A Conceptual Model for Product Service System ( PSS ) 2

Servitization or productization, indicating evolution from product to service economy or 16 vice-versa, can be considered as a successful strategy to gain competitiveness based on novel 17 combination of products and services. To decrease the risks of servitization and to support the 18 sustainable development of its main outcome, being Product Service System (PSS), it is required not 19 only to have a clear and common understanding of the core business and processes but also to share 20 the same definitions on (PSS) concepts as the main outcome of servitization. For this purpose, 21 managers could be supported by abstract models with a limited number and high ratio of known 22 concepts in the early stages of PSS development. Through an extensive literature review on this 23 subject, followed by a structured conceptualization approach and discussions with domain experts, 24 this paper proposes a Conceptual Model (PSS-CM). To validate the results, PSS-CM and its elements 25 were discussed in several iterations, from both academic and industrial points of view, in the frame 26 of a European research project. In the frame of this project, a case study was also performed to 27 illustrate the instantiation of PSS-CM. 28

). It should be mentioned that, this extended analysis 125 highlighted the lack of approaches with strategical purpose supporting enterprise managers who 126 plan and control the servitization and PSS development process.

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3. The information subsystem includes information from the physical sub-system and from the In this step, PSS was analyzed as a dichotomy of product-related and service related concepts.

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Among the definitions proposed in the state of the art, the ones proposed in the context of 156

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The PSS definition proposed in MSEE project is: "a collection of interrelated components that are 227 organized for a product service related purpose, i.e. to design, to produce, to manage and to deliver product

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Considering the above definitions, the following points can be highlighted (see Table 2

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It also requires an infrastructure supporting product usage and service delivery.  were studied. These classifications are summarized in Table 3. While initial approaches were or parts of it were replaced by services, e.g. cloud services that replace hardware storage capacity.
differentiation in comparison with competitors.

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Definitions are proposed in the following paragraphs for the key elements (i.e. classes and 336 attributes) of PSS-CM. Other elements such as associations and cardinalities are described in Table   337 A1 of Appendix A. To perform a preliminary validation, the elements and definitions were discussed    Table 4).  The objective behind the formation of the ecosystem.

Policy
The set of rules for regulating collaborations among stakeholders in the ecosystem.

maturity
History of the collaboration between stakeholders within the ecosystem.

cost/Revenue
Overall cost and revenues of the stakeholders plus the cost for forming and maintaining the ecosystem. Stakeholder

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Stakeholders manage or perform processes which are supported by resources. To complete the 368 definition of stakeholder, the following key attributes can be mentioned (see Table 5).

objective(s)
Expectation and desired evolution for the global performance of the stakeholder. The objectives, at this level, results from the aggregation of process-specific goals.

etc.
Other attributes according to the specific needs (e.g. Strategy, Legal form, Finance, etc.).
Product [class]: It represents a tangible component of the P-S bundle. It is a tangible physical 371 entity or a good which is sold to customers responding to their needs. The definition of this class can 372 be completed with the following key attributes (see Table 6).

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A Service is performed: by a system which has a "substantial knowledge", for a customer, in co-

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creation with him and eventually other stakeholders, with intangible results and economic added 377 value, with results that could be delivered remotely. Service should be delivered continuously; 378 otherwise, it disappears after being delivered. The following key attributes are considered for service 379 (see Table 7).

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consists of a mix of tangible products and intangible services with a specific association. The

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following key attributes can be considered for this class (see Table 8). The links between the P and S related activities all along P-S life-cycles (e.g. resource allocation). It can be: (1) independent, (2) correlated, (3) collaborative or (4) symbiotic.

typeBusinessModel
The business relation between the product and service (e.g. type of value proposition, channels, resources, etc.). It can be: (1) separated, (2) bundled, (3) joint or (4) Symbiotic. costPriceValue A product-service has a cost and a price (not always the sum of product and service costs).

Topology
The configuration of cyber and physical part of a P-S. It can be: (1) Separated Cyber-Physical, (2) Distributed Cyber-Physical, (3) Edge Cyber-Physical or (4) Symbiotic Cyber-Physical.

Interoperation
The level of exchanges between the product and service systems in terms of data, knowledge and processes. It can be: (1) Isolated, (2) Data Exchange, (3) Knowledge Sharing or (4) Symbiotic. status The development stage of a P-S. It can be: (1) Idea, (2) Concept, (3) Prototype or (4) Industrialized.

SustainabilityGain
The reduction in environmental impacts thanks to the novel combination of products and services.
Process [class]: It is a structured set of activities into which an enterprise system can be 387 decomposed. Examples of process can be design, planning, production, quality check; delivery, etc.

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The definition of process can be completed with the following attributes (see Table 9). shared between the processes. To complete the definition of an activity, the following key attributes

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• PhysicalEntity [class]: It represents physical means involved in the P-S development.  costPriceValue several concepts about production cost, salary, price or the value of the component in PSS.

Human [ComponentResource] type
(1) person or (2) team, i.e. a single employee or a group of workers acting as a whole.

Profile
Details of the person, such as his/her role, responsibilities, activities, seniority and experiences.

skillAndCompetence
The capabilities of the human resource.

PhysicalEntity [ComponentResource] type
The category of the component: (1) Table 12). The interval after that the PI is (re)measured to find potential deviation from the target value.

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measuredValue PI value resulting from the monitoring system.

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To complete the generated model (the XMI file), first two main classes were created as parts of 465 the Ecosystem which is the root (see Figure B1 in

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Other classes were then created as parts of the Stakeholder and ProductService classes (see Figure   473 B2 in Appendix B).

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Following the above tasks in a hierarchical way, all the classes were added to the model until 475 reaching at least one instance (example) of each concept. An excerpt of the model is illustrated in Figure B3 (see Appendix B). Then, for each class instance, the properties (i.e. attributes and 477 associations) were quantified.

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An example is illustrated in the Figure B4

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To define / understand a PSS using PSS-CM, a top down approach can be followed. It is mainly 504 critical to first reach a common understanding on the new concepts (e.g. product-service and its 505 attributes) and their association with more known concepts (e.g. activity, resource etc.). In other 506 words, the results of PSS conceptualization approach are followed in reverse from the upper layer 507 (PSS-specific concepts) to the core (system concepts) of the model.
Decision framesDecision 0..* A decision can (or not) limit the decisional frame of other ones. affectsProcess 1..* A decision, to be relevant, must influence at least one process in the company. Some decisions, mainly at strategical level, have impact on several processes. isMadeByHuman 1..* A decision involves one or many decision-makers. Simple decision, in everyday running at operational level, can be taken from single persona while strategical decisions usually involve several people with different skills, competences and roles. isSupportedByICT 0..* A decision may (or not) be supported by one or several tools.