Mohammad R Rasouli

Rob J Kusters

Jos J M Trienekens

Paul W P J Grefen

M Trienekens

Service Orientation in Demand-Supply Chains: Towards an Integrated Framework

Keywords: service orientation, partnership, control, demand-supply chain, framework

Offering customer-centric value through dynamic and networked capabilities is a strategic need in the current business environment. This strategic need can be met by a Service-Oriented Demand-Supply Chain (SODSC) concept. Various direct and indirect notions in different contexts have been developed about SODSC concept. However, the lack of integration between these notions can easily lead to confusion. This paper aims to counter this confusion by providing a framework for structuring various related notions and explaining them through illustrative cases. Based on a cybernetic system approach, the service-oriented value, partnership and control aspects of SODSC have been investigated respectively. On the basis of a distinction between demand and supply chain perspectives, two distinct dimensions of service orientation have been explored in each of the aspects. The resulting integrated framework, visualized by three related two-dimensional matrices and illustrated by real cases, offers the possibility to characterize and analyze the various SODSC notions.

Introduction

The current business environment is characterized by empowered customers and globally networked suppliers. In this environment, the offering of customer-centric value through dynamic capabilities is a strategic issue. This strategic issue has led to the development of new dominant logics, especially in the marketing and operations management contexts [START_REF] Lusch | REFRAMING SUPPLY CHAIN MANAGEMENT: A SERVICE DOMINANT LOGIC PERSPECTIVE[END_REF]. Service-Dominant (S-D) logic as a new paradigm that emphasizes customer-centric value creation has changed the conventional marketing nature from transactional to relational [START_REF] Vargo | Evolving to a new dominant logic for marketing[END_REF]. Also the necessity to provide integrated and life-cycle based product services combinations, rather than single products or services, has transformed the traditional stable supply chains to adaptive supply networks [START_REF] Gebauer | Characterizing service networks for moving from products to solutions[END_REF]. This means that service orientation in demand and supply chains can be conceived as an essential requirement to survive in the current business environment.

The importance of service orientation in the demand and supply chains has led to the development of various related notions such as S-D logic [START_REF] Lusch | REFRAMING SUPPLY CHAIN MANAGEMENT: A SERVICE DOMINANT LOGIC PERSPECTIVE[END_REF][START_REF] Vargo | Evolving to a new dominant logic for marketing[END_REF][START_REF] Maglio | Fundamentals of service science[END_REF] Product Service System (PSS) [START_REF] Tukker | Product-services as a research field: past, present and future. Reflections from a decade of research[END_REF], Industrial Product Service System (IPS 2 ) [START_REF] Meier | Industrial product-service systems (IPS2)[END_REF], service enhanced products [START_REF] Camarinha-Matos | Collaborative networks in support of service-enhanced products. Adaptation and Value Creating Collaborative Networks[END_REF] and solution management [START_REF] Storbacka | A solution business model: Capabilities and management practices for integrated solutions[END_REF]. Although this variety of views and notions helps to understand the different aspects of service orientation, the lack of integration between them can easily lead to confusion. To deal with this confusion, in this paper we apply the Service-Oriented Demand-Supply Chain concept that is reflected by SODSC. This concept addresses the differences between the responsibility of demand chain and supply chain activities for service orientation [START_REF] Hilletofth | Demand-supply chain management: industrial survival recipe for new decade[END_REF]. It reflects the necessity of integration of these activities as well. Based on the SODSC we aim to develop an integrated framework that enables to bring together different related notions.

In this paper, to deal with the complexity and confusion of diverse notions related to SODSC, we distinguish between different aspects and different perspectives (i.e. demand chain and supply chain) of SODSC. The different aspects will be explored separately through a cybernetic system based representation of SODSC. This representation of SODSC includes respectively the service-oriented value, the partnership, and the control of SODSC. This kind of logical reduction of complexity helps to position different service-oriented notions in literature in the integrated framework. The resulting integrated framework, visualized by three related twodimensional matrices, is illustrated by three real cases. The proposed integrated framework along with the illustrative cases enables recognition of different conceivable service orientation transitions. This integrated framework also enables the analysis of the characteristics of a particular organization and its demand-supply chain from the service orientation point of view.

In the next section, the cybernetic system based representation of SODSC is introduced. The distinct aspects of SODSC result from this representation. Also the distinction between supply and demand chain perspectives is illustrated. These aspects and perspectives shape the basis for an investigation and positioning of different service-oriented notions. Subsequently, the three main aspects of SODSC, i.e. service oriented value, partnership and control, are investigated separately in the third, fourth and fifth section. The sixth section provides a discussion on the results of the investigation. The final section concludes the paper and proposes the future research steps to be made.

The Approach for Structuring and Explaining SODSC

As stated before, we will apply cybernetic based system theory to investigate different aspects of SODSC. System theory is based on the idea that basic principles are common to all systems, independent of the area of science to which they belong [START_REF] Bertalanffy | General system theory; a new approach to unity of science. 1. Problems of general system theory[END_REF]. Regarding the multi-disciplinary nature of service orientation [START_REF] Bardhan | An interdisciplinary perspective on IT services management and service science[END_REF], these basic principles of system theory, enable development of an integrated view on the different aspects of service orientation. System theory also provides a terminological setting that is useful to overcome misunderstandings related to the usage of different terms in different contexts.

A system is defined as "a set of interacting or interdependent components forming an integrated whole" [START_REF] Backlund | The definition of system[END_REF]. System approaches can be characterized based on the level of complexity [START_REF] Maglio | Fundamentals of service science[END_REF], but can also be classified as physical, mathematical and cybernetic models, according to the similarity and the degree of abstraction [START_REF] Tukker | Product-services as a research field: past, present and future. Reflections from a decade of research[END_REF]. In comparison with other system approaches, the cybernetic approach is suggested to be used in complex contexts [START_REF] Maglio | Fundamentals of service science[END_REF]. So with respect to the complex nature of SODSC [START_REF] Badinelli | Viable service systems and decision making in service management[END_REF], this approach of system thinking provides proper possibilities to deal with complexity.

To encounter the complexity and confusion in SODSC, a cybernetic system approach reduces the SODSC to its logical aspects. In line with previous research that has developed system based representations of supply or demand chains [START_REF] Verdouw | A framework for modelling business processes in demand-driven supply chains[END_REF][START_REF] Grefen | Hybrid control of supply chains: a structured exploration from a systems perspective[END_REF], we distinguish different aspects of SODSC, see Fig. 1. SODSC can be considered as a system that provides a specific type of output for customers (what) through supportive mechanisms (how) under a certain type of control (why). The clarification of these mentioned aspects leads to a better understanding of SODSC. So, firstly the serviceoriented value is investigated as the output aspect of SODSC. The clarification of different dimensions of service-oriented value, as a core concept in SODSC, facilitates the exploration of service orientation in the other aspects. Secondly, the impact of service orientation on the supportive mechanism aspect in demand-supply chain is investigated. Taking into account the networked nature of SODSC, partnership is explored as the key supportive mechanism aspect. Finally, the characteristics of the control aspect in the SODSC are examined. Since in the networked business environment the main focus is on the strategic alliance/partnership [START_REF] Gunasekaran | Responsive supply chain: a competitive strategy in a networked economy[END_REF], the most important input in our model are the partners that are going to participate in a networked business. So taking into account the partnership as the main supportive mechanism in our model, we don't have to investigate the input aspect separately.

Besides the cybernetic system based reduction of complexity, we also distinguish between demand chain and supply chain perspectives on service orientation. Based on the value chain framework [START_REF] Porter | Competitive advantage: Creating and sustaining superior performance[END_REF], the demand chain perspective focuses on the marketing, sales and customer relationship management activities. The supply chain perspective focuses on inbound logistics, operations and outbound logistics activities. The demand chain perspective responds to the necessity for understanding, creating and simulating customer demand [START_REF] Hilletofth | Demand-supply chain management: industrial survival recipe for new decade[END_REF] and can be recognized as the value creation or the value obtainment system. On the other hand, the supply chain perspective includes all the supply processes to fulfill the customer demand [START_REF] Hilletofth | Demand-supply chain management: industrial survival recipe for new decade[END_REF] and can be called the value delivery system.

By using of foregoing distinctions, we will characterize different service-oriented notions in the three main aspects, respectively: service-oriented value, service-oriented partnership and service-oriented control. In each aspect, in accordance with the distinction between demand and supply chain perspectives, two dimensions of serviceorientation are considered as well, i.e. value obtainment and value delivery. Consequently three two dimensional matrices will be developed in the next sections to investigate the various SODSC notions.

To explain further the characteristics of SODSC notions through the proposed matrices, three real-life illustrative cases will be described. For this purpose, we have chosen three cases of service orientation in the ICT industry. The first case is about Microsoft that has experienced a noteworthy shift from being a supplier of software for IBM personal computers, to a provider of customer-centric products and services through its huge service ecosystem [18]. The second illustrative case of service orientation is the IBM Rational solution for Collaborative Lifecycle Management (CLM) [19]. The CLM is an extensible platform that helps to integrate different related products and services across the software life cycle. The last case is about Accenture's cloud platform that offers integrated hybrid IT solutions [20]. This platform is founded on the integration between different products and services that are provided through different service ecosystems. Each of the mentioned cases describes a different type of service orientation transition that will be discussed based on the proposed framework. This case based illustration can be conceived as the primary step for showing the applicability and generalizability of the proposed framework.

The Service-Oriented Value Aspect of SODSC

The investigation of SODSC depends on a clear understanding of the service-oriented value. Different notions in marketing, operations management and information management contexts have led to confusion about the service oriented value. In our approach, we distinguish between these notions based on the supply chain and demand chain perspectives. On the basis of these two perspectives, two different dimensions of service-oriented value can be recognized in literature as well [START_REF] Kowalkowski | What does a service-dominant logic really mean for manufacturing firms[END_REF]. The first dimension of service-oriented value, i.e. from a demand chain perspective, is established on the basis of customer interaction to create value. The second dimension of service-oriented value, i.e. from a supply chain perspective, is established on extending capabilities of a supply chain to cover the broader requirements of customers through adding new services to the core products of a supply chain.

The first dimension of service oriented value focuses on the interactions between suppliers and customers rather than the ability of a supply chain to provide an extended range of products and services, see Fig. 2, vertical axis. Within this dimension, the emphasis is on the customer centric interactions that shape the value. Within this dimension, the service orientation is reflected by the customer centric definition of the value. This dimension emphasizes the more prominent role of a customer for obtaining the value. It suggests that value is always determined by the customer as value-in-use, whether in direct interaction with the supplier or in indirect interaction through goods in use. Within this dimension of service orientation, value lies not in building more features into products and services such as mentioned in the integrated product services, but in providing more and varied opportunities to consumers for co-creating personalized experiences [START_REF] Bhalla | Collaboration and co-creation: New platforms for marketing and innovation[END_REF].

The second dimension, i.e. the supply chain perspective on service orientation, predicates the ability of a supply chain to deliver new services in addition to the core offerings of a supply chain, see Fig. 2, horizontal axis. This type of service orientation is a supply chain transition from delivering pure products or services to delivering integrated product services packages. This transition is inevitable for companies in mature industries due to the need for higher customer value. Two most important strategic directions that lead supply chains towards the offering of integrated product services can be described as respectively:

1-Time based extension of provider responsibility: from product/service delivery towards product lifecycle management (PLM); Both mentioned dimensions of service orientation, can be considered as customer orientation approaches. However, the first dimension responds to customer orientation through value obtainment activities, whilst the second dimension realizes it through value delivery tasks. The combination of both dimensions leads to offer integrated solutions for customers [START_REF] Martinez | Challenges in transforming manufacturing organisations into product-service providers[END_REF]. It means that offering integrated solutions requires customer-centric interactions as well as the ability of providing integrated product services.

The characterization of the service-oriented value, see Fig. 2, can be illustrated by the cases introduced in section 2. Microsoft's evolution from being a supplier of software for IBM personal computers to co-creating through independent developers, who interact with end users, can be considered as service orientation from a demandchain perspective (i.e. the value obtainment dimension). The IBM's CLM product that supports the entire software development lifecycle from requirement to deployment through integrated and collaborative tooling can be seen as the service orientation in supply perspective (i.e. the value delivery dimension). Also the Accenture cloud platform, that supports hybrid IT solution cocreation through customer interaction with different ecosystems, is an illustrative case for integrated solution cocreation (i.e. the ultimate combination of value obtainment and value delivery dimensions). These illustrative cases show that the proposed distinction between the two dimensions of service-oriented value enables the characterization and the interpretation of serviceorientation in real-life business situations.

The Partnership Aspect of SODSC

The partnership aspect in our cybernetic approach to SODSC, see Fig. 1, describes the alliance of stakeholders to provide service-oriented value. In line with the two distinct dimensions of service-oriented value, i.e. from the demand and the supply chain perspectives, two different dimensions for service orientation of the partnership aspect of SODSC can be recognized. The customer-supplier relationship dimension, established from a demand chain perspective, underlines the role of a customer as an active actor in partnership models that support the customer interaction for value cocreation. The supplier-supplier relationship dimension, established from a supply chain perspective, emphasizes the suppliers' own relationship to aid delivery of integrated product services. These two different dimensions for the characterization of the partnership in SODSC are shown in Fig. 3.

The customer-supplier relationship dimension, see Fig. 3, due to its marketing origination, emphasizes the costumer involvement in value creation rather than the partnership between suppliers [START_REF] Vargo | On value and value co-creation: A service systems and service logic perspective[END_REF]. This dimension is in line with the customer empowerment trend in the marketing context. Customers can engage in dialog with suppliers during each stage of product design and product delivery. This form of dialog should be seen as an interactive process of learning together [START_REF] Payne | Managing the co-creation of value[END_REF]. Customers as active actors to co-create value can take different roles such as co-designer, innovator, marketer and socially responsible actor [START_REF] Romero | Collaborative networked organisations and customer communities: value co-creation and co-innovation in the networking era[END_REF]. In this way, the service ecosystem and value network [START_REF] Lusch | Service, value networks and learning[END_REF] notions have been developed to address new types of partnership. In the service ecosystem, a customer as an active actor coproduces service offerings, exchanges service offerings, and co-creates value [START_REF] Lusch | REFRAMING SUPPLY CHAIN MANAGEMENT: A SERVICE DOMINANT LOGIC PERSPECTIVE[END_REF]. This means that in a value network the supplier-supplier relationship is the subordinate of customer-supplier relationship. In other words, in a value network the customer as a value co-creator determines the suppliers' requirements to respond the customized value.

On the other hand, the supplier-supplier relationship dimension, see Fig. 3, takes into consideration the partnership characteristics that enhance transition from pure products or services towards integrated product services. Delivering result-oriented product services that supports the availability of the delivered value in its whole life cycle requires a strong collaboration between suppliers. Also delivering integrated product services, which is customer oriented in its nature, requires more market sensitiveness in the supplier-supplier relationship. This collaboration between suppliers that can be adopted based on the customer needs to deliver customized integrated product services can be characterized as an adaptive/agile supply network [START_REF] Ivanov | A multi-structural framework for adaptive supply chain planning and operations control with structure dynamics considerations[END_REF][START_REF] Christopher | The agile supply chain: competing in volatile markets[END_REF].

With respect to the characterization of service-oriented value (Fig. 2), partnership mechanisms to support the cocreation of integrated solutions might be characterized by both customer-centric as well as adaptive. This is reflected by the combination of two dimensions of service-oriented partnership in Fig. 3. This type of partnership supports a flexible and dynamic collaboration to respond to the emerging opportunities originated from customer involvement in value creation. The dynamic and opportunity based partnership to deliver the cocreated integrated solution, can be handled through a collaborative value network, see Fig. 3.

In line with the foregoing section, and for a further clarification of the two dimensions of service orientation based on the partnership aspect, we again address the three cases introduced in section 2. Microsoft Partner Ecosystem that supports the cocreation of customer-centric products and services around the Microsoft technologies can be considered as an illustrative case of a value network (i.e. the customer-supplier relationship dimension in Fig. 3). In this ecosystem that consists of 640,000 partners, members interact with customers independently to provide customer-centric value [18].The CLM of IBM can be delivered as a whole package or fragmented parts of the integrated package based on the customer requirements. So the relationship between the suppliers of the different elements of CLM should be adaptive (i.e. the suppliersupplier relationship dimension in Fig. 3). The Accenture cloud platform for the cocreation of integrated solutions might be able to coordinate between suppliers in different value networks. It means that the partnership aspect in support of the Accenture cloud platform consists of the different value networks as well as the adaptive relationship between the suppliers who are members of different value networks (i.e. the combination of the two dimensions of service-oriented partnership in Fig 3). These three cases indicate that organizations pursuing a particular direction for providing service-oriented value require a particular type of partnership characteristics.

The Control Aspect of SODSC

Following the distinction between service orientation in demand and supply chain perspectives, two different dimensions can be addressed of the control aspect as well.

These two dimensions are presented in Fig. 4. Where from a demand chain perspective, the control focuses on the handling of customer-supplier relationship, from a supply chain perspective the control focuses on the coordination between suppliers. The main priority of the first perspective is to lead the system towards a better obtainment of customer satisfaction, where the second perspective emphasizes more efficiency and responsiveness in the delivery process.

The service orientation in the customer-supplier relationship control dimension addresses the shift from a transactional approach for value obtainment towards relational dominant logic (See Fig. 4). The transactional approach as a pre-dominant logic for value obtainment is product-oriented and can be seen as trying to get the customer fitted to the product. The transactional approach for the value obtainment focuses on customer attraction, e.g. through controlling '4Ps' (Price, Product, Promotion and Placement) as the most important variables for the value obtainment [START_REF] Mccarthy | Basic marketing: A managerial approach[END_REF]. However, the relational value obtainment proposes a different approach that is customer-centric rather than product-oriented. The relational value obtainment emphasizes customer experience rather than customer attraction. The customer experience-centric control is based on customers' commitment, trust, satisfaction, communication, and the seller's customer orientation [START_REF] Conway | International relationship marketing-The importance of psychic distance[END_REF].

The second dimension in the control aspect of SODSC describes the coordination between suppliers to provide integrated product services (See Fig. 4). According to the corresponding dimension in the service-oriented value and partnership aspects, the focus of the control aspect in this dimension should be on the handling of agility and flexibility. Handling the agility requires a market sensitiveness capability in the control aspect to understand and respond to the real demands of customers [START_REF] Christopher | The agile supply chain: competing in volatile markets[END_REF]. This leads the control of the relationship between suppliers from forecast-driven to demand-driven. The demand-driven control, which is based on the real customer demand, requires a real-time access to information. So while the conventional suppliers' relationship control is inventory-based, the service-oriented supply chain control is informationbased. This means that the demand-driven control is established on the information that is de-coupled downstream as far as possible. So the real demand information can penetrate into the whole supply chain.

By combining the two mentioned dimensions of service orientation of the control aspect (See Fig. 4) it can be concluded that cocreating integrated solutions through a collaborative value network requires control characterized as relational and information-based. In this case, the control aspect of a system is responsible for handling the relationship between the customer and all the potential suppliers in order to obtain the most fitted value, as well as to organize the suppliers to deliver the obtained customized value. In this case control should be able to manage customersupplier interactions through open dialogue and social interactions and also to coordinate the whole supply chain to deliver the obtained customer centric value. This means that control in the collaborative value network should be capable of handling real time integration between value obtainment and value delivery, (See Fig. 3). In this case, the dynamics of supplier-supplier relationships originates from the customer experience (that is obtained through customer interaction control).

In accordance with the previous sections, the characterizing control aspect in SODSC can also be recognized in the three cases introduced in section 2. It can be conceived that the control aspect in the Microsoft ecosystem through an extended and deep relationship with a broad spectrum of customers can obtain customer-centric values for offering new propositions. While, it seems that IBM's CLM should be able to coordinate between different suppliers to handle different and dynamic demands that are requested by customers. Accenture's cloud platform, being able to offer customercentric integrated solution, should be capable of tracing and obtaining value from different service ecosystems, as well as a dynamic coordination between suppliers to deliver the customer-centric value.

Discussion

The proposed framework for SODSC contributes towards solving the confusion related to the usage of various notions of SODSC. The distinction between the three different identified aspects of SODSC enables an investigation of a broad range of notions in the literature in a structured way. Also the recognition of two different dimensions in each of the three aspects clarifies the different aims of service orientation in the marketing and manufacturing contexts. S-D logic and "service system" notions, which have emerged as the most important scholarly marketing debates in the last decade, emphasize customer-centric value obtainment. While notions such as IPS 2 , PSS, and service enhanced products, that originated from manufacturing and operations management contexts, address the shift from pure product manufacturing towards integrated product services delivery. This type of extreme distinction helps to get a clear understanding of the main focus of the different confusing notions.

The proposed framework can also be used to understand potential transitions of organizations aiming for service orientation. Service oriented organizations, as well as networked businesses, can position them in the proposed framework. Since the three proposed matrices address different aspects of a SODSC, there is a logical dependency between them. Based on this dependency, selection of a particular direction of service orientation at each aspect requires pursuing the same direction in the other aspects. We give three examples to clarify this dependency. First, organizations that based on their strategy are going to focus on customer intimacy as their main service-orientation theme [START_REF] Kaplan | The strategy-focused organization: How balanced scorecard companies thrive in the new business environment[END_REF], should be able to handle value networks through relational customer experience control, see the left top cell in the matrices proposed in Figure2, Figure3 and Figure 4. Second, organizations that focus on integrated product services delivery competences should be able to manage agile supply networks through demand-driven control, see the right bottom cell in the matrices proposed in Figure2, Figure3 and Figure 4. Third, innovation based organizations in the service-oriented context, willing to co-create new services to offer integrated solutions for customers, should be capable of managing a collaborative value network through customer-centric and demanddriven control, see the right top cell in the matrices proposed in Figure2, Figure3 and Figure 4.

Conclusion

In this paper, through a cybernetic system based representation of SODSC, the three main aspects of SODSC have been investigated, i.e. the service-oriented value aspect, the partnership aspect and the control aspect. This investigation has resulted in three two-dimensional matrices which form together an integrated framework to address the different SODSC notions and views in a structured way. This integrated framework enables to recognize different types of 'real-life' service orientation transitions. The paper also addresses the first steps towards a validation of the integrated framework, i.e. by illustrating and explaining service orientation transitions of three 'real-life' cases in the ICT industry.

Although the proposed integrated SODSC framework is based on literature research, analysis and logical reasoning, and the positioning of the real-life cases shows its usability, more case study research is recommended to validate, strengthen and enrich the framework.

Fig. 1 .

 1 Fig. 1. The cybernetic system based representation of SODSC aspects

2 -Fig. 2 .

 22 Fig. 2. The characterization of service-oriented value

Fig. 3 .

 3 Fig. 3. The characterization of the partnership aspect of SODSC

Fig. 4 .

 4 Fig. 4. The characterization of control aspect of SODSC


Jens Ziegler
email: jens.ziegler@tu-dresden.de

Robert Buchmann
email: rbuchmann@dke.univie.ac.at

Markus Graube
email: markus.graube@tu-dresden.de

Jan Hladik
email: jan.hladik@sap.com

Tobias Münch
email: tobias.muench@sap.com

Patricia Ortiz
email: portiz@innovalia.org

Johannes Pfeffer
email: johannes.pfeffer@tu-dresden.de

Florian Schneider
email: florian.schneider2@tu-dresden.de

Mikel Uriarte
email: muriarte@nextel.es

Dimitris Karagiannis

Leon Urbas
email: leon.urbas@tu-dresden.de

Implementation and Operation of Collaborative Manufacturing Networks

Keywords: Virtual enterprise, collaborative manufacturing network, mobile interaction, semantic data, co-operation, co-creation

Collaborative networks of manufacturers, suppliers and even customers are an emerging trend in global manufacturing. Higher flexibility, shorter time to market and economic as well as technological synergies create value and strengthen the market position of such virtual enterprises. The ComVantage framework already provides a sophisticated technical approach for dynamic collaborative manufacturing networks based on semantic data, mobile app orchestration, business process modelling and sophisticated access control. This article discusses the services and processes that are necessary to implement and operate a virtual enterprise using the ComVantage framework. It identifies services and service providers, and proposes an infrastructure and a tool environment for the ComVantage approach.

Introduction

In order to master the competition in a global market, companies do not only have to operate more efficiently, they further need to be much better cross-linked among each other. Moreover, agility in terms of networking and process execution is important [START_REF] Kim | A modeling framework for agile and interoperable virtual enterprises[END_REF]. The execution of business processes across organizational boundaries as well as crosslinking data sets of collaboration partners are key success factors and initiate the transformation of isolated individual companies towards an integrated, agile virtual enterprise. Resulting Collaborative Manufacturing Networks (CMN) may also include customers in order to leverage co-creation and co-production of customer-oriented products and services.

By definition of Barnett, et al. [START_REF] Barnett | An architecture for the virtual enterprise[END_REF], a virtual enterprise is based on a temporary alliance of several businesses. It takes advantage of a market opportunity and dissolves, when it has passed. A virtual enterprise does not have own major resources but consists of the resources and core competencies of the individual partners. The European research project ComVantage, which is funded by the European Commission within the Framework Programme No. 7, has the goal to develop a software architecture as well as a working prototype of a distributed infrastructure for virtual enterprises [START_REF] Muench | Collaboration and interoperability within a virtual enterprise applied in a visionary mobile maintenance scenario[END_REF].

From a business perspective, the most important question to be answered is which positive impacts on the business can be created with the implementation of a CMN based on the ComVantage infrastructure, and which additional expenses and dependencies must be taken into account on the opposite. Synergies during implementation may result from jointly used business services and the reuse of shared resources. Additional expenses may be incurred by the necessary provision and harmonization of data and services for the network as well as by coordinative work within the network. Most collaborative activities further create dependencies that must also be considered. In this paper, a process for the implementation and operation of a CMN is presented, which maximizes synergies, minimizes dependencies and clearly allocates and structures the necessary activities. The process thus minimizes business risk and ensures a structured design and operation of the network.

State of the Art

Having clarified a generalized definition of a virtual enterprise and its purposes, the interpretations and implementations of collaborative working environments are very heterogeneous Alone among publicly funded research projects, there are several projects in the field of co-operation and co-creation. The project ADVENTURE for example has the goal to create a framework that provides tools to combine factories in a pluggable way to manufacture a particular product which consists of a high number of components from different suppliers. Core element of the three layer architecture is the central 'Dashboard portal' as the user interface for all for monitoring and managing purposes [START_REF] Shamsuzzoha | Virtual enterprise architectural framework: collaboration for small and medium enterprises[END_REF]. GloNet as another example follows a service-oriented approach with a novel framework for automated software service composition in a complex multi-stakeholder service scenario for product life cycles. Therefore, they provide mechanisms to model or compose software services via business processes and combine them with the product. The resulting product model will become available in a 'Business Services Provision Space' via web services as product-related information and services during its life cycle [START_REF] Camarinha-Matos | Collaborative Business Scenarios in a Service-Enhanced Products Ecosystem[END_REF]. In contrast to product or service related virtual enterprises, BIVEE's Virtual Innovation Factory (VIF) focusses on an innovative co-creation space with an ultimate goal to transform existing production processes and organizations into new ones as a following step to the Open Innovation paradigm by Henry Chesbrough. Based on collaborative and social network tools the idea moves through a flexible life cycle, called 'Innovation Waves', allowing to cover the whole flow up to production [START_REF] Moreno | BIVEE Virtual Innovation Factory[END_REF].

A core aspect of a temporary virtual enterprise is their life cycle, which can be basically subdivided into the five phases of Initiation, Partner search, Process design, Execution and Dissolution as it was done by Shamsuzzoha and Helo [START_REF] Shamsuzzoha | Virtual enterprise architectural framework: collaboration for small and medium enterprises[END_REF]. Another common aspect is the usage of software for collaboration and communication to establish Collaborative Manufacturing Networks (CMN). They have an integrated endto-end Information and Communication Technology (ICT), formalized (business) models and a shared knowledge space, based on Web 2.0 technologies. Therefore, the network provides their partners a cloud based platform for overall operational processes, like security access control and communication, as well as certain software tools to align their own business processes, data and background systems within the shared processes and data in the CMN.

The ComVantage Framework

The ComVantage project aims at developing a software architecture and a technological foundation of generic enablers for operating a virtual enterprise. The project will provide means to evaluate the business impact and will prove the suitability of the approach in three different use cases. With respect to the challenges addressed in the introduction, the following key concepts characterize the ComVantage software architecture:

First, a decentralized approach is required in order to address the specific requirements of virtual enterprises. The ComVantage approach supports individual and local instances of a collaboration hub for each network partner. Figure 1 illustrates an exemplary CMN setup containing two partners. Each collaboration hub offers a Domain Access Server as single point of access to local datasets and a couple of local data sources. The decentralized collaboration hub concept enables each partner to keep full control about their valuable business data. Furthermore, the single point of access paradigm for each collaboration hub ensures that applications can be developed independently of specific data sources and are decoupled from their heterogeneous data models. SPARQL and JSON/RDF are used as standardized interface technology between all components of the architecture to achieve high interoperability and flexibility. However, collaboration partners are not forced to run and maintain their own infrastructure, but can use shared collaboration.

Second, semantic data harmonization based on RDF and Linked Data principles is used to realize the single point of access paradigm of the collaboration hub. Whereas data models (as ontologies) will be stored directly in RDF (in Triple Stores), legacy systems need to be integrated by the use of Linked Data adapters (see Figure 1). These adapters perform a mapping from legacy data (e.g. from a relational database model) to a uniform data model based on RDF for each collaboration hub. While the mappings will be defined at design-time, the extraction of data may occur at run-time in order to avoid the persistence of redundant semantic data that need to be kept in sync with the original legacy data. Additionally, a multi-tiered access control approach was developed. Cross-domain authentication, physical separation of data in views and SPARQL query rewriting based on role-driven policies ensure that unauthorized access in a setup of collaboration and inter-organizational access to information is prohibited.

Third, collaboration scenarios are driven by the execution of inter-organizational business processes to realize a cross-domain product value chain. Especially in the manufacturing industry, business processes may be very complex. On the other side, the personnel on the shop floor needs intuitive and usable mobile IT support. ComVantage has developed the Industrial App Framework that allows the orchestration of limited-purpose mobile apps to App Ensembles which support complex and interorganizational workflows. A pool of Generic Apps can be used to accelerate the user interface development. These Generic Apps can be adapted to specific use cases and automatically orchestrated to App Ensembles using a business process model.

Implementation and Operation of a ComVantage Network

Overall Process

In general, implementation sub-processes are categorized into collaborative processes where all partners have to jointly create a common result, shared processes that are done by an internal or external provider for all partners, and company internal processes that have to be done by each partner individually. Collaborative processes require coordinated work and joint decisions by all partners. Shared processes are equal for all partners and thus have only to be done once. The results can be shared resources or services. Company internal processes do not require collaboration. The results feed into the CMN. It is obvious that company internal processes can also be outsourced. However, the main difference to shared processes is that there are no synergy effects besides the joint use of (external) competencies.

The ComVantage overall implementation process consists of seven sub-processes, which are done sequentially in three phases. In the first phase, the common business processes (BPM) and roles (RM) are modeled. These are collaborative sub-processes, where joint decisions must be made. In the second phase, ontologies and apps are developed that are necessary to implement the BPM and RM. These are shared processes whose results are shared by all partners. In the third phase, each partner provides datasets for the developed ontologies and creates an Access Control Model (ACM) based on the RM to secure the provided data. In parallel, app ensembles are orchestrated based on the BPM, ontologies and apps. The app ensembles provide the datasets to authorized users according to the underlying BPM and are thus the final result of the entire process. All sub-processes are scalable. Individual activities may be omitted and the tools may be selected according to the actual requirements.

Role Modelling and Business Process Modelling

The Business Process Modelling phase is traditionally tightly coupled with Role Modelling. For the hereby presented approach it is essential that role assignments use machine-readable representations so that the semantic relation between a process task and its performing role is preserved beyond the modelling phase, for example through a model serialization. To achieve this, the ComVantage approach relies on a metamodelling platform [START_REF]ADOxx tool[END_REF] and an RDF serialization vocabulary discussed in more detail in [START_REF] Buchmann | Conceptual modeling for mobile maintenance: the ComVantage case[END_REF], with a proof-of-concept collaborative modelling tool hosted by the Open Model Initiative [START_REF]The Open Model Initiative Laboratory -the ComVantage modeling prototype page[END_REF]. The modelling tool implements the iteratively evolving ComVantage modelling method, whose meta-model specifies the semantic links that can be created by modelers (usually as inter-model hyperlinks) and can be externalized for RDF queries in order to enable the later phases of the ComVantage implementation process (e.g. App Orchestration).

Business process modelling is a well-established approach, however there is a diversity of tools and languages to support it -some of them coming from standards, others from commercial tools. Popular approaches aim at high reusability across domains, therefore high abstraction levels that do not retain any domain specificity and are not prepared to collect requirements. The ComVantage approach provides the possibility of assigning, to each process task, domain specific resources and artefacts: mobile apps requirements, robots, product parts etc. Therefore, the meta-model underlying the business process modelling phase integrates with explicit associations the following facets: a) Process motivators (the trigger of a virtual enterprise -a customized product order, a service, a temporary market opportunity); b) Processes (the actual control flows triggered by the process motivators and possible acting upon them -the case of production processes); c) Process participants (liable entities or assets). In this last class, there are business or individual roles (liable entities described as a business network or organizational chart), required mobile apps (with functional capabilities) and access means (queries indicating the kind of access and endpoint required to perform a process task). Each task of a business process model can be explicitly linked to all these types of participants, hence enabling the collection of requirements around each specific process (by querying the process model serialization). These requirements can feed into the App Orchestration and Access Control phases in the following ways. First, App Orchestration deployments can read the Diagrammatic Orchestration Model -a usage precedence graph describing which apps are required for a selected role, and in which order. This model is derived automatically from the business process model by graph transformation means (details in [START_REF] Buchmann | Conceptual modeling for mobile maintenance: the ComVantage case[END_REF]). Second, the Access Control phase can collect the queries assigned to process tasks -they are queries that should be enabled by the policies of endpoint owners, for the specific roles linked to the same tasks.

Ontology Engineering

In order to design the ontologies that serve as terminologies and data structures for the applications, several ontology engineering methodologies [START_REF] Fernandez-Lopez | METHONTOLOGY: from Ontological Art towards Ontological Engineering[END_REF][START_REF] Grüninger | Methodology for the design and evaluation of ontologies[END_REF][START_REF] Lopez | Overview of Methodologies for Building Ontologies[END_REF][START_REF] Pinto | Ontologies: How can They be Built?[END_REF] were considered, and the Enterprise methodology developed by Uschold and King [START_REF] Uschold | Building Ontologies: Towards a Unified Methodology[END_REF] was selected, since it provides sufficient guidance to provide the ontology engineers with a clear process without requiring disproportional overhead. This methodology suggests the following phases: 1. Identifying the purpose; 2. Building the ontology, with steps a) Capturing, b) Coding, and c) Integrating existing ontologies; 3. Evaluation; 4. Documentation.

The first step can essentially be completed before the start of the CMN and laid out in the business plan. For step 2a, interviews with domain experts from the application partners have to be conducted to determine the essential terms of the corresponding domain and their relations. Step 2b can be performed with the help of the Protégé tool, generating RDFS or OWL ontologies based upon these terms. In order to integrate existing ontologies (step 2c), terms from popular ontologies are used where this is possible, e.g. the FOAF and vCard ontologies describing persons and their addresses or the GoodRelations ontology for prices and other costs. Links to DBpedia entities should also be included if appropriate. Step 3 involves using the developed ontologies within the respective application areas and evaluating them with respect to usability, clarity, and consistency. The final step is performed by documenting the developed ontologies in text documents and by using the rdfs:label and rdfs:comment properties within the ontologies themselves. In order to also enable non-experts to perform basic ontology operations, the OntoSketch tool [START_REF] Brade | OntoSketch: Towards digital sketching as a tool for creating and extending ontologies for non-experts[END_REF] was developed, which allows for refining existing ontologies by domain experts using a graphical editor.

App Engineering

During the App Engineering phase (illustrated in Figure 5) the set of apps required for the network's business processes is created. If an app repository already exists it is first checked for apps that can potentially be reused in the business processes. Then, existing conventional apps, e.g. document viewers or messaging applications, are identified in order to integrate them during the subsequent App Orchestration phase. For all other app requests in the business processes, such as specialized data views or tasks that manipulate the Linked Data graph, new apps may be developed.

Any app that shall be used must be formally described in the developed App Description Language (ADL). The ADL is a domain specific ontology for modeling an app's characteristics essential for collaboration.

Besides conventional meta-data such as operating systems, supported screen sizes, languages, etc., the ADL supports modeling the app's abilities, input and output data, and entry points. The entry points are essential for forming an app network, the modeled inputs and outputs allow for interapp-communication. The abilities are later used to match apps to activities in a business process model.

Linked Data Provisioning

The main task of the Linked Data Provisioning phase (illustrated in Figure 6) is to generate, distribute and supply the CMN with the information necessary for the common business models. Sources of information can be, among others, Excel sheets, XML files, and proprietary engineering or control systems. The information has to be modeled with the approved ontologies in order to be useful for the CMN.

The Ontology Engineering phase delivers the meta-models of the information which is necessary for the shared business cases. Afterwards, the sources of this information (existing legacy systems or already Linked Data stores) can be identified. Linked Data adapters may be provided for this data if this information is not already present as Linked Data. The adapters use the approved ontologies from the Ontology Engineering phase to transfer the legacy data into Linked Data taking domain specific knowledge into account. If the update rate of the legacy data is rather low, simple automated model transformations can be applied which provide a RDF output for an information entity as input (e.g. a single Excel file). Various frameworks (e.g. Jena for RDF support) and application interfaces (e.g. Enterprise Server for Comos) may support this task. The RDF file is then stored in a triple store (e.g. Virtuoso) which offers access via SPARQL. If the update rate of the data is rather high (e.g. the provision of process values), a service may provide direct access to the necessary information as Linked Data. Some dynamic adapters provide a local SPARQL endpoint (e.g. XLWrap, D2RQ) whereas others only provide data via a REST web interface as Linked Data.

Usually, the majority of the data provided by the partners is only loosely coupled. Hence, a link discovery and generation process between different datasets may generate additional links, which will also be stored in the Linked Enterprise Data cloud. A final validation of the RDF datasets is mandatory to ensure the reliability of the information provided in the cloud. This step can be done with tools, which may perform a RDF validity check, check the instances against the used ontology or common best practices, or even check against specific defined rules. Finally, collaboration networks need information about available datasets, their structure and content. Therefore, documentation is added to all datasets, which itself can be modeled as Linked Data by using for example the VoiD vocabulary.

Access Control

The main aim of the Access Control phase is to create an Access Control Model (ACM) based on the roles modeled (RM) to secure the information published as Linked Data. For the provisioning of trust, the ComVantage approach complements traditional XACML role-based multi-domain access control models, including SAML authentication, which are useful to control the access to dynamically changing Linked Data information, with innovative SPARQL query rewriting capabilities based on data views to address the security needs of mobile inter-organizational information sharing. The goal of the SPARQL rewriting process is to create queries that return the same results as the original queries except for those answers that contain restricted information. For this purpose, the security framework includes conditions to the original SPARQL query so that all the information requested is included within the set of information that the user is authorized to access taking into account its role, which has previously been modeled as explained in Section 4.2. In order to achieve this objective, this SPARQL rewriting process relies on the organization of the original RDF data in a set of Views with different access types (canSee or canUse) for the different user roles (see Figure 7).

The ComVantage security approach does not just guarantee that the access to the information remains secure, but it also has to ensure that the information published as Linked Data is just modified and updated by the users that are authorized to these tasks. For that purpose, SPARUL templates previously approved by the data owner are assigned to different user roles who will be allowed to modify and update the original Linked Data and the defined data views accordingly.

App Orchestration

The App Orchestration phase shown in Figure 8 takes results from the Business Process Modeling phase, the Ontology Engineering phase and App Engineering phase and leverages them to create App Ensembles that are used to view and operate essential aspects of the CMN (details in [START_REF] Ziegler | Beyond app-chaining: Mobile app orchestration for efficient model driven software generation[END_REF]). They constitute the network's front end and provide means to view and manipulate the information contained in its Linked Data graph. App Ensembles are sets of Apps that are interconnected in a meaningful way to fulfill mobile support requests in business processes. They facilitate the correct switching between apps and automate the exchange of information between them. To create an App Ensemble, appropriate apps for the business process must be selected from a repository. This is accomplished by comparing requirements stated in the Diagrammatic Orchestration model (which is derived from a business process) to the app's abilities formalized in their respective App Descriptions (using the ADL). Then the apps are adapted to the data structure of the CMN. This is accomplished by assigning SPARQL templates to the apps which adhere to the networks ontologies. SPARQL templates are SPARQL queries with placeholders that fit the network's information structure and provide necessary data to the apps. Using SPARUL the templates are also employed to manipulate the Linked Data graph. In the third step, connections between the apps are established by analyzing their entry points defined in the App Descriptions. The information from the three orchestration steps is joined into a Semantic Orchestration Model and serialized as RDF. Installable binaries of all Orchestrated Apps together with the generated Semantic Orchestration Model form an App Ensemble. It is deployed to a mobile device where it can be loaded and executed using the ComVantage App Management Component that interprets the Semantic Orchestration Model.

Progress beyond the State of the Art

Both technologically and administratively, the ComVantage approach addresses the challenge to generate a verified added value through the CMN early and with scalable effort. This takes into account that CMN may differ significantly in terms of size and composition, and in terms of its business objectives. The process has therefore been designed to generate as few dependencies between the partners of the CMN and resolve necessary dependencies as early as possible. Thus, the implementation costs and risks are minimized. On the other hand, the process achieves maximum synergy in joint activities. It is clearly defined which results can be reused and what activities can be outsourced to service providers. Moreover, the process is scalable. Activities can be omitted if not required, tools can be selected depending on the actual requirements of the CMN. Finally, the presented process is iterative. Since the implementation of a new CMN and the modification of existing CMN are based on the same process, the CMN can be continuously adapted to the current requirements.

The presented process has been implemented and validated in the context of three use cases in the areas of commissioning of production lines, customer-oriented production and maintenance of process plants. Both the composition and size of the CMN (from micro-company to large enterprises, including customers) as well as its business objective (acceleration of engineering processes, maximization of customerorientation, and optimization of operation and maintenance) have been varied across the use cases. It has been found that the presented process scales well with respect to both factors. At the same time it became apparent that the flexible use of manifold tools was arduous. Also, some activities were not yet sufficiently supported by appropriate tools. A (modular) integration of the proposed tools in an integrated development environment (IDE) and the development of appropriate tools should therefore be a focus for future activities.

Conclusion

In this paper, the processes, tools and outcomes have been presented that are necessary to implement a ComVantage collaborative manufacturing network (CMN). It has been shown that the overall process strives for minimization of dependencies, maximization of synergies and great scalability of all sub processes. In the next phase of the project, suitable integrated engineering tools will be designed to better support the processes described in this paper. These tools will be directly built upon the technologies and concepts of the ComVantage framework and thus promote the feasibility of the ComVantage approach to CMN in industry and business.

Figure 1 .

 1 Figure 1. The big picture -Exemplary setup of a CMN with two partners and ICT infrastructure including mobile apps, collaboration hubs and data sources.

Figure 2 .

 2 Figure 2. Seven Steps towards a CMN -The ComVantage implementation process.

Figure 3 .

 3 Figure 3. Role Modelling and Business Process Modelling. Activities may be manual or automated. Data may be formatted as Linked data (orange) or not (white). Input and output of the entire process marked with arrows.

Figure 4 .

 4 Figure 4. Describe the domain -Ontology Engineering.

Figure 5 .

 5 Figure 5. App Engineering.

Figure 6 .

 6 Figure 6. Breathe life into the CMN -Linked Data Provisioning.

Figure 7 .

 7 Figure 7. Secure the Linked Enterprise Data -Establishing Access Control.

Figure 8 .

 8 Figure 8. Bring it to the users -App Orchestration.

Acknowledgments.

The research leading to these results was partially funded by the European Community's Seventh Framework Programme under grant agreement no. FP7-284928 ComVantage.


Bernhard Kölmel
email: bernhard.koelmel@hs-pforzheim.de

Rebecca Bulander
email: rebecca.bulander@hs-pforzheim.de

Uwe Dittmann
email: uwe.dittmann@hs-pforzheim.de

Alfred Schätter
email: alfred.shaetter@hs-pforzheim.de

Günther Würtz
email: guenther.wuertz@steinbeis.de

Usability Requirements for complex Cyber-Physical Systems in a Totally Networked World

Keywords: Cyber-physical systems, Usability, a best practice process model

 In this paper we define CPS and highlight the importance of usability for CPS. Then we describe two different cases and provide different methods how to improve the usability of CPS.

Cyber-Physical Systems

Baheti and Gill define CPS as Systems that integrate the cyber world with the physical world. The computational and physical components of such systems are highly interconnected and coordinated to work effectively together, sometimes with humans in the loop. [START_REF] Baheti | Cyber-physical Systems[END_REF]"Cyber Physical Systems (CPS) are integrations of computation with physical processes. Embedded computers and networks monitor and control the physical processes, usually with feedback loops where physical processes affect computations and vice versa." [START_REF] Lee | High-Confidence Medical Device Software and Systems[END_REF] CPS will also contribute to safety, efficiency, comfort and human health. Therefore, it helps to solve some key challenges of our society such as the ageing population, limited resources, mobility, or the shift towards renewable energies, which were caused by the demographic transitions and globalized world. [5] "The promise of CPS is pushed by several recent trends: the proliferation of lowcost and increased-capability sensors of increasingly smaller form factor. The availability of low-cost, low-power but with high-capacity [...] and the wireless communication revolution […] continuing improvements in energy capacity, alternative energy sources and energy harvesting. The need for CPS technologies is also being pulled by CPS vendors in sectors like aerospace, environmental control, […] factory automation and healthcare who are increasingly finding that the technology […] is seriously lacking." [START_REF] Rajkumar | Cyber Physical Systems: The Next Computing Revolution[END_REF] About 98 percent of the microprocessors nowadays are working embedded, connected via sensors with the outside world. They are increasingly networked with each other in the Internet. The physical world merges with the virtual world, the cyberspace. [START_REF] Acatech | acatech[END_REF]"A large variety of collaborative networks have emerged during the last years as a result of the challenges faced by both the business and scientific worlds. Advanced and highly integrated supply chains, virtual enterprises, virtual organizations, professional virtual communities, value constellations, and collaborative virtual laboratories, represent only the tip of a major trend in which enterprises and professionals seek complementarities and joint activities to allow them participate in competitive business opportunities." [START_REF] Camarinha-Matos | Targeting major new trends, in Collaborative Networked Organizations -A research agenda for emerging business models[END_REF] CPS extend the notion of these collaborative networks by the integration of physical nodes and their virtual representation as specific entities within collaborative networks.

The trends push CPS to perform well and be useful in the mentioned areas. People and the industry want to have user-friendly devices which are not only handy but also have great appearances with high performance as well as capacity and of course with lower prices. The demand of using CPS is pulled by several industries and that is why CPS is always being developed in the application areas such as industry 4.0, automotive and avionic industries, logistics structures and other engineering fields where CPS has a valuable contribution. [START_REF] Rajkumar | Cyber Physical Systems: The Next Computing Revolution[END_REF] Another essential argument about achieving the goals is to link human intelligence with computer power, set by Lanz and Torvinen as follows: "The real operating environment is not stable or predictably behaving. Systems in all fields have become parts of bigger systems via cooperation and communication within each other […] In order to operate in such dynamic and complex environment best of the both worlds; human intelligence and computers' computing power needs to be utilized in right places." [START_REF] Lanz | Social Media in Manufacturing -Just hype or concrete benefits?[END_REF] "Cyber physical systems research aims to integrate knowledge and engineering principles across the computational and engineering disciplines (networking, control, software, human interaction, learning theory, as well as electrical, mechanical, chemical, biomedical, material science, and other engineering disciplines) to develop new CPS science and supporting technology." [START_REF] Baheti | Cyber-physical Systems[END_REF] The rapid research and technological advances in Internet of Things and increasing availability of sensors, actuators, and mobile devices have created an exciting new ubiquitous computing paradigm as an emerging paradigm is changing the way we live and work today. Via a ubiquitous infrastructure consisting of a variety of global and localized networks, users, sensors, devices, systems and applications may seamlessly interact with each other and even the physical world in unprecedented ways. To realize this usable and trustworthy computing that delivers secure, private, and reliable support for interconnected systems (i.e. organizations, services, objects) usability plays a pivotal role. [START_REF]SUTC2008. IEEE Conference[END_REF] 2 Usability of Complex Technical Systems "Usability is the ease of use and learnability of a human-made object. The object of use can be a software application, website, book, tool, machine, process, or anything a human interacts with." [START_REF] Gerson | e-Study Guide for: Technical Communication: Process and Product[END_REF] Nonetheless not only usability is a crucial point of interaction of humans with technical and cyber-physical systems in the virtual world but trust and reliability is also a major issue to be considered. " […] designing predictable and reliable components makes it easier to assemble these components into predictable and reliable systems. But no component is perfectly reliable, and the physical environment will manage to foil predictability by presenting unexpected conditions." Especially in quite complex and critical environments like cyber-physical systems sometimes are trust and reliability becomes very important.

Technical complexity refers to either the fundamental interaction characteristics (input and output) of the technology being complex, or where the underlying system architecture is complex, linking a variety of different systems, architectures, agents, databases, or devices. [START_REF] Golightly | Novel Interaction Styles, Complex Working Contexts, and the Role of Usability[END_REF] At some point a decision must be made regarding the system interaction approach that is made towards the user. While issues of technical complexity have been discussed for many years, the rapid pace of change in disruptive technology domains means we are now required to design for a whole new range of cyber-physical systems that are emerging into common use and demand the development of new interaction styles and new guidelines.

Contextual complexity includes the broader tasks, roles, or jobs the technology is proposed to support, especially when tasks are open-ended or unstructured. A welldesigned system will consider this more contextually complex type of scenario when developing a system, to ensure that the appropriate information required to support these contextual goals is incorporated into the system.

One implication of the need to reflect both technical and contextual complexity in design is an emphasis on multiple methods. While laboratory and quantitative work still has an important part to play, most often addressing the issues of technical complexity, qualitative methods such as ethnography, interviews and content analysis, and detailed observation are also vital for capturing the factors that contribute to contextual complexity. In practice, we find that methods need to be used in combination so that all aspects of usability can be addressed.

Case Studies

Based on this, we present examples from our work in two specific domains that encompass both technical and, in particular, contextual complexity. We concentrate on considering the applicability of methods in complex situations.

The first example is a case, where security tokens connected to machines guarantee that only official products are produced, where the challenge of design and evaluation is being able to effectively create intercultural systems, and capture the contextual characteristics of real and virtual working environments.

The second domain is energy efficiency management in large connected environments, where the variety of inputs and outputs, the challenge of working with traditionally disconnected domains, and the lack of design guidelines or standards pose challenges for the usability experts.

Domain Production Energy Case description

Security tokens connected to machines guarantee that only official products are produced Energy efficiency management in large connected environments with variable inputs and outputs Technical complexity e. g. managing of different security tokens e. g. balancing of energy; connection of different environments; managing the variable inputs and outputs Contextual complexity e. g. producing customer individual productions using different (customer) context e. g. management of priorities of inputs and outputs, if there might be a higher need of energy

Usability

Using different methods to improve the usability:

• Using cost-efficient and field-tested concepts • Repetitive and detailed model (also for customer specific projects) • Clearly specified process using an accepted framework and process model based on standards • Testing of products and processes using defined criteria • Considering always both sides: vendor and users • Etc. Table 1

: Case Studies

The cases demonstrate two points: They illustrate the importance of both technical and contextual complexity in different technology contexts and they provide example methods that can be applied to examine the human factor issues associated with complex usability. Because of the inherent complexity, it is often necessary to use multiple methods in combination.

Complexity takes on both a technical and contextual dimension. A number of methods are considered, and across both case domains there is an importance on using multiple methods to address usability, there is no one single method that can be used to ensure usability and this is particularly apparent in cases of usability of cyberphysical systems. Because complexity may exist from a number of different sources, it is necessary to sometimes use different approaches to unravel all the various issues that might lie within (see also table 1).

The various methods have its own strengths and weaknesses. Qualitative interviews are open to subjectivity on the part of the usability specialist, whereas more quantitative work is only as valuable as the reliability and validity of the data being collected. Using a number of methods can improve accuracy and enables us to build a fuller understanding of the critical issues.

Summary and Conclusions

CPS connect the cyber world with the physical world. The cyber and physical components of these systems are strongly coordinated to work effectively with humans in the loop. [START_REF] Baheti | Cyber-physical Systems[END_REF] The rapid deployment of CPS leads to more and more interactions between human and the networked world. Usability, reliability, trust and security are the important key issues for the CPS success. The ability to interact with, and expand the capabilities of the physical world through computation, communication, and control is a key enabler for future technology developments. [START_REF] Baheti | Cyber-physical Systems[END_REF] In this domain complex usability has two dimensions, a technical and a contextual dimension. The two are interdependent, and both are of high importance to usability specialists and the successful implementation of systems that are relevant to complex usability. It is unlikely that a single method will be sufficient to capture all aspects of technical and contextual usability. If methods are used in combination across the different aspects of complexity, then there is a possibility to identify critical issues to address them. There is a need to ensure that new methods are generalizable across applications or domains and new methods must acknowledge both the technical and contextual complexity of systems. This makes it necessary to have a toolbox from which users can select tools appropriate to the complex usability issues that they encounter.