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Procedía CIRP 16 (2014) 146 - 151
Product Services Systems and Value Creation. Proceedings of the 6th CIRP Conference on Industrial
Product-Service Systems
Interaction within Dynamic IPS2 Networks - A Proposal of an IPS2 Lifecycle Management and IPS2 Delivery Management Architecture
Thomas M. Dorkaa'*'**, Hoang Bao Dangb'**, Horst Meiera, Michael Abramovicib
aRuhr-Universität Bochum, Chair of Production Systems Universitätsstraße 150, 44801 Bochum, Germany bRuhr-Universität Bochum, Chair of IT in Mechanical Engineering (ITM) Universitätsstraße 150, 44801 Bochum, Germany
* Corresponding author. Tel.: +49 (234) 32-28925; fax: +49 (234) 32-08925. E-mail address: dorka@lps.ruhr-uni-bochum.de: ** Both authors contributed equally to this work.
Abstract
In the delivery of Industrial Product-Service Systems (IPS2), a dynamic network of partners is involved. To deliver and use IPS2 efficiently, the IPS2 has to be managed from several heterogeneous perspectives, namely from a strategic, inter-organizational, operational and information perspective. To manage the information exchange between the partners, an architecture that supports the interaction between the perspectives and their corresponding software systems is needed. This paper introduces the different management perspectives of IPS2 and their interplay. For the information exchange, an architectural approach is presented and implemented within a conceptual scenario situated in the micro milling industry. Especially the web service-based interaction between an IPS2-Lifecycle Management System (IPS2-LMS) and an IPS2-Execution System (IPS2-ES) is described in detail.
© 2014 ElsevierB.V. Thisis an open accessarticle under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).
Selectionandpeer-reviewunder responsibilityof thelnternationalScientific Committee of "The 6th CIRP Conference on Industrial Product-Service Systems" in the person of the Conference Chair Professor Hoda ElMaraghy" Keywords: Industrial Product-Service Systems (IPS2); IPS2-Lifecycle Management; IPS2-Execution System
1. Introduction
Industrial Product-Service Systems (IPS2) are new customer-specific solutions for business-to-business markets and can be viewed as an integrated bundle of key industrial goods as well as corresponding services and software [1]. In order to develop, provide and use such solutions, cross-linked information related to all domains (e.g. mechanics, electronics, service, software) is needed. Furthermore, different partners within the IPS2 networks are involved throughout the lifecycle of the IPS2. Some of them may be part of the partner network right from the start while others join in at later points [2]. This poses the challenge to exchange and manage IPS2-related information. All partners have to be supplied with relevant information and their systems have to be integrated accordingly, so that information can be
managed, gathered and exchanged efficiently within a dynamic IPS2 network.
During the IPS2 delivery, the IPS2 provider has to manage the dynamic IPS2 delivery networks and execute strategic capacity as well as operational resource planning. By doing so, the resources of the partners in the network organization are assigned to the different tasks needed for the provision of the IPS2. Whenever a partner enters or leaves the network, these changes have to be reflected in the delivery plan. Furthermore, newly arising demands during the operation of IPS2 require an immediate reaction by the IPS2 provider. These demands mainly consist of two categories: On the one hand, unplanned demands can occur, e.g. caused by malfunctioning components that require the scheduling of a repair process. On the other hand, planned demands are induced by scheduled IPS2 solution alterations that may be
2212-8271 © 2014 Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).
Selection and peer-review under responsibility of the International Scientific Committee of "The 6th CIRP Conference on Industrial Product-Service Systems" in the person of the Conference Chair Professor Hoda ElMaraghy" doi: 10.1016/j .procir.2014.01.002
caused by either varying customer needs, a modified business model or a changed delivery environment.
Mastering the aforementioned requirements and challenges is a key success factor in order to deliver complex and customer-specific IPS2 solutions. It enables the IPS2 supplier to provide the customer value that has been defined in the stipulated business model.
This article describes the IPS2 management from different perspectives and presents the interplay of some of the key concepts supporting the IPS2 supplier in managing the IPS2 throughout the lifecycle. More specifically, the IPS2 lifecycle management has been developed to manage and integrate domain-specific information, offering a central information platform for different partners of the IPS2 network. It provides IPS2-relevant information (e.g. regarding requirements for service delivery) to the central IPS2-Execution System (IPS2-ES), which organizes and plans the resources needed in the service delivery for all IPS2. In return, the IPS2-ES informs the lifecycle management system about the allocation of resources (e.g. employees and tools assigned to a specific service delivery). This information enables the lifecycle management system to provide task-specific information to the employee. A web service-based interface enables an effective mutual exchange of information between these systems. Moreover, in order to illustrate the intensive interaction in a dynamic environment between the above-mentioned key concepts, a scenario has been developed and validated in a conceptual case study in the field of industrial micro-production technology.
2. Related works
resources and provide flexibility and individual solutions in the organization of processes while leaving existing organizational structures in the partners' company unchanged. Based on the provider network, an IPS2 network for each IPS2 is created. The IPS2 networks are a combination of different virtual organization units that are responsible for the delivery of the associated IPS2. Whenever a specific delivery process has to be executed, e.g. a maintenance or repair, the partners of the IPS2 network assigned to this task form a temporary IPS2 delivery network for the time of the delivery. [8]
Strategic and operational planning methods are used to determine which network partners have to execute which delivery processes [9]. As the planning cannot be performed manually, a software system is needed to support the IPS2 provider. This system is called IPS2-Execution System (IPS2-ES) and connects all the partners' software systems to receive the necessary data to perform the process scheduling [10]. It is defined by [11] as follows:
"An IPS2-Execution System is the essential software system for the IPS2 operation phase that supports the IPS2 provider in the provision of customer value by adaptive IPS2 delivery planning, IPS2 network management and an integrated performance measurement method."
The IPS2-ES works together with the IPS2-Control System (IPS2-CS, [12]) to ensure the reliable delivery of customer value to the IPS2 customer. By monitoring each IPS2 and its delivery, the IPS2-CS is able to communicate arising demands to the IPS2-ES, which in turn can schedule the necessary delivery processes. A more detailed description of the interaction of both systems can be found in [13].
Real PSS (PSS Instances) ^^^^ Operation End of Life
^ p ^ -Product : Service (7 "p^s'1;^ : Industrial Product-Service System
Fig.1. IPS2 lifecycle phases
In contrast to selling products and services separately, IPS2 are a way of providing customer value by integrating product and service shares [3], [4]. A definition of IPS2 is given in [5] as follows:
"An Industrial Product-Service System is characterized by the integrated and mutually determined planning, development, provision and use of product and service shares including its immanent software components in Business-to-Business applications and represents a knowledge-intensive socio-technical system."
IPS2 are an offering that give the IPS2 provider the possibility to maintain a life-cycle-spanning contact with his customers [1]. This includes the phases of planning, development, implementation, operation (also known as delivery and use) and closure [6] (see Fig. 1).
Especially the development and the delivery of IPS2 are complex tasks requiring knowledge and expertise in several distinct fields. Therefore, a network of partners is formed, consisting of the IPS2 provider, third-party suppliers as resource and knowledge providers (e.g. spare parts, service technicians, developers) and the IPS2 customer [7], [8].
The IPS2 network is responsible for the IPS2 throughout its lifecycle and is characterized by the dynamic changing of network partners [2]. All partners are collaborating in the so-called provider network. Instead of participating as a whole, each partner is represented by one or more virtual organization units. The units consist of technical and human
Throughout the lifecycle of IPS2, the data of virtual and real PSS from the IPS2 provider and also from cooperation partners as well as from the customer need to be managed. This IPS2-related information has to be available for all actors within the IPS2 network in order to plan, develop, use or provide IPS2.
Over the last decade, Product Lifecycle Management (PLM) has become the central management approach of engineering processes and data, and it has been used as a company-wide integration platform. Current PLM solutions are mainly focusing on the management of goods-related data and engineering processes within the development phase. Different research is still done to extend the PLM approach to cover after-sale phases like the closed loop PLM approach [14], [15], [16] but without taking into account the management of service components and the interplay aspects between goods and services. In order to integrate the engineering of goods and services and to manage all IPS2-related data throughout the lifecycle, an overall lifecycle management approach for IPS2 has been developed [17] and
prototypically implemented [18]. Besides merely handling product-and-service-related data and processes, the PLM approach for IPS2 (IPS2-LM) also considers the interdependencies of information and communication between all of the partners and customers involved in the IPS2 lifecycle.
3. Different Management Perspectives on IPS2 with an overarching IT landscape architecture
IPS2 can be described as having four key management perspectives (see Fig. 2): At first, the strategic perspective refers to the business model which has been agreed upon by the IPS2 provider and the customer. It includes the prevailing aims of the IPS2, e.g. the guaranteed availability or provision of a specific function. From the inter-organizational perspective, the delivery of the IPS2 is planned. It involves the complex task of managing the resources of all network partners (e.g. workers, tools, etc.). In order to ensure a reliable IPS2 delivery, the required resources have to be planned in advance, distributing them at the right time, at the right place and of the right quality. In order to ensure a smooth and efficient planning of an IPS2 delivery, which also has to take the aims of the IPS2 into account, real-time information management within the IPS2 network is essential. Communication between the network partners needs to be managed on an easily accessible common platform, which allows real-time reaction to the highly dynamic changes occurring during the IPS2 lifecycle. Finally, the operational perspective refers to the actual delivery of the IPS2, as planned by the inter-organizational perspective, governed by the strategic aims, and provided with the needed knowledge from the information perspective. This brief description already demonstrates that all of the IPS2 key perspectives are interrelated and closely linked with each other. Due to the dynamic and complex nature of the IPS2, agent systems supporting the monitoring and controlling of the IPS2 delivery (operational perspective) are essential for an efficient management of the IPS2.
\ Strategic Perspective
/Operational Perspective"
within the IPS2 network is a prerequisite for a smooth interaction between all network partners and real-time monitoring of the IPS2. Until now, systems supporting one of the key perspectives of IPS2 management have been developed separately. For example, the IPS2-ES supports the planning of the IPS2 delivery (inter-organizational perspective) while the IPS2-LMS represents the information perspective. However, for a fluent and efficient overall management of the IPS2, an integration of these systems is needed.
To provide the required interaction between the diverse software systems from different perspectives, a common system architecture has to be established which allows for dynamic changes in the IPS2 network while ensuring solid data exchange. In software engineering, there are several types of architectures. Among these are service-oriented [19], plug-in [20] and component-based architectures [21]. While each single software system from the varying domain-specific and partner-specific IT-landscapes may utilize its own architectural style, the common architecture has to connect all these heterogeneous systems. Therefore, different interfaces have to be established. A list of requirements is given in table 1, which also shows how the different architectural approaches fulfill these requirements.
Table 1. Fulfillment of Requirements by different System Architectures
Architecture
Requirement
Component- Plug-in-
R1. Flexibility
R1.1 Adaptable to dynamic IT landscapes
R1.2 Adaptable to heterogeneous IT environments
R1.3 No system downtime caused by changes
R1.4 Orchestration and management of processes
R1.5 Instant modification of automated business processes
R2. Sustainability
R2.1 Software usable for other
independent software system
R2.2 Backwards compatibility
R3. Implementation
R3.1 Low implementation effort for interfaces
R3.2 Programming language independent
Communication
R4. Integration
R4.1 System and platform independent
Fig.2. Different management perspectives of IPS2 (own illustration)
However, not all reactions required to ensure a reliable IPS2 delivery can be taken onto the operational level. Hence, some regulatory measures have to be taken from the inter-organizational perspective, making an interaction between these perspectives mandatory. Automated communication
R4.2 Reliable and scalable
R4.3 Conforms to enterprise standards
R4.4 Easily testable
A component-based architecture is not suitable for the described dynamic IT-landscape (R1.1). While the
architecture conforms to enterprise standards (R4.3) and is easily testable (R4.4), the different components and the interfaces between them would have to be defined at an early stage before the buildup of the IT-landscape (R1.5). All partners would have to be identified beforehand and their software systems would have to be prepared to serve as a component in the architecture (R1.2). Furthermore, a change in the IT-landscape or in the provider network as well as in the business processes would result in a modification of the component architecture, which has to be newly defined and constructed (R1.4).
In contrast to the component-based approach, a plug-in architecture would provide more flexibility (R1.1, R1.2). Plug-ins can be added to or removed from the system at any time, however, a failure of the base plug-in system would result in a breakdown of the whole constructed system (R1.3). Furthermore, most plug-in systems make use of language-specific programming (R3.2), which would imply a high effort supporting the plug-in approach in partner-specific applications.
A service-oriented architecture (SOA) does not necessarily have the limitations described above. By using a loose coupling between interfaces, only the required interfaces are established and can be used independently of other systems and interfaces. A change of the system or the interfaces only affects applications or services which are already in use.
Web services have proven to be a simple, yet powerful approach to connect software systems over a network [22]. Web services are platform-independent (R4.1) and can be created and used with virtually any programming language (R3.2) in any application (R1.2). Hence, a service-oriented IT-landscape architecture using web services is an appropriate solution (see Fig. 3).
(R1.5). Existing IT investments of different partners within the cooperation network can be used in conjunction with SOA (R2.1) so that new investments in IT resources are unnecessary. In addition, services specified by different partner systems for certain requirements can be reused and combined based on business needs (R1.4). The integration of heterogeneous systems within the IPS2 network can be achieved easily by specifying needed services instead of implementing interfaces (R1.2). Thus, an SOA fulfills all defined requirements concerning flexibility, sustainability, implementation and integration (see table 1).
4. Prototypical Implementation and Validation
The proposed interaction between IPS2 lifecycle management and IPS2 delivery management has been implemented and verified in a case study, developed within the scope of the Collaborative Research Center Transregio 29 with the topic of "Industrial Product-Service Systems". The case study is described in detail in [23] and [24].
The above-mentioned case study simulates the business-to-business relationship between two industrial companies and considers different business models. The offered IPS2 consists of a micro milling cell integrated with value-added services, e.g. the optimization of the customer-specific production process. The approach proposed in the current article has been validated based on the availability-oriented business model. In this business model, an IPS2 is delivered to the customer with the guarantee of high performance and is usually integrated as a production unit into a customer production process. Because of dynamic changes and uncertainties in the IPS2 use phase, IPS2 suppliers have to control and improve their IPS2 during its use phase.
Web-based interface (outgoing/ incoming)
I Industrial Product-Service Module
Service Product
Fig. 3. SOA-based environment for information exchange
The most important advantages of an SOA-based approach for building up an IPS2 network are the facts that IT-architecture comprise a high compatibility with existing structures (R1.1), high reusability of services (R2.1) and flexibility in adapting to changing business requirements
^Development Phase Operation Phase
IPS2-Lifecycle Management System 4
IPS2-Execution System
IPS2-Control Systems
Fig. 4. Conceptual scenario for the interplay within IPS2 networks
Figure 4 shows the conceptual scenario for the interplay within IPS2 networks, especially the interaction between the IPS2-LMS, the IPS2-ES and the IPS2-CS. After the development of an IPS2, the information about goods and their components are sent to the IPS2-CS. At the same time, data about the IPS2 service model and the partner network are transmitted from the IPS2-LMS to the IPS2-ES (1). The model includes information about delivery process requirements, for example necessary competences of the workers and type of
needed tools or spare parts. This data is used by the IPS2-ES to create the delivery plan by mapping available resources provided by the partners in the IPS2 networks to delivery processes. The delivery plan is then forwarded to the IPS2-CS, which monitors the IPS2 (2). Whenever the IPS2-CS observes that an unplanned demand arises, it requests the scheduling of a new delivery process for the IPS2 from the IPS2-ES (2).
The IPS2-ES in turn updates the delivery plan and forwards this information back to the IPS2-CS. Parallel to this communication scheme, the delivery plan is always forwarded to the IPS2-LMS (3). This information will be connected to other data of the related IPS2, for example information about required steps in a process's execution or machine history (4). Prior to and during the execution of the delivery process, the service technician can interact with the IPS2-LMS to receive the required information he is entitled to (5). After the execution, feedback from the service technician is reported to the IPS2-LMS. The sequence of the communication for steps (1) to (3) is depicted in Fig. 5.
IPS2-CSfor IPSZ 1..n
IPS2 Service Shares and
Partner Network
Delivery Plan
Delivery Plan
IPS2 Product Shares (BoM)^
Message — Execution —
for IPS2 n Strategic Capacity Planning Delivery Plan (for IPS2 n) _
Schedule New Delivery
Process for IPS2 n
Operational Resource ^^ Planning
Delivery Plan (for IPS2 n)
•-"-tps2 Control of IPS2 n
Fig. 5. Sequence diagram for the interaction of IPS2-LMS, IPS2-ES and IPS2-CS
The following example demonstrates the developed concept with the focus on the IPS2-LMS and the IPS2-ES. An IPS2 is developed for the customer Omichron who ensures technical as well as organizational availability of a micro milling machine. An IPS2 model is developed which contains the delivery processes of maintenance, repair and delivery of cutting tools. The maintenance process is needed to ensure technical availability, the delivery of cutting tools is required for organizational availability and the repair process enables the IPS2 provider to restore the availability as a reaction to an unexpected defect.
The processes including their periodicity and their requirements, e.g. technician qualification, needed tools or spare part types, are pushed to the IPS2-ES using a Representational State Transfer (ReST, [25])-based web service called "StoreDeliveryProcesses". Information about newly added or removed partners in the provider network will be pushed through the ReST-based web service
"AddNetworkPartner" or "RemoveNetworkPartner" respectively. This leads to communication step (1).
The IPS2-ES starts the strategic capacity planning and generates the delivery plan. The plan includes the scheduled maintenance and delivery processes of cutting tools complying with their periodicity. For each process, the plan determines which resources are involved in the delivery. When a new plan is available, the IPS2-ES informs all involved network partners and the IPS2-LMS is triggered via its Simple Object Access Protocol (SOAP, [26])-based web service "NewPlan" so that it can retrieve the generated plan via the IPS2-ES ReST-based web service "GetNewPlan" (3).
The IPS2-LMS connects the needed information for each of the planned delivery processes. This will include a process description, historical delivery data on the generic delivery process and the related product share (4) for each maintenance process. Each human resource involved in the delivery processes can access the IPS2-LMS via a web-based cloud service using a specific delivery process ID to retrieve above-mentioned information (5). Furthermore, the resource can post its feedback directly via the cloud service so it can be used to optimize the delivery process (see Fig. 6).
Login as: Employee t | Logout Search
LiCS ^1
Product Service Systems - Litccyclc Cloud Service Solution
Llfecycle phases
Planning Development Implementation
BoM Structure
a - SW123
Components related Information
Manufacturer: Omni Consumer J 'I'l l: üRnje: OtM Installation: Mirroring
« Payload
Repair reports
« Repair: Delivery Process
ft Firmware
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Fig. 6. Screenshot of information retrieval via a cloud service
This exchange of information is consistent while the availability of the IPS2 is still guaranteed. However, when the IPS2-CS detects a damaged component or a shortage of cutting tools, it informs the IPS2-ES that it needs to schedule a new delivery process, either a repair process or an additional delivery of cutting tools (2). After running an operational resource planning algorithm, the newly created delivery plan is again transmitted to the network partners and the IPS2-LMS (3), which again adds information (4) for retrieval by service technicians (5).
4. Conclusions and Outlook
The current paper provides an overview of different management perspectives of IPS2 and presents an SOA-based architecture for the interplay and integration of different domain-specific systems within the IPS2 network. In order to
implement the SOA-based architecture, different web service-based interfaces are developed and validated in a scenario. This approach makes it possible to manage dynamic networks and deal with changing partners. Furthermore, it facilitates the integration of several heterogeneous and independent software systems, not only newly developed IPS2 systems but also existing systems of different domains. Hence, the integration of different management perspectives is accomplished.
To be able to use our approach, an IPS2 provider has to have implemented the IPS2 Lifecycle Management and IPS2 Delivery Management as a foundation. This means that amongst his duties are the management of the whole IPS2 lifecycle related information and the management of the IPS2 dynamic network.
The implemented approach is using direct communication between the different software systems. While this approach is suitable for a prototypical implementation, this approach also implicates restrictions with respect to the extensibility and easy substitution of systems. For example, the different technologies ReST and SOAP used for web service communication have to be supported by all involved IT systems, depending on which interfaces have to be used. For future work, an enterprise service bus environment using, for example, the Oracle Fusion Middleware can be established to improve the above-mentioned SOA architecture. Such middleware enables the reuse of existing services and development of new services for the change of business processes during the IPS2 lifecycle using Business Process Execution Language (BPEL). It also allows for a mapping between technologies like ReST and SOAP. By using this approach, the integration of new IT systems becomes less tedious.
Acknowledgements
We express our sincere thanks to the German Research Foundation (DFG) for financing this research within the Collaborative Research Project SFB/TR29 on Industrial Product-Service Systems - dynamic interdependency of products and services in the production area.
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