevant as input to describe the functionalities
of these resources as provided capabilities and implement
them as skills.
The result of the analysis (cf. Figure 2 yellow
diamond 1) is a reference model for the domain, e.g., for
joining work lines, and a documentation of (partial) PPR
artifacts identied as processes or resources.This reference
model and the documentation are the inputs for activity
PIA.2.
PIA.2 – Process and resource planning. This activity
maps to the planning PIA of the VDI 3695.
In this activity, the engineers dene the utilization of
the assets from the analyzed PPR artifacts, e.g., usage as
reference assets or parameterized assets in future projects.
Therefore, the engineers need to generalize and categorize
the assets and plan their parameterization, i.e., assess their
variability and conguration options.
In the use case, we consider the PPR model of the door
screwing process. First, the PPR artifacts might need to be
split to single out the section with the screwing process.
Then, the engineers need to generalize the products as
the products are most likely dierent in other projects.
For instance, the type of screw used, e.g., with a specic
inventory number, needs to be generalized to its relevant
properties, e.g., slotted or Phillips head. Similarly, the
door might be generalized to a workpiece with particular
dimensions. Figure 1 illustrates this generalization of
products as dashed outlines in activity PIA.2.
In the traditional approach, process and resource
assets are often mixed or merged in the artifacts. For
instance, the screw-driving robot might be modeled to
directly manipulate the products,only implicitly represent-
ing a screwing process. Thus, artifacts resulting from this
planning activity are less modular and decoupled and,
hence, represent the requiring and provisioning side of
production insuciently.
In the CSR approach, the engineers decide which
(parts of the) artifacts concern process capabilities, i.e.,
required, or resource capabilities, i.e., provided. If an
artifact mixes process requirements and resource func-
tionality, the engineers plan how to separate the process
from the resource descriptions. In the use case, the PPR
artifact requires splitting or remodeling to separate the
process and the resource, e.g., into dierent artifacts that
can then be imported as libraries. The engineers must
then categorize and group the processes and resources
by similar requirements and functionality. This task can
follow domain-specic guidelines, such as the DIN 85803
for manufacturing methods. For instance, screwing and
welding processes can be part of a higher-level group of
joining processes. Similarly, catalogs, such as company-
specic taxonomies or databases or the EClass standard,4
can help to categorize resources.
The result of the planning activity (cf. Figure 2
yellow diamond 2) are separated and categorized processes
(with generalized products) and resources. These resulting
artifacts are the input for activity PIA.3.
PIA.3 – Capability and skill elicitation and mod-
elling. This activity maps to the PIAs planning and
realization of the VDI 3695.
In this activity, domain engineers realize the reusable
assets as PPR artifacts. For instance, they create templates
from particular assets that can be parameterized and
reused in dierent PSE projects.
In the traditional approach, such PPR template
designs often consist of resources only that realize the
functionality for the production of a product. Therefore,
the resulting artifacts concern productand process require-
ments as well as the functionality of particular resources
like robots. While this mightmake the conguration of such
templates easier, it makes, e.g., the exchange of resources
solely based on the required functionality harder [7].
In the CSR framework, the domain engineers elicit
and model processes and their requirements as process
capabilities. In several cases, the engineers might want
to aggregate the found process requirements for an
abstraction to higher-level groups, e.g., serving a range
of parameter values [26]. Similarly, the engineers model
the resource functionality as capabilities and potentially
implement them as skills. Modeling the C&Ss requires
using appropriate models or languages, such as ontologies
[5,17] or domain-specic languages [22]. For the skill
implementations, engineers can utilize technologies, such
as OPC UA [8,18] or PackML.5
In the use case, we would model the screwing process
as required capability, e.g., in a process ontology [5], with
the required rate, torque, and screw type as congurable
parameters. The screw-driving robot would be modeled
3DIN 8580 – https://standards.globalspec.com/std/1742169/DIN
%208580.
4EClass – https://eclass.eu/en/eclass-standard.
5PackML – https://www.omac.org/packml.

122 |K. Meixner et al.: Organizing reuse for PSE with capabilities and skills
as provided capability with its rate and torque range,
i.e., the minimal and maximal values, e.g., 100 Nm to
200 Nm. Furthermore, the concrete functionality of the
screw-driving robot would be implemented as a skill,
e.g., with specic control software, that implements the
provided capability.
The capabilities shall fulll the capability description
and C&S selection requirements (cf. Table 1)thatarethen
relevant in the PDAs. Similarly, the skill implementations
shallfullltheimplementation time requirements. While
this is an extra eort in this step, fullling these require-
ments pays o in the project-dependent realization.
The result of the realization is modeled as C&Ss
that are deployed into the common artifact repository
using an agreed-on structure. Figure 2 illustrates these
artifacts as processes with generalized products with their
corresponding capabilities in blue and as resources with
their corresponding capabilities (and skills) in magenta.
PIA.4 – Capability and skill validation. This activity
maps to the testing PIA of the VDI 3695.
After modeling the capabilities and implementing the
skills, the provided C&Ss must be tested and validated
to qualify them for the production systems. This task
should already be executed on physical resources, such
as a testbed, indicated by the cog wheel in the resources.
Therefore, skills must fulll the run time requirements.
This means, they need to be executable,stateful and
deterministic,andscalable [4]. Furthermore, they need to
have a communication interface to control their behavior.
The artifacts resulting from the PIAs are stored in the
common artifact repository for use in the PDAs.
The activities in the lower part of Figure 2 concern the
project-dependent activity(PDA) of the VDI 3695 procedure
model.
PDA.1 – Product portfolio analysis. This activity
maps to the planning PDA of the VDI 3695 and is similar in
the traditional approach and the CSR framework.
In this activity, application engineers analyze the
product portfolio that the production system should
manufacture. Therefore, they investigate its production
requirements, such as quality concerns or the planned
order quantity, based on input from the acquisition activity.
Figure 2 shows a product portfolio as small product icons.
For instance, in the use case, a range of dierent doors
types shall be mounted to similar types of car bodies.
In the use case, the engineers analyze the doors and
car bodies with their commonalities and variability. From
this analysis, they can derive which products are similar
enough to manufacture them on one production system,
e.g., door type Aand Bwith similar dimensions in a robot
cell.
The result of this analysis shall be a bill of materials
for the products with corresponding variability and cong-
uration models [9]. In Figure 2 the red label 1 at the lower
part represents the results that are input to PDA.2.
PDA.2 – Capability planning. This activity maps to
the planning and realization PDAs of the VDI 3695.
In this activity, application engineers receive the
production system requirements and the product portfolio
analysis from PDA.1. From this data and the reference
architecture from PIA.1, they derive a suitable production
system architecture. Second, the application engineers
dene the requirements and the functionality for the
products’ single production steps. Therefore, they take
up the analyzed product portfolio, investigate ways to
assemble these products, and derive properties for the
production steps. In the use case, the engineers decide,
e.g., to mount the doors to the car body with screws of a
certain type using a screwing process with a specic torque
and rate.
In the traditional approach, the engineers often
dene a bill of processes and tie them to reusable resource
templates from the common artifact repository. However,
without adequate abstraction, this limits the exchange
and reconguration of resources and impedes the search
for adequate production services, e.g., in a production
network.
In the CSR framework, the engineers take up the
product portfolio description to plan the capabilities
required to produce the products. In the use case, the engi-
neers dene that a door is screwed to the car body, e.g., with
a Phillips and 150 Nm torque. Based on these requirements,
the engineers search in the common artifact repository
for process capabilities that t their requirements, i.e., a
screwing capability with conguration parameters for the
screw head and the torque. Therefore, the capabilities have
to fulll the requirement categories capability description
and C&S selection (cf. Table 1) to nd suitable reusable
capabilities in the common artifact repository.
In the second step, the engineers congure the
retrieved capabilities with the known values of the prod-
ucts from the product portfolio. In the use case, this means
conguring a screwing capability with, e.g., the required
torque of 150 Nm ±5 Nm, and the required Phillips screw
head. Modeling classes of parameter ranges can be helpful
to support better matching to provided C&Ss in the next
step.
Figure 2 illustrates the resulting congured capabil-
ity as a PPR model with concrete products and a congured

K. Meixner et al.: Organizing reuse for PSE with capabilities and skills |123
process capability in blue. These congured capabilities
(cf. red diamond 2 in Figure 2) are then inputs to PDA.3.
PDA.3 – Capability and skill matching. This activity
maps to the planning and realization PDAs of the VDI 3695.
In this activity, the product requirements, expressed
through process descriptions, must be matched and bound
to concrete production resources. The resources must then
be congured to execute the processes correctly.
In the traditional approach, the engineers manually
match the process requirements to resources from the
common artifact repository. This step is mainly based
on implicit knowledge by a single key engineer. A major
limitation of this approach is the need for experts with high
domain knowledge suitable to conduct this task. Thus, this
task is challenging, error-prone, hard to teach, and limited
by the availability of these key experts.
In the CSR framework application engineers use
computational support to match the partially congured
process capabilities with resource capabilities. Therefore,
the tooling environmentshall enable to match C&S descrip-
tions. The selection requires C&Ss to be (cf. Table 1)
identiable to nd unique ones, classiable to search for
them systematically, discoverable to retrieve them from the
common artifact repository, and matchable to assign them
to the required process capabilities. Ontology reasoning is
a promising approach to match C&Ss [7]. In the use case,
we would set up, e.g., an ontology query that searches
for provided capabilities with a torque range that includes
the congured torque of 150 Nm. The result would be the
previously described provided capability with a torque
range from 100 Nm to 200 Nm. Similarly, other provide
capabilities with torque ranges around 150 Nm could be
returned. Furthermore, the engineers can now select from
dierent skills that implement these capabilities, e.g.,
based on robots that they regularly use in their projects.
The results of this step are matched required and
provided capabilities (cf. red label 3 Figure 2)thatareinput
to PDA.4.Figure 2 depicts the icon of the processes with
concrete products and their required capabilities that are
matched to one or more capabilities.
PDA.4 – Capability and skill conguration. This
activity maps to the planning and realization PDAs of the
VDI 3695.
In the traditional approach, one of two cases applies.
If the artifacts are tightly coupled, they require adaption to
the particular project. If the artifacts are loosely coupled,
they require adaption to each other and the project. This
specic adaptation makes it hard to exchange production
resources in case they do not t as expected.
In the CSR framework, the engineers receive C&Ss
from activity PDA.3 that match each other but are only par-
tially congured. For instance, the torque in the screwing
capability has been set to a particular value, in the use case
150 Nm. However, the engineer might need to set further
C&S parameters to concrete values for the production.
Furthermore, the engineers need to bind the particular
capability to the nally selected and congured skill.
In Figure 2 the bound and congured capability and
skill for a process are shown in a PPR model with connected
C&Ss. The results of this step (cf. red label 4 Figure 2)are
input to PDA.5.
PDA.5 – Skill execution. This activity maps to the
commissioning PDA of the VDI 3695.
During commissioning, the designed production sys-
tem runs for the rst time with dierent resource congu-
rations for various products from the product portfolio.
In the traditional approach, the engineers congured
the resources based on product and process knowledge
which is often diluted over the engineering process. While
they might have used reusable artifacts for the congura-
tion, we argue that it is harder to recongure resources in
case they do not prove as ecient or suitable as expected.
In the CSR approach, the nally congured skills are
executed for the rst time on the production system with
the particular conguration. This activity shall ensure,
beyond other things, that the C&Ss arecongured correctly.
To run on the production system, skills must fulll the
same requirements as in PIA.3, where the skills are tested
and validated. Concretely, they have to fulll the run time
requirements of Table 1. Issues during the execution of the
skills shall be fed back directly to the PIAs, e.g., validation
and testing.
Experiences and assets from the PDAs are fed back to
the PIAs to improve the reuse lifecycle.
As a summary, the CSR framework denes activities
that motivate which tasks should be taken to (i) elicit C&Ss
from previous projects, (ii) model and validate them as
reusable artifacts in a common artifact repository, and (iii)
use and congure them in particular engineering projects.
In the next section, we discuss the CSR framework in
context to the related work and research question.
4 Discussion
In PSE, engineering organizations aim at establishing
reuse to improve the quality and eciency of engineering
[11].
This paper investigated the research question: How do
VDI 3695 activities for domain and application engineering

124 |K. Meixner et al.: Organizing reuse for PSE with capabilities and skills
require adaptation to facilitate reuse with capabilities and
skills in PSE?
To address this research question, this paper intro-
duced the Capability and Skill Reuse (CSR) framework that
denes how the VDI 3695 procedure model for reuse for
domain and application engineering requires adaptation
to support but also benet from C&S models.
The CSR framework organizes the design and applica-
tion of C&S models that fulll essential C&S requirements
(cf. Table 1) to facilitate C&S-based reuse in PSE. In
particular, the CSR framework guides engineering activ-
ities to move from traditional reuse of tightly coupled
engineering artifacts for a specic reference architecture
towards an approach aimed at higher reuse. C&S-based
reuse of loosely coupled C&S artifacts facilitates both
internal reuse and the exchange of C&S on a marketplace
with a wider audience, possibly for similar but dierent
reference architectures.
In these contexts, Table 2 lists expected benets of
C&S-based (reuse in) PSE towards exible production [4].
However, these benets require investment into C&S-based
assets, which should be organized in increments that each
provide a benet to justify the cost and mitigate migration
risks.
The activities of CSR framework themselves require
the means and methods of the C&S community. This
includes C&S description methods, such as ontologies [5,
17] and domain-specic languages [22], and technologiesto
implement skills, such as OPC UA [8,18] or PackML/ISA 88.
To this end, the CSR framework requires a futurediscussion
and validation by the community.
The explicit modeling of C&S knowledge represents
currently implicit domain expert knowledge to improve the
automation of designing C&S-based solutions that match
dened process capability requirements. To this end, the
CSR framework facilitates integrating scattered domain
knowledge on reuse from several engineering disciplines,
Table 2: Expected benefits of capabilities and skills [4].
Category Benefits
Usage advancement Flexibility
Automatic matching
Optimization
Interoperability
Development streamlining Planning efficiency
Development efficiency
Reuse support Abstraction
C&S r e u s e
in particular, product and process design, as well as a
variety of detail engineering disciplines [27].
The research in this paper goes beyond the state of the
art in PSE reuse [10,11] and C&S-based engineering (i) by
dening how engineers responsible for reuse can create
and exchange reusable C&S-based engineering artifacts
and models from PPR artifacts and (ii) by illustrating its
applicability in a reuse use case.
The following limitation requires further investiga-
tion. While there are promising contributions towards
C&S-based reuse, experiments and case studies in typical
application contexts are required to provide sound empiri-
cal evidence on the expected benets and associated costs
and risks.
5 Conclusion and outlook
The Industry 4.0 initiative indicated the exibility and
adaptability of systems as a crucial success factor for future
production. The Product-Process-Resource (PPR) concept
aims to provide a model to represent the key aspects of
Production Systems Engineering (PSE). Complemented by
capabilities and skills (C&Ss), which aim to abstract pro-
cess requirements and resourcefunctionality and decouple
them using semantic descriptions, this approach supports
the required exibility for building production networks
[4].
There is maturing work on C&S foundations for
engineering and exchange in a marketplace [28]. However,
less emphasis has been put on the question of how
to combine reuse concerns with C&S-based engineering
to provide a framework for starting and growing C&S-
based engineering in a company. An example are system
integrators that consider providing or procuring solution
elements on a marketplace for C&Ss. However, traditional
reuse approaches in PSE, such as the VDI 3695 guideline
[11] and domain engineering [9,10], do not consider C&S.
Therefore, this paper introduced the Capability and Skill
Reuse (CSR) framework to extend the reuse activities
of the VDI 3695 procedure model towards the use of
C&Ss. Therefore, we build on and integrate basic C&S
representation and processing capabilities [5,8,17,18].
Traditional reuse works well for a system integrator in
a limited domain with well-known solution partners and a
stable set of reference architecture and solution technolo-
gies. However, considering incremental investment into
C&Ss seems advisable if more exibility regarding these
concerns is required. In this context, C&S-based reuse
can facilitate the work of domain experts with computer
functions for reuse processes to use scarce expert resources

K. Meixner et al.: Organizing reuse for PSE with capabilities and skills |125
eciently. Researchers and practitioners in PSE can take
up the results of this research to investigate and improve
reuse in PSE. For instance, they can apply and validate the
framework in various application contexts.
Future Work. Capability and Skill Reuse (CSR) archi-
tecture. We plan to design and explore options for a
software solution architecture for the CSR framework for a
particular domain, such as automotive manufacturing. To
this end, we want to consider aspects of typical reference
architectures and ways for knowledge representation.
Empirical studies of CSR framework applications.
Further, we plan to conduct case studies with system
integrators to detail and validate selected parts of the
CSR framework. For instance, this comprises lifting skill
knowledge fromreuse assets or the co- evolutionof solution
elements in domain and application engineering.
Acknowledgments: The nancial support by the Chris-
tian Doppler Research Association, the Austrian Federal
Ministry for Digital and Economic Aairs and the National
Foundation for Research, Technology and Development
is gratefully acknowledged. The authors acknowledge TU
Wien Bibliothek for nancial support through its Open
Access Funding Programme.
Author contributions: All the authors have accepted
responsibility for the entire content of this submitted
manuscript and approved submission.
Research funding: None declared.
Conflict of interest statement: The authors declare no
conicts of interest regarding this article.
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Bionotes
Dipl.-Ing. Kristof Meixner
Christian Doppler Laboratory SQI,
TU Wien, Vienna, Austria
kristof.meixner@tuwien.ac.at
Kristof Meixner is a researcher at the Christian Doppler Laboratory
SQI at TU Wien. His research interests include aspects of reuse and
variability in capability- and skill-based production systems
engineering. Kristof is a co-organizer of the yearly special session
on capabilities and skills at ETFA.
Dipl.-Ing. Felix Rinker
Christian Doppler Laboratory SQI,
TU Wien, Vienna, Austria
felix.rinker@tuwien.ac.at
Felix Rinker is a researcher at the Christian Doppler Laboratory SQI
at TU Wien. His research interests include aspects of multi-view
engineering knowledge and change workflow management for
Cyber-Physical Production Systems Engineering.
Dipl.-Ing. Laura Waltersdorfer
Semantic Systems Research Lab,
TU Wien, Vienna, Austria,
laura.waltersdorfer@tuwien.ac.at
Laura Waltersdorfer is a researcher investigating Auditable
Semantic AI Systems in the medical science and environmental
context. She has gained research experience in information systems
and data integration approaches in industrial informatics, including
quality assurance and process analysis.
Prof. Dr. Arndt Lüder
Institute of Ergonomics,
Manufacturing Systems and
Automation, Otto-von-Guericke
University, Magdeburg, Germany,
arndt.lueder@ovgu.de
Arndt Lüder is a professor in the field of factory automation leading
the Institute of Ergonomics, Manufacturing Systems and Automation
at Otto-von-Guericke University. His research focuses on the
application of innovative technologies in factory automation
covering control architectures and engineering methodologies.
Prof. Dr. Stefan Biffl
Institute of Information Systems
Engineering, TU Wien, Vienna,
Austria
stefan.biffl@tuwien.ac.at
Stefan Biffl is a professor of Software Engineering at TU Wien. His
research interests include empirical software engineering,
cyber-phycsical production system engineering, software process
improvement, and software quality. He was leader of the 7-year
research project Christian Doppler Laboratory FLEX.