Merouane Youssef Bouanan
email: youssef.bouanan@ims-bordeaux.fr

El Alaoui

Grégory Zacharewicz

Bruno Vallespir
email: bruno.vallespir@ims-bordeaux.fr

Merouane Bouhamidi

Gregory Zacharewicz
email: gregory.zacharewicz@ims-bordeaux.fr

Using DEVS and CELL-DEVS for Modelling of Information Impact on Individuals in Social Network

Keywords: DEVS Formalism, Information Impact, CELL-DEVS, Human Behaviour Modelling

de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction and Motivation

The reactions of populations to the dissemination and propagation of information are, up to now, not modeled appropriately. There is however an interest in the ability to simulate and accurately measure the impact of information on population. The SICOMORES project objective is to provide solutions to artificially generate structured social networks of realistic population and simulate the effects of information on population, with a propagation algorithm of the effects across networks. The intention is to go further than current models which generally reduce the individuals of a population as simple obstacles or information transmitters without enough nuances in their behaviour and the influence they can have on a message. This paper intends to present the premise of modelling and simulation of the impact of influence activities on individuals in social networks using Cell DEVS M&S formalism.

Cell-DEVS is a combination of CA (Cellular Automata) with the DEVS (Discrete EVent system Specifications) formalism that allows the definition of complex cell based systems. It appears especially suited to this study that takes into account several layers of social graph related with geographical networks. CD++ is a modelling and simulation tool that implements DEVS and Cell-DEVS. We use CD++ to build a model of influence of information on individuals in social networks. In more detail, this paper will participate in the definition of a set of models that addresses the entities and the structure of a population. It will present a state of the art of modelling and simulation approaches to describe a social system at multiple levels including multiagent systems (MAS) and discrete modelling approaches. In addition, it will provide models of individuals and groups of individuals characterized by a set of state variables (e.g. Using Maslow to construct the behaviour of an individual) and the mesh between the individuals within a social network.

Background

DEVS Formalism

The DEVS formalism for modelling and simulation [START_REF] Zeigler | Theory of Modelling and Simulation[END_REF] is based on discrete events, and provides a framework with mathematical concepts based on the sets theory and systems theory concepts to describe the structure and the behaviour of a system. With DEVS, there is an explicit separation between a model and its simulator: once a model is defined, it is used to build a simulator (i.e. a device able to execute the model's instructions). DEVS knows two kinds of models: the atomic models, which describe behaviour, and the coupled models which describe a hierarchy. The tiniest element in DEVS formalism is the atomic model. It is specified as: AM = < X, Y, S, ta, δint, δext, λ >

The semantics for this definition is given as follows. At any time, a DEVS atomic model is in a state s Î S. In the absence of external events, the model will stay in this state for the duration specified by ta(s). When the elapsed time e= ta (s), the state duration expires and the atomic model will sent the output λ(s) and performs an internal transition to a new state specified by δint (s). Transitions that occur due to the expiration of ta(s) are called internal transitions. However, state transition can also happen due to arrival of an external event which will place the model into a new state specified by δext (s,e,x); where s is the current state, e is the elapsed time, and X is the input value. The time advance function ta(s) can take any real value from 0 to ¥. A state with ta(s) value of zero is called transient state, and on the other hand, if ta(s) is equal to ¥ the state is said to be passive, in which the system will remain in this state until receiving an external event.

Table 1 show the graphical notation to define the behaviour of atomic models.

CELL-DEVS

Cell-DEVS [START_REF] Wainer | Discrete-Event Modeling and Simulation: a Practitioner's approach[END_REF] has extended the DEVS formalism, allowing the implementation of cellular models with timing delays. It improves execution performance of cellular models by using a discrete-event approach. It also enhances the cell's timing definition by making it more expressive. Each cell is defined as an atomic model using timing delays, and it can be later integrated to a coupled model representing a cell space, as showed in Figure 1.

Fig. 1. Informal Description of Cell-DEVS

Once the cell behaviour is defined, a coupled Cell-DEVS can be created by putting together a number of cells interconnected with their neighbors. A cellular model is a lattice of cells holding state variables and a computing apparatus, which is in charge of updating the cell state according to a local rule. This is done using the present cell state and those of a finite set of nearby cells (called its neighborhood).

Each cell uses N inputs to compute its next state. These inputs, which are received through the model's interface, activate a local computing function (t). A delay (d) can be associated with each cell. The state (s) changes can be transmitted to other models, but only after the consumption of this delay. Two kinds of delays can be defined: transport delays model a variable commuting time (every state change is transmitted), and inertial delays, which have preemptive semantics (scheduled events can be discarded).

CD++ Toolkit

CD++ [START_REF] Wainer | CD++: a toolkit to develop DEVS models[END_REF]) is a modelling and simulation toolkit that implements DEVS and Cell-DEVS theory. Atomic models can be defined using a state-based approach (coded in C++ or an interpreted graphical notation), while coupled and Cell-DEVS models are defined using a built-in specification language. We will show the basic features of the tool through an example of application. CD++ also includes an interpreter for Cell-DEVS models. The model specification includes the definition of the size and dimension of the cell space, the shape of the neighborhood and borders. The cell's local computing function is defined using a set of rules with the form: {POSTCONDITION} {DELAY} {PRECONDITION}. These indicate that when the PRECONDITION is satisfied, the state of the cell will change to the designated POSTCONDITION, whose computed value will be transmitted to other components after consuming the DELAY.

Human Behaviour Modelling

General approach

Human Behaviour Modelling is an important area of computational science with implications not only for social sciences, but also for economics, epidemiology and other fields. Scientific literature abounds in heterogeneous and highly specialized, theoretically founded concepts of human cognition, emotion and other behaviour aspects.

There are many lines of research on such models, which span several disciplines, have different goals, and often use different terminologies and various approaches. Human behaviour modelling or human behaviour representation (HBR) is an important field of study in military service research [START_REF] Fei | Verification of Human Decision Models in Military Simulations[END_REF], robotics [(Kubota and Nichida, 2006)], brain-computer interface (BCI), human machine interface (HMI) and some specially oriented anthropology studies. Human behaviour models are often represented by finite state machines, rules, fuzzy rules [START_REF] Dorsey | Mathematical Modeling of Decision making: A Soft and Fuzzy Approach to Capturing Hard Decisions[END_REF], artificial neural networks, multi-agent based modelling [START_REF] Sun | Multi-Agent Based Modeling: Methods and Techniques for Investigating Human Behaviors[END_REF]. The need for a variety of modelling paradigms stems from the fact that the different domains of knowledge needed to represent human behaviour cannot be done by only one paradigm.

Using DEVS for Human Behaviour Modelling

Human behaviour can be difficult to understand and predict, thus it can be qualified as a complex system. DEVS is a well-defined formalism which has numerous advantages over other formalisms in the modelling of complex dynamic systems. A few related works have provided DEVS models of human behaviour that we will use with slight modifications; [START_REF] Seck | Using DEVS for Modeling and Simulation of Human Behaviour[END_REF]) present a DEVS based framework for the modelling and simulation of human behaviour the influence of stress and fatigue, (Fau-cher, 2012) proposed a first approach using G-DEVS formalism for Civil-Military Cooperation actions (CIMIC) and Psychological actions (PSYOPS), which are actions of influence that take precedence over combat. The purpose of this work is to go beyond previous works by providing a simple model but more performant and accurate which will allow us not only to model the behaviour of an individual, but also the simulation of the propagation of an information among a group of individuals and its influence on their behaviour.

This model (Figure 2) is describing the influence of message on the behaviour of an individual and potentially its dissemination. The first state consists in being in contact with another agent in its social network neighbourhood and calculating the strength of connexion between them. When the message is received, it creates an impact on the individual which change its behaviour eventually depending on the strength of the message [START_REF] Faucher | PSYOPS and CIMIC operations: from concepts to G-DEVS models[END_REF]. Then, if the message strength is still strong enough the receiver is preparing on its turn to transmit the message to its network neighbours considered as target info. The phenomena of information propagation have known a great interest of researchers and still an active field of research as well [START_REF] Bakshy | Everyone's an influencer: quantifying influence on twitter[END_REF]. In the past, the propagation was mainly studied in the epidemiological field to better understand the process of propagation of infection in certain conditions. Therefore, the majority of recent works related to information diffusion are based on the epidemic researches.

There is a basic analogy (Table 2) between the dissemination of information among a group of individuals and the transmission of infectious disease between the individuals themselves. In the two cases, something is communicated through a given contact.

Epidemiology

CELL-DEVS implementation

The following figure shows the procedure steps of model executions in CD++. We used and adapted according to the transposition proposed in the Table 2 an existing model of virus spreading defined with CELL-DEVS [START_REF] Shang | A Model of Virus Spreading Using Cell-DEVS[END_REF], (CELL-DEVS, 2014).

Fig. 3. Execution result at time 00:00:00:000; 00:00:00:500; 00:00:01:000

The model is intended to study the propagation of information within a group of individuals. Assume there is 20×20 mesh of cellular automata (CA). Each individual, residing in (i,j) node, is equipped with a number ranged from 0 to 9 indicating different Parameters of the individual. Each cell may represent one of two categories: one is person who did not receive the information represented by white color; the other is the person who received the message represented by red color. The individual can be opposed to the information and/or person that is transmitting the message and/or favourable to the emitter and message content. The simulation results show on the right picture of Figure 3 that depending on the opinion of individuals and the configuration of the social networks some individual can be reached by the information where some other not. This test is very simple; it is based on the abstract geographical situation of individuals and it takes into account only one dimension of a social network. We have not introduced yet the graph representation for defining the multilevel social network links between individuals or groups. Nevertheless the approach already validates the possibility to reuse epidemic algorithm for information spreading.

Conclusion

This paper introduced Formal Modelling and Simulation of the impact of Information on Individuals in Social Networks. We have presented how DEVS and Cell-DEVS can be very useful techniques for modelling and simulating of Social influence. At the individual level, the DEVS model proposed is very simple keeping raw Maslow parameters as state variables and being simply influenced by arriving messages. In its turn the individual model can transmit the message after having potentially transformed its strength according to several criteria. The Cell DEVS structure then use these models of human extremely simplified and start building on top of its connected modules to form Cell-DEVS network. In addition, the separation between the model simulator followed by DEVS and CD++, has enabled the modeller to concentrate on building the behavioural model on one side and preparing the spreading logic on the other side using the CD++ toolkit. The model shows a correct, even very simple, human behaviour impact regarding information perception and treatment. Then the information spreading reusing the epidemic approaches seems accurate after some adaptations to propagate the information over the network.

Perspectives

The main perspective remains the definition of a multi-level social network. In detail the real social network is complex, it can refer for e.g. to the family environment, work, religion, geography to transport the information from one individual to another. The final result will be the combination of several networks graphs. The next step will also consider other experimental terrains, for instance enterprise and organization.

Fig. 2 .

 2 Fig. 2. DEVS individual model

Table 1 .

 1 DEVS graphical notation

Table 2 .

 2 Analytical model parameters in epidemiology versus diffusion

	Information diffusion


Ihssan M Jwijati

Umit S Bititci

Keywords: performance measurement, cross-cultural management, change management, SME

The purpose of the research presented in this paper is to explore the impact of national culture on the design, implementation and use of performance measurement systems (PMS). Managing performance of organizations using management control system or performance management systems is essential for managers. As organizations are increasingly having to expand globally, they are forced to operate their original PMSs, but in different cultures. While, the impact of culture on PMS implementation have been revisited in the performance management literature from organizational perspectives, the impact of national culture on PMS was not clearly explored. Therefore the aim of the authors is to explore the impact of national culture on the lifecycle of PMS. Qualitative inductive research approach, and semi structured interviews of indigenous SMEs' were employed, and the findings suggest that national culture impact PMSs lifecycle and propositions are provided explaining the expected behaviour of different national cultures.

Introduction

Traditionally, measuring performance in organizations used to be achieved by monitoring financial performance only, until a time when the inadequacy of this approach was questioned by scholars such as [START_REF] Johnson | Relevenece Lost: The Rise and Fall of Management Accounting[END_REF]. The use of 'balanced' performance measures was advocated by many scholars such as [START_REF] Kaplan | The balanced scorecard -measures that drive performance[END_REF], Neely (1996), and others. However, PMS implementation had high failure rate according to [START_REF] Neely | Why measurement initiatives fail[END_REF], which lead the scholars to discover different forces behind successful implementation. Among the important factors that impact PMS design, implementation and use is culture. Culture according to [START_REF] Bourne | Designing, implementing and updating perormance measurement systems[END_REF], is one of the important drivers of successful PMS implementation. However, most of these studies have been conducted from an organisational culture view point according to [START_REF] Henri | Organizational culture and performance measurement system[END_REF], and because of our vague understanding of the impact of national culture, [START_REF] Otley | Management control and performance management: whence and whither?[END_REF] has called for more research to be performed to understand the impact of national culture. In addition, as we move deeper in to the 21st century we are seeing new forms of work emerging,

Exploring the Impact of National Culture on Performance Measurement

particularly with globalisation, advances in ICT technologies as can be experienced with global multinationals operating in different cultural settings as well as networks of smaller organisations collaborating in global networks (Bititci et.al., 2011). Furthermore, with the increasing impact of the emergent markets, organizations' need to conduct and manage businesses in other countries is more than ever, hence each organization should be able to cope with its internal and external environment in any country, as internal contextual factors are impacted with individuals' behaviour and culture.

Therefore, exploring the impact of national culture on PMS will help us contribute to the existing literature on performance measurement by (i) exploring the impact of national culture on the lifecycle of performance measurement systems, (ii) investigating moderating factors which is affecting the impact of national culture in organizations, and (iii) proposing methods of how to guide PMS implementation in different cultures.

Background Literature

National Culture

National culture (NC) has been defined by Hofstede as 'the collective programming of the mind which distinguishes the members of one human group from another' (Hofstede & Hofstede, 2005). The definition implies that culture is particular to one group and not others, and culture includes system of values. [START_REF] Schein | Organizational Culture and Leadership[END_REF] has suggested that culture is the way in which a group of people solves problems and reconciles dilemmas. [START_REF] Kluckhohn | Variations in value orientations[END_REF] Trompenaars and Hampden-Turner (1993) created their framework on relationships of subordinates and rules (universalism vs. particularism), their relationship to the group (collectivism vs. individualism), their feelings and relationships (neutral and affective), the extent of their involvement with their tasks (specific vs diffuse), how status is awarded (ascription vs. achievement), how time is managed (synchronic vs. sequential) and how people relate to nature (Internalist vs. externalist).

Performance Management Systems

Traditionally, measuring performance in organizations used to be achieved by monitoring financial performance only, until a time when the inadequacy of this approach was questioned [START_REF] Johnson | Relevenece Lost: The Rise and Fall of Management Accounting[END_REF]. They advocated the use of non-financial measures in addition to financial measures in their seminal book the relevance lost. This lead many scholars to the introduction of different approaches such as [START_REF] Kaplan | The balanced scorecard -measures that drive performance[END_REF] Balanced Scorecard (BSC), Neely's performance prism, (Neely et al., 1996) among other performance frameworks. As the proliferation of PMS grew, as well as the failure rate of PMS implementation which amounts to 70% according to [START_REF] Neely | Why measurement initiatives fail[END_REF]. Attention then shifted from investigating implementation enablers and barriers to how to better use PMS results (Bourne et al, 2004).

Successful implementation of PMS depends on many factors such as: management commitment (de Waal, 200;[START_REF] Assiri | How to profit from the balanced scorecard: An implementation roadmap[END_REF][START_REF] Henri | Organizational culture and performance measurement system[END_REF], aligning of strategy, [START_REF] Kaplan | The balanced scorecard -measures that drive performance[END_REF][START_REF] Bourne | The success and failure of performance measurement initiatives: Perceptions of participating managers[END_REF][START_REF] Assiri | How to profit from the balanced scorecard: An implementation roadmap[END_REF], and culture [START_REF] Bourne | Designing, implementing and updating perormance measurement systems[END_REF][START_REF] Bititci | Dynamics of performance measurement and organisational culture[END_REF], among other factors. Culture is one of the important drivers or factors impacting implementation of PMS [START_REF] Henri | Organizational culture and performance measurement system[END_REF][START_REF] Bititci | Dynamics of performance measurement and organisational culture[END_REF][START_REF] Bourne | Researching performance measurement system implementation: the dynamics of success and failure[END_REF]. Although national culture's impact has been researched in management control literature with mixed results, yet it's impact has not been properly investigated by performance management researchers. Otely ( 2003) has called for more research to understand the impact of national culture in performance management systems. It is therefore, vital to understand, the impact of national culture on PMS, as we are moving deeper in to the 21st century with new forms of work emerging, particularly with globalisation, advances in ICT technologies, network of smaller organisations collaborating in global networks [START_REF] Bititci | Performance Measurement: Challenges for Tomorrow[END_REF]. [START_REF] Henri | Organizational culture and performance measurement system[END_REF] has found out that PMS can be used in four ways: monitoring, attention focusing, strategic decision-making, and legitimization. Monitoring when PMS provide feedback regarding performance to various stakeholders. If the results are used as a facilitator, then it is strategic use, while using the results to justify decisions or actions it legitimization. When the results are used to send signals throughout the firm, then the use is attention focusing or communications.

Methodology

In order to explore the impact of national culture on performance management systems, inductive qualitative research method was employed, as its more suitable for answering 'why', and 'how' questions in an iterative and flexible way, where the researcher's positions forms an integral part of the research process [START_REF] Voss | Case research in operations management[END_REF] and Barratt et al., 2011). The research method used is multi-case study approach because it allows the researcher to explore the way companies in different cultures design, implement, and use their performance systems. The criteria for choosing different national cultures is based on Hofstede's Power Distance v Uncertainty Avoidance matrix as Hofstede suggested that there is an empirical evidence regarding the relationship between the country's position within the PD-UAI matrix and organizations' behaviour. Four cultures were chosen one from each quadrant in the PD-UAI matrix (Hofstede & Hofstede, 2005). The empirical study involved two Chinese, two Italian, two Syrian and two UK manufacturing SMEs. For each company we collected information about PMS, PMS processes. Indigenous SMEs were chosen, as we expected large companies' policies, practices, and other factors to impact the influence the culture of the organisation. Additionally, in order to ensure that the chosen organizations representing their national cultures, only indigenous companies were chosen. All the case studies were having similar organization size, all were privately owned, all have industrial background, with minor differences in the firms' years of operation. Finally, ensuring -as much as possible-the clear impact of national, all case study organizations were chosen from non-regulated manufacturing sectors.

Wherever possible, interviews were held with the general managers and their top management teams. In one of the Chinese interviews, the decision maker was accompanied by members of his middle managers, where they participated in the discussion. In one of the Syrian organizations, the decision maker was interviewed alone in the beginning, and later the researcher was given time with two of the middle managers. It should be mentioned that the setting was left to the organizations involved, with the researcher expressing his wish to increase the scope, the length of the interview when the research needed more depth. In order to ensure objectivity, the interview result was triangulated with information company documents as well as researcher observations. In preparation for the company visits, a research protocol was designed. The research protocol was discussed between the authors and elaborated upon, and any question regarding the content was answered. Initially, the research protocol was piloted and tested on one UK organization, then the results of the interview was discussed, and minor changes were acted upon the research protocol, and then employed on the other case studies.

Semi structure interviews, observations, and archival sources were used to collect data, justified by the inductive nature of the research. The semistructured nature of the interviews added exploratory richness to the research findings. Notes collected from interviews were prepared in a report that included observations from researcher, and relevant data from different sources such as internet sites or media reports. Visits to the company site helped in clarifying the nature of the organizations. Interviews were conducted by one researcher in three cultures, and conducted by another collaborating researcher for the fourth culture. Indigenous languages were the languages employed for each culture reducing translation errors. The number of researchers was ranging from one to two in the four cultures with interviewers discussing their notes on the interview. The length of the interviews depended on achieving the aim of the research ranging from two to three hours. Eight organizations were visited in the process of research. Each company is denoted by the name of culture, then C. No. denoting to the case number.

Findings

It seems that there is a pattern emerging across these eight cases with respect to the impact of national culture on PMS design and use. These patterns may be summarised as follows.

3.1

Chinese Culture In Chinese companies with family organization culture, PMSs are designed by the top management board, with little input from the middle managers. The PMSs is formal, with formal meetings discussing the results. The use of PMS has been observed is mainly in managing strategy, in monitoring, communication, influencing behaviour, but not used in learning and development. The reason could be attributed to family culture, where this could be attributed to employees' obedience, stemming from the Chinese cultural value of vertical social order. Employee's willingness to cooperate and make the measurement process workable, and this could be to the Chinese cultural value of individual 'face' and reputation. The results resemble the results found by [START_REF] Li | Performance measurement design within its organisational context-Evidence from China[END_REF].

3.2

Italian Culture In the Italian culture, we can see two organizations with two different organization cultures. The first organization with an incubator culture, has deliberately designed its PMS by middle management, with balanced measures where we witnessed a highly used system in managing strategy, monitoring, communication, and learning and behaviour. In the second organisation with a family culture the PMS was designed by the top management with emphasis on financial measures. We observed evidence of resistance in its implementation where the PMS is mainly used for monitoring and legitimization.

3.3

Syrian Culture In Syria, PMS used were mainly financial, but it was observed that the comprehensive use of PMS is reserved for the top manager. Middle managers used the measurement in their daily activities, but cross cooperation between managers was limited. The reports are kept with the top management, who in turn keep it under lock and key. Here PMS is used in legitimisation, which make some middle managers resistant to the measurement process, but it could said that the top managers are the main benefactor of the measurement who keep the result hidden from their managers, in a knowledge is power and divide and conquer approach.

3.4

UK Culture In the UK, we have two organizations with two different decentralized cultures. The first UK organization is and incubator with an emphasis on people. It has a well-developed set of measures which is used for all purposes except legitimisation. Its use for learning and improvement is highly emphasised. The Second UK organisation is a guided missile with a greater task emphasis. It has less developed measures that are informally used for monitoring, communication, influencing behaviour purposes. Its use for learning and improvement is limited.

Impact of high power distance on PMS

It seems that high PD culture is associated with command and control use of PMS. Here the PMS systems are designed by top management only, where the role of middle management is diminished. As seen in Syria cases 1 & 2, China cases 1 &2, and Italy C.2. The high influence of top management is probably attributed to the high power distance, which leads to little or no middle management participation. The little involvement has probably lead to the reaction of middle management by mostly being either indifferent, or resentful or non-compliant to the measurement process. The difference between China and other high PD cultures could be due to Guanxi, which means in the Chinese culture "relationships" or "connections". Good guanxi will ensure minimization of conflicts and frustrations. It aims at building a supportive, genuine relationship founded on reciprocal respect [START_REF] Yin | An analysis of factors of success for Chinese/ European JVs in culture aspect[END_REF]. The only case that had some participation from the middle managers among the low PD was Syria C.1 case, and this may be attributed to the focus of the company's strategy on gaining market share, and educational level of these managers, or the high education level of the middle managers.

Impact of engaging strategy on PMS use

It seems that organizations that shift decision making to middle management have better developed and used PMS. For example, in UK C.2, the performance measures are designed by middle manager, where the use of measures is through daily meeting, and where performance results are shared, elaborated in decisions making. Engagement has resulted in ownership of PMS design, implementation and use. However, is the high degree of use related to the flexible nature of the organizational culture? More research should address the impact of flexible organizational culture on the design, implementation and use of PMS.

Discussion and Conclusions

In high PD cultures one of the purposes of PMS is legitimisation, while in low PD cultures legitimisation is not a purpose for PMS. Low uncertainty avoidance cultures are associated with more democratic use of PMS Although national culture seems to have some influence on the design and use of PMS in organisations, some strategic characteristics of the organisation also influence the design and use of the PMS…e.g.  Strategy, it has been seen where innovation is a competitive requirement we are observing a more decentralised behaviour within the organisation that is accompanies with more empowered/delegated design and democratic use E.g. Italy C.1  Governance structure of the organisation and possibly its history can affect the design and use of the PMS… e.g. China C.1  Personality and outlook of the leadership has an impact on the use of PMS. For example in Italy. In C.1 the organization is lead by a relatively young management, with an innovation focus leadership, while in C. 2, where the leadership is conservative, the PMS aims go to monitoring only, not as far as Italy C.1 with innovation at the core of PMS. In Syria, such a difference exists between C.1 and C.2.

Concerning the design of PMS… uncertainty avoidance can impact the way performance information is communicated/shared in the organisation. For example, in high uncertainty avoidance cultures, information is circulated with caution in 'need to know basis' as seen in the Syrian organizations. Empowered approach is more helpful to gain the support and engagement from the employees. While in Chinese cases it was seen that PMS in high power distance cultures are of low maturity systems, command and control system. The more engagement will have more democratic systems. Although in the high PD and UCI cultures like Syria the closed secretive behaviours displayed by the top managers lead to themselves designing and using the PMS which in turn leads to significant resistance from other managers… A more empowered approach to the design and implementation of PMS although counter intuitive to top management behaviour may yield more sustainable results with more ownership and resistance from the organisation

Acknowledgements

The authors would like to thank Dr Patrizia Garengo from the University of Padova, Italy, and Dr Dan Wang from Harbin University for their invaluable assistance in collecting, translating and involvement in the data.


Siham Lakri
email: siham.lakri@ecp.fr

Yves Dallery
email: yves.dallery@ecp.fr

Measurement and Management of Supply Chain Performance: a Benchmarking Study

Keywords: Supply chain, Performance measurements, Performance management, Benchmarking study

Over the past few decades, the role of Supply Chain (SC) has been evolving from cost centre to competitive advantage. That is why measurement and management of SC performance become particularly essential. However, such an undertaking is difficult due to the growing complexity of SC. As the literature review highlights it, there is a lack of survey dealing with measurement and management of SC performance, collecting data through interview process and especially addressed to large companies. This is the bias of the present paper. First, an overview of the benchmarking published on related topics is presented. Then, are detailed the selected sample, the methodology used to collect and analyse data and the preliminary results obtained. To finish, conclusions are presented followed by a discussion suggesting future research directions.

Introduction

Over the past few decades, the role of supply chain (SC) has been evolving from cost centre to competitive advantage. The International survey "Global supply chain survey 2013", led by PwC group, show that companies acknowledging SC as a strategic asset generate a 30% increase of profitability compared to the average (around 500 completed questionnaires from various industry sectors). Equally according to [START_REF] Kaihara | Supply chain management with market economics[END_REF], supply chain management (SCM) is now recognised as one of the best means by which enterprises can make instant improvements to their business strategies and operations. Thus today's competition has shifted from inter-company level to intersupply chain level [START_REF] Burgess | Supply chain management: a structured literature review and implications for future research[END_REF][START_REF] Lambert | Supply chain management: processes, partnerships, performance[END_REF][START_REF] Lummus | Defining supply chain management: a historical perspective and practical guidelines[END_REF][START_REF] Mentzer | Fundamentals of Supply Chain Management: Twelve Drivers of Competitive Advantage[END_REF]. Absolute growth lever of companies, SC formerly simple and linear, is nowadays considered as a complex system [START_REF] Surana | Supply-chain networks: a complex adaptive systems perspective[END_REF]. Although there are no generally accepted definitions of SC, in coherence with the perimeter of this paper the following definition is taken on: "A supply chain consists of all parties involved, directly or indirectly, in fulfilling a customer request. The supply chain includes not only the manufacturers and suppliers, but also transporters, warehouses, retailers, and even customers themselves. Within each organisation, such as a manufacturer, the supply chain includes all functions involved in receiving and filling the customer request. These functions include, but are not limited to, new product development, marketing, operations, distribution, finance and customer service" [START_REF] Chopra | Supply chain management: strategy, planning, and operation[END_REF]. Besides, today's environment is more dynamic [START_REF] Kaihara | Supply chain management with market economics[END_REF] and SC have to satisfy regulatory requirements (societal pressures for example) and profitability requirements (financial, flexibility, competitiveness…). That is why during the last few decades focusing on factory level management has been replaced by firm level management of SC [START_REF] Gunasekaran | Performance measurement and costing system in new enterprise[END_REF]. SC being considered as a key factor of corporate success [START_REF] Estampe | A framework for analysing supply chain performance evaluation models[END_REF], measurement and management of SC performance become essential. Nevertheless, such an undertaking is complex due to the transversal characteristic of these processes, involving numerous actors having to cooperate in order to reach given strategic objectives.

Therefore, the purpose of this paper is to review at what stage big size companies are about SC performance measurement and management concepts, highlight their current practices and the related main issues they have to cope with. To do so, a benchmarking study has been carried out, based on data collected through interview process from eleven multinational companies. The rest of the paper is organised as follows. The next section presents a literature review focusing on benchmarking survey dealing with SC performance measurement and management or related topics. Section 3 describes our empirical analysis, detailing the sample, the methodology used to collect and analyse data and preliminary results obtained. To finish Section 4 presents a discussion and conclusions.

Overview of the Published Benchmarking Studies

In this section, a literature review is established on benchmarking survey dealing with SC performance measurement and management concepts, or related topics.

Benchmarking is a well-known process aiming to improve performance by learning from the best performers in the class [START_REF] Fong | Benchmarking: a general reading for management practitioners[END_REF]. In this paper, the idea is to carry out such a comparative analysis, in order to observe the practices of several companies in the area of measurement and management of SC performance. This part aims to position the present benchmarking and the published benchmarking studies on a common framework described hereinafter. [START_REF] Bhutta | Benchmarking -best practices: an integrated approach[END_REF] introduced a matrix composed of two types of components. The first one answers the question: "What is benchmarked?" Three options are possible: Performance -how good performance is compared to others, Process -methods and processes used to improve organisational effectiveness and Strategic -changes in strategic directions and decisions. The second one answers the question "What to benchmark against?" It could be Internal -within the organisation, Competitor -within industry/sector, Functional -technology and techniques used, Generic -best practices from any sector or industry.

Only external benchmarking studies are reviewed in this paper, giving it is the type of the present benchmarking study detailed in section 3. Indeed, by definition, internal benchmarking studies deal with comparison of processes or operations within an organisation only. In this type of benchmarking, the acquisition of information is facili-tated. However, information obtained can be shortened and/or oriented, each one wanting to protect the interest of its department or its own.

In the literature review, two kind of benchmarking studies can be distinguished: 1-Benchmarking launched in order to validate a framework built, 2-Benchmarking studies without framework to validate.

Benchmarking Aiming to Validate a Framework Previously Developed

The literature review shows that usually benchmarking process is used in order to validate a framework previously developed. For instance, [START_REF] Li | Development and validation of a measurement instrument for studying supply chain management practices[END_REF] conceptualized, developed, and validated six dimensions of SCM practices (strategic supplier partnership, customer relationship, information sharing, information quality, internal lean practices, and postponement) using data collected from 196 manufacturing firms. [START_REF] Bayraktar | A causal analysis of the impact of information systems and supply chain management practices on operational performance: Evidence from manufacturing SMEs in Turkey[END_REF] has empirically tested a framework identifying the causal links among SCM and information systems (IS) practices, SCM-IS related inhibiting factors and operational performance based on a sample of 203 manufacturing Small and Medium Enterprises (SMEs) within the greater metropolitan area of Istanbul in Turkey. Equally in manufacturing industry, [START_REF] Algren | State of the art of supply Chain performance measurement in Danish industrial companies[END_REF] examined which dimensions are used by the largest Danish companies to measure supply chain performance measurement (SCPM) at operational, tactical and strategic level, how can these dimensions be classified, and how do these empirical results have implications for practice and selected SCPM-theories.

The SCPM model they proposed has been theoretically developed and empirically validated. In the airline and airport field, [START_REF] Barros | An evaluation of European airlines' operational performance[END_REF] applied a two-step Data Envelopment Analysis (DEA) procedure to evaluate the operational performance of a sample of the Association of European Airlines, whereas [START_REF] Schmidberger | Ground handling services at European hub airports: Development of a performance measurement system for benchmarking[END_REF] developed a holistic performance measurement system (PMS) for airport ramp service providers with a process-based perspective, and conducted a benchmarking study in several European hub airports. The authors followed the action research approach for defining the PMS, which associates weights to the measures in an Analytical Hierarchical Process, and grouped measures into the perspectives of the Balanced Scorecard.

Benchmarking Studies without a Framework to Validate

In the transport logistics context of Hong Kong, [START_REF] Lai | An empirical study of supply chain performance in transport logistics[END_REF] conducted a benchmarking study considering efficiency (economic use of resources) and effectiveness (fulfilment of customer requirements) measures. The 134 responses obtained allowed to evaluate their perceived SC performance in transport logistics from both cost and service perspectives. On the other hand, without specific context, in order to justify that leadership behaviour measurement can and should be part of any performance measurement system, [START_REF] Kulmala | Performance through measuring leader's profiles: An empirical study[END_REF] gathered exploratory empirical data from 11 Finnish SMEs located in Western Finland. Another kind of topic, investigate what relevant forecasting variables should be considered to improve companies' performance. [START_REF] Danese | The impact of forecasting on companies' performance: Analysis in a multivariate setting[END_REF] analysed equally whether some forecasting variables can interact and influence performance with a synergistic effect by means of data collected by the Global Manufacturing Research Group from a sample of 343 manufacturing companies in 6 different countries.

According to [START_REF] Basnet | Benchmarking supply chain management practice in New Zealand[END_REF], while there is plenty of published literature that explains or espouses SCM, there is a relative lack of empirical studies examining SCM practices. [START_REF] Basnet | Benchmarking supply chain management practice in New Zealand[END_REF] report the current status of SCM of manufacturing organisations in New Zealand. The outcomes suggest that although there is awareness of the SCM concept in New Zealand, the adoption of the newer concepts of SCM is not very advanced. [START_REF] Quayle | A study of supply chain management practice in UK industrial SMEs[END_REF] surveyed SCM practices in UK, collecting data from 288 industrial SMEs. The findings indicate a lack of effective adaptation from traditional adversarial relationships to the modern collaborative "e" -supply chain and also identifies issues businesses need to address to improve the performance of their supply chains. Similarly, [START_REF] Tan | Supply Chain Management: Practices, Concerns, and Performance Issues[END_REF] investigated practices and concerns of SCM in United States and concluded that all of significant SCM practices positively impact performance. Still about SCM practices but this time in Finland, [START_REF] Kemppainen | Trends in industrial supply chains and networks[END_REF] interviewed managers of six SC in order to analyse the change of SCM both in terms of operational practices and organisational capabilities. Some papers focus on metrics, as [START_REF] Gunasekaran | A framework for supply chain performance measurement[END_REF] which compared key performance indicators (KPIs) importance of 21 British companies or the collaborative survey [START_REF] Salmon | Agora du Supply Chain Management: Supply chain -Quels KPIs pour les managers[END_REF] aiming at highlight KPI's use and consistency with companies' needs in France. While others are concentrated on process perspective, for instance [START_REF] Neely | Performance measurement system design: Should process based approaches be adopted?[END_REF] analysing the use of structured processes for the design of PMS in the UK (around 350 SMEs from a variety of industries) and [START_REF] Bhagwat | Performance measurement of supply chain management: A balanced scorecard approach[END_REF] finding out about how SMEs in India apply Balanced Scorecard concept by the combination of three case studies and semi-structured interviews. The literature includes research works about strategy perspective as well. [START_REF] Sahay | Supply chain management practices in Indian industry[END_REF], using a representative sample of 156 organizations mostly from manufacturing, discuss SC strategies and structures in India whereas [START_REF] Chin | A study on supply chain management practices: The Hong Kong manufacturing perspective[END_REF] conduct a survey that examines the success factors in developing and implementing SCM strategies for Hong Kong manufacturers. Finally, [START_REF] Estampe | Benchmark de la supply chain[END_REF] compare performances of 68 European enterprises based on 5 KPIs from Supply Chain Operations Reference (SCOR) model, calculated using data from enterprise financial review.

To conclude, each of these studies are positioned in an adaptation of the matrix proposed by [START_REF] Bhutta | Benchmarking -best practices: an integrated approach[END_REF] in table1 presented below. Two main observations can be raised.

Table 1. Positioning of the studies reviewed on an adaptation of the [START_REF] Bhutta | Benchmarking -best practices: an integrated approach[END_REF] matrix What to benchmark against?

What is benchmark?

Competitor Functional Generic Performance [START_REF] Barros | An evaluation of European airlines' operational performance[END_REF][START_REF] Schmidberger | Ground handling services at European hub airports: Development of a performance measurement system for benchmarking[END_REF][START_REF] Lai | An empirical study of supply chain performance in transport logistics[END_REF] [19] [START_REF] Estampe | Benchmark de la supply chain[END_REF] Process [START_REF] Bayraktar | A causal analysis of the impact of information systems and supply chain management practices on operational performance: Evidence from manufacturing SMEs in Turkey[END_REF] [14], [START_REF] Basnet | Benchmarking supply chain management practice in New Zealand[END_REF] [12], [START_REF] Kulmala | Performance through measuring leader's profiles: An empirical study[END_REF], [START_REF] Quayle | A study of supply chain management practice in UK industrial SMEs[END_REF], [START_REF] Kemppainen | Trends in industrial supply chains and networks[END_REF][START_REF] Gunasekaran | A framework for supply chain performance measurement[END_REF][START_REF] Salmon | Agora du Supply Chain Management: Supply chain -Quels KPIs pour les managers[END_REF][START_REF] Neely | Performance measurement system design: Should process based approaches be adopted?[END_REF][START_REF] Bhagwat | Performance measurement of supply chain management: A balanced scorecard approach[END_REF]] Strategy [START_REF] Sahay | Supply chain management practices in Indian industry[END_REF][START_REF] Chin | A study on supply chain management practices: The Hong Kong manufacturing perspective[END_REF] First, obviously, there is an empty square at the intersection between strategy and competitor because for a start it is quite difficult to convince long term partners of an organisation to adopt this approach thus it seems even more unattainable to obtain competitors approval for such a partnership. Similarly, it is empty at the intersection between strategy and generic, as it seems to have little interest to compare strategy of companies from various industries. Moreover, by definition, strategy cannot be imi-tated. Secondly, by contrast, the majority of the studies are placed at the intersection between process and generic as the present benchmarking study. However, there is a difference among these eight research works in the way to collect data. Six [START_REF] Li | Development and validation of a measurement instrument for studying supply chain management practices[END_REF], [START_REF] Kulmala | Performance through measuring leader's profiles: An empirical study[END_REF], [START_REF] Quayle | A study of supply chain management practice in UK industrial SMEs[END_REF], [START_REF] Gunasekaran | A framework for supply chain performance measurement[END_REF][START_REF] Salmon | Agora du Supply Chain Management: Supply chain -Quels KPIs pour les managers[END_REF][START_REF] Neely | Performance measurement system design: Should process based approaches be adopted?[END_REF] use questionnaires whereas [START_REF] Bhagwat | Performance measurement of supply chain management: A balanced scorecard approach[END_REF] use semi-structured interviews then case studies and [START_REF] Kemppainen | Trends in industrial supply chains and networks[END_REF] lead interviews. Another distinction between the "processgeneric" benchmarking is the size of enterprises considered. Half of them concentrate only on SMEs ( [START_REF] Kulmala | Performance through measuring leader's profiles: An empirical study[END_REF], [START_REF] Quayle | A study of supply chain management practice in UK industrial SMEs[END_REF], [START_REF] Neely | Performance measurement system design: Should process based approaches be adopted?[END_REF][START_REF] Bhagwat | Performance measurement of supply chain management: A balanced scorecard approach[END_REF], two [START_REF] Li | Development and validation of a measurement instrument for studying supply chain management practices[END_REF], [START_REF] Salmon | Agora du Supply Chain Management: Supply chain -Quels KPIs pour les managers[END_REF] include SMEs as well as large companies and the two remaining [START_REF] Kemppainen | Trends in industrial supply chains and networks[END_REF][START_REF] Gunasekaran | A framework for supply chain performance measurement[END_REF] focus on large companies.

As the literature review highlights it, there is a lack of survey collecting data through interview process and especially addressed to large companies and their related research in the area of SC performance. This is the bias of the present paper.

Empirical Analysis

The sample constructed referred to 11 multinational corporations which employ by far more than 5000 people. Three of them are Native American companies and the 8 others are French companies. The sectors represented are Fast-Moving Consumer Goods (FMCG), Household appliance, Automotive, Luxury, Distribution and Steel industry. The selected companies represent also different geographical locations in France as well as have SC management differently organised. The aim of our undertaking is mainly to highlight current practices in today's large companies, understand the principal trends and identify correlations regarding concepts of measurement and management of SC performance.

Method to Collect Data and Data Analysis

We met each company twice and led interviews of about two hours based on a previously developed questionnaire in order to guide the discussions. All interviews were held at the respective companies' office, which allows insuring an environment conducive to obtain information easily even the sensitive ones. Two or three persons per company have been interviewed. Respondents met are SC directors, with a national or worldwide perimeter and/or internal SC experts. The first step to analyse data was to choose adequate comparison criteria. Further to interviews, we selected 11 coherent criteria from five key aspects: from SC organisation aspect (chain perimeter, process perimeter, group organisation), from measurement aspect (number of KPIs, shared KPIs), from management aspect (who define KPIs, who set KPIs' targets, who manage in the sense of reaching objectives, management tools), from performance aspect (type of performance measured), and the last criterion but not the least, is about company performance culture. Indeed, the enterprise culture is rarely taken into account in benchmarking studies while it is an important factor which influenced decision-making in general. As interviews were rich in information, it was primordial to find a way to make the data comparable. To do so, we built synthetic profile of each company. We will not go into further detail in this article. The following section shows the preliminary results obtained.

Preliminary Results

First, there is a tendency to have many KPIs, more than 20 in 45% cases, which participate to the complexity of PMS. Clearly, the number and the choice of KPIs is still a problematic. The assessed performance remains predominantly economic, although we note ongoing project to evaluate environmental (36%) and social (28%) performance. Indeed, not only increasing societal pressures have an effect but also companies become more and more aware of the performance potential which could be resulting. Due to incomplete information about shared KPIs we feel inadequate to draw conclusions; however we can notice a difficulty to answer to that question which highlights a lack of visibility of what is shared with whom. The definition of KPIs for the most part occurred in centralized SC (45%), which has the advantage to insure homogeneity of KPIs set of SC sites. Decision about KPIs' targets is also handled by central SC (36%) in order to align overall objectives, i.e. strategic objectives, with SC sites objectives. On the other hand, local SC (64%) managers are in charge of performance management through KPIs. In that, we detect the general wish to manage SC performance as closely as possible to the field. Regarding SC culture, of course influenced by corporate culture, the following key messages are conveyed: get unquestionable KPIs, get less KPIs more standardized, get a wide vision of performance, simplify PMS, simplify reporting process, share more widely, measure collaborators performance, be committed. Today's companies direct their efforts toward simplification, collaboration based on a common language and commitment. Results about tools used will not be presented in this article.

Three correlations can be raised. First, B-to-B companies are organized by global business unit; have a process perimeter extended in comparison with B-to-C companies and make measurement system reviewed by central SC. On the contrary, B-to-C companies are organized by geographical zone and revise measurement system locally. Finally, in the majority of cases (80%), KPIs' targets setting process and performance management process, in the sense of manage through KPIs, are owned by the same level (local/local or central/central). However, we note two exceptions from this observation. KPIs' targets are set by local SC and the reaching of targets is managed by central SC. We understand that people from SC sites have a better knowledge of the field to choose ambitious targets but above all attainable ones. The second exception describes the opposite case, KPIs' targets set by central SC and management to reach targets owned by local SC. We explain it by the fact local SC as we said previously have a better knowledge of the field and thus are the most likely to make the objectives achieved.

Conclusions and discussion

As the literature review highlights it, there is a lack of survey dealing with measurement and management of SC performance and especially which collect data through interview process and addressed to large companies. This is the bias of the present paper. We studied the current SC performance measurement and management practices of multinational corporations established in France. In this way, we cover a rea-sonable spectrum of firms from varied businesses. We highlighted, on one hand, measurement current tendencies as the density of measurement systems and type of performance measured in fact. On the other hand, we raised performance management current tendencies as KPIs definition, targets setting and performance management processes' decision levels in the SC. We also showed correlations illustrating B-to-B and B-to-C companies' profiles. We underlines that there is coherence between KPIs definition process and targets setting process being owned by the same decision level.

With this survey, we contribute with new findings that have implications for theory and offer to practitioners an up to date point of comparison. We proposed a cartography positioning published benchmarking studies, concerning several sectors, related to the SC performance issue according to the type of benchmarking. Moreover, through results, we delivered an overview of the state of progress of large companies regarding current key problematic.

Nevertheless, we present only a snap-shot view of the topic. First of all, a clear limitation to our study is the size of the sample. As we choose to proceed by interviews it would be difficult to drastically increase the number of companies to meet. Thus we can consider this study as an explorative one and not fully representative of the whole population. Besides, we collected data from SC directors and internal SC experts. It could be interesting to analyse the perceptions from other members of the SC or collaborators, such as suppliers or customers' points of view.


Manuel Rippel
email: mrippel@ethz.ch

Jost-Wolfram Budde

Felix Friemann

Paul Schönsleben

Building blocks for volume-oriented changeability in personnel cost structure of manufacturing companies

Keywords: Flexibility, Volatility, Volume-oriented Changeability, Personnel

Volatilities in global markets lead to rising importance of volumeoriented changeability (VoC) in the manufacturing industry. If the production demand is fluctuating, manufacturing companies often struggle to adapt their overhead costs, which are causing high variances in unit costs. Personnel is a main cost driver in overhead cost structure, in particular in high-wage countries. Therefore, this paper conceptualizes building blocks and analyzes impact relations for configuring VoC in personnel cost structure in production plants.

Introduction

Nowadays, companies are facing uncertainty in global markets as an omnipresent condition. For that reason, Wiendahl et al. introduced the concept of changeability as a system's potential to conduct technological, logistical, organizational and personnel changes beyond the available system-inherent flexibility corridors by means of an acceptable effort [START_REF] Wiendahl | Changeable Manufacturing -Classification, Design and Operation[END_REF]. In particular manufacturing companies have to configure their capacities and capabilities in their production plant under the uncertainties of high volatility of order volumes [START_REF] Raturi | Creating a volume-flexible firm[END_REF]. Therefore, they are forced to find ways to economically adapt their cost structure to the fluctuating production volume, since manufacturing costs are highly sensitive due to fixed cost component [START_REF] Wildemann | Fixkostenmanagement -Leitfaden zur Anpassung von Kostenstrukturen an volatile Märkte[END_REF]. Rippel et al. introduced the concept of "volume-oriented changeability" (VoC) focusing on the change dimension "volume", expand existing considerations of changeability to an socio-technical perspective and include indirect aspects in the plant environment [START_REF] Rippel | Profiling as a means of implementing volume-oriented changeability in the context of strategic production management[END_REF]. This is particularly important, since around 50% of employees are working in support processes and their cost structure mainly consists of fixed costs [START_REF] Remer | Einführen der Prozesskostenrechnung: Grundlagen, Methodik, Einführung und Anwendung der verursachungsgerechten Gemeinkostenzurechnung[END_REF]. Interdependencies of instruments, numerous influencing factors and general conditions, such as restrictive labor legislations, limitations due to social appropriateness and compliance with corporate cultural values, complicate the configuration of VoC of personnel cost structure [START_REF] Letmathe | Capacity management under uncertainty with inter-process, intra-process and demand interdependencies in highflexibility environments[END_REF]. Thus, the objective of this paper is to conceptualize building blocks for VoC and analyze their impact relations in order to support plant management to preventively set-up a holistic package with ready-to-use instruments for adapting personnel capacity and influence associated personnel costs.

The findings have been developed through literature studies and interviews with three manufacturing companies from two industries (automobiles & parts, industrial goods & services). In addition, insights and findings were embedded, which were gained within the design and implementation of VoC at four production plants of a case study company (construction & materials, personal & household goods).

The multitude of existing obstacles reveal the need to systematize categories as building blocks for enhancing transparency and facilitating a basic configuration. The following questions will be answered: (1) Which decisive categories of enablers and levers do exist? (2) Which main influencing variables and impact relations have to be considered? (3) How does the combination of the building blocks look like?

2

Conceptualizing building blocks

This section presents the findings of the conducted case studies by conceptualizing building blocks as aggregated categories of instruments and design elements (see Fig. 1). It is intended to cover the most relevant topics but not to be exhaustive. The formalization differs from classical considerations, since the decisive factor of the category scheme is the mechanism contributing to VoC. Some instruments have a direct influence on the fields of impact, whereas some others indirectly affect them.

The building blocks can be distinguished in "Enablers", which comprise the prerequisites for the set-up and execution of instruments, and in "Levers", which systematize instruments according to their impact mechanism.

Enablers

The enabler "work organization" provides the framework for the working-timesystem, staffing levels, autonomous work groups as well as the organizational design of the system regarding structure and process organization. Depending on the design, the work organization itself provides flexibility potential or the requirements for the use of certain flexibility instruments. Thus the work organization can be seen as a condition or as an object of flexibility measures [START_REF]Wandlungsfähige Produktionssysteme -Heute die Industrie von morgen gestalten[END_REF]. Work organization provides system-inherent capacity leeway by introducing employee-related instruments (e.g., job rotation, home office) and measures that increase the employability, which define the qualification for flexible workforce deployment with regard to shifting of capacities. Various measures of employability can be distinguished according to [START_REF]Employability Management: Grundlagen, Konzepte, Perspektiven[END_REF]. In addition to employee-related measures, such as improving workforce flexibility, career models and health promotion, there are also business-related measures, which focus on the change management style or changes in corporate culture and organizational structure. Besides, the work organization also facilitates instruments in the value chain (e.g., extended work bench) by reorganizing tasks for execution by third parties and establishing interfaces with external partners. The enabler "arrangement" includes formalities related to the position, location and duration of working-time. Within the design of internal arrangements (e.g., labor contracts, agreements with work councils) the possible use of flexibility measures must be taken into account [START_REF] Armutat | Flexibilitätsorientiertes Personalmanagement: Grundlagen, Handlungshilfen, Praxisbeispiele[END_REF], e.g. scope of employment, periods of notice and contracts with for a limited period of time. Working-time flexibility can also be supported by clauses for additional or reduced working-time (e.g., employment leveling). The precise and transparent definition of rules and standards as well as trigger points and escalation levels for the activation of measures will enable mutual understanding and acceptance of both employees and employer. Employees benefit from minimized uncertainty with regards to the further approach. The employer benefits from a prealigned and prepared set of measures, which significantly increases the scope and speed of action in case of unforeseen demand fluctuations.

The enabler "time accounts" consists of working-time accounts, which are used to decouple contractual working hours and actual operated work. Working-time accounts are not independent models, but are often required as a basis for using working-time models. The combination of different types (e.g., work-time account, saving account, life-work-time account), their individual purpose and their interaction enable the implementation of various instruments by means of providing a reserve of work hours as "breathing volume". Thereby, position and duration of operated work can be adapted, when the demand differs from the contractual work time as regular baseline. Fig. 1. Enablers and levers within value chain and system-inherent design.

Levers

The lever "worktime / shift-modeling" consists of flexible working-time models (e.g., trust-based work time, flextime) and options to adapt the shift-model (e.g., shortening/extensions, additional shifts, holidays and weekends). Instruments of this block change the duration and the position of working-time. The lever "remuneration scaling" defines ways of remuneration contributing to VoC. Roughly they can be divided into fixed salary, bonuses or flexible wage components. They must include a demand-oriented component instead or in addition to the common performance-oriented components.

The lever "employment leveling" comprises instruments to adapt the contractual working hours and thereby the capacity baseline, which couples the personnel expenditures (both direct and indirect labor costs), operated work and capacity demand. For example, a contractually regulated time-corridor defines which working-time must be fulfilled by the employee in case of deviations from the contractual workinghours. Thereby, the corridor can be used to extend or shorten working-time and time used within the corridor can be accounted on a working-time account. To provide a cash-effective capacity flexibility the accounting balance of the corridor can be determined with an effect on the remuneration. In that case a debt on the working-time account means a reduction of remuneration for the employee. The instrument "basis adjustment" can provide further system-inherent potential by means of an adaptation of working-time-related contractual components. It describes the possibility to adjust the time-corridor or the contractual working-hours after a certain contractual period.

The lever of "deployment shifting" consists of measures for flexible workforce deployment. The area of application of the flexible employee may be beyond department employee pools, plant-wide, company-wide or beyond the corporate boundaries [START_REF] Bazenski | Flexibilität in Unternehmen der Metall-und Elektroindustrie[END_REF]. Utilization deviations between working-groups or production units can be balanced by horizontal shifting of trained employees. Furthermore, multi-skilled employees from indirect functions can extend production capacity. In particular a combination with temporary workers provides impact potential. For instance, in case of a decline of production output, the capacity of temporary workers in production units can be disproportionately reduced. The gap can be filled by vertical shifting of employees from indirect areas. Features to be determined are the duration of use which can be predetermined or demand-oriented. Features that describe capacitive impacts are the need for training the employee or the employee's productivity to perform nonspecialist tasks. Apart from that, remuneration models should be adapted according to the qualification requirement of the task or to working-time duration.

The lever "baseline adaption" is differentiated from other system-inherent building blocks, since it determines the baseline of internal personnel resources. An increase (or decrease) implies that new resources are brought inside the system from the outside (and vice versa). Therefore, these instruments are indirectly considered as system-inherent. Furthermore, the changes of internal capacity and associated cost level are relatively static (e.g., hiring, dismissal) and partially non-reversible (e.g., early retirement). The impact of the instruments is discrete and fairly long-term, whereby incremental and continuous adaptations prove to be difficult.

The lever "external partnering" contains options within the value chain to cover capacity demands. The design of the contract is crucial for utilizing external partnering as a VoC instrument, since the type of commitment allows adapting both capacity and associated payments: Firstly, the provision of service or capacities can be fixed by contract or aligned to the current demand. Thereby, the VoC potential depends, among others, on the period of notice, guaranteed purchase quantities, degree of risk participation by means of compensation payments in case of shortfall of minimum quantities [START_REF] Wildemann | Fixkostenmanagement -Leitfaden zur Anpassung von Kostenstrukturen an volatile Märkte[END_REF] or the option of recurring basis adaptation of agreed services during the contract period in flexible intervals. Secondly, the cost model defines if the service should be considered as fixed or variable cost. In case of lump-sum contracts the fixed cost lead to a high operating leverage. This causes a deterioration of profitability in periods of demand decline [START_REF] Wildemann | Fixkostenmanagement -Leitfaden zur Anpassung von Kostenstrukturen an volatile Märkte[END_REF]. If the payments depend on the amount of delivered services, the cost structure varies and is in line with the demand. Thirdly, it is important for a demand-oriented dimensioning of the service to compare the performance (e.g., productivity) of external capacity with internal resources.

Analyzing impact relations

The building blocks have impacts in technical, financial and social dimensions. In the following the individual, basic leverage effects on the most relevant fields of impact are displayed (see Fig. 2). Nevertheless, their existence, direction and extent depend on influencing variables, which are introduced initially.

Fig. 2.

Building blocks, influencing variables and fields of impact.

Influencing variables

The influential variable "control" has a crucial role in the process of configuring the building blocks, since the VoC potential of each measure strongly depends which stakeholder has which rights related to each measure. For example, the VoC potential of an employee-controlled working-time account significantly differs from an employer-controlled working-time account. The rights can be distinguished in decision and disposition right. The decision right determines a party's right to decide whether a measure is performed or not. The scope and timing of the measure are determined by the party with the disposition right [START_REF] Schmidt | Betriebliche Strategien der Flexibilisierung: die Rolle der Arbeitszeit[END_REF][START_REF] Som | Flexibilität und Stabilität in Betrieben des deutschen Verarbeitenden Gewerbes[END_REF]. These rights can be hold by the employee, employer or both. "Price" involves the fact, that most instruments entail costs, since the risk of underutilized capacities is allocated to another party (e.g. employees or external partners). This party will demand a risk premium [START_REF] Rippel | Profiling as a means of implementing volume-oriented changeability in the context of strategic production management[END_REF]. "Agility" underlines the importance of the temporal dimension, e.g. the required time to implement or to exploit the potential of a measure. The variable "duration" describes the duration of working-time in a given period and "position" comprises, when the work is conducted during a period. "Location" determines, where the task is performed, e.g. at another production unit or another plant.

Fields of impact

The primary field of impact is personnel "capacity", which must be provided in the necessary quantity at the right time at the right place with the required capability. Thereby, the building blocks are contributing to delivery reliability and high utilization. The field "capability" is considered, since instruments can affect the organization's know-how, which is indirectly related to the company's performance in the long-term. The financial implication of the building blocks requires to distinguish "Profit & Loss-Effectiveness" (P&L) and "Cash-flow-Effectiveness". The P&L-Effectiveness contributes to keep the variances of product cost stable despite of demand fluctuations. Nevertheless, the Cash-Flow-Effectiveness is of major relevance, since it also affects the cash-flow. The difference can be illustrated by looking at the lever "Worktime / Shift-Modeling": The required capacity can be provided by adapting the amount of working hours. Thereby, the performed working hours differ from the regular working hours, which are stated in the contract. The deviation between performed and contractual working hours is recorded in a time account. Furthermore, the performed working hours are solely booked as personnel costs in the Profit-&-Loss statement (P&L-effective). Nevertheless, the employees receive the same payments each month according to the contractual working hours and independent from the performed working hours, respectively the capacity requirements. This implies that the cash-flow of the organization remains unaffected, which could cause liquidity shortages in a long-lasting crisis. Particular instruments leverage the field "employee satisfaction", if they have participation options, e.g. decision and disposition rights with regards to duration and position of work-time or adjustments of employment level depending on the individual phase of life. This results in higher motivation, which can also increase the quality or productivity of their work [START_REF] Schulte | Personal-Controlling mit Kennzahlen[END_REF]. The company can also enhance its "employer attractiveness" on the job market, if employee's needs are addressed in the design of the work-time system [START_REF] Blum | Praxishandbuch Arbeitszeitmanagement: Beschäftigung durch innovative Arbeitszeitmodelle[END_REF].

Combining impact potentials

Changeability in working-time-systems is usually determined by the possibility of a structural adaption to changing requirements [START_REF] Kinkel | Wandlungsfähigkeit messen und benchmarken[END_REF]. The VoC potential in the scheme of the building blocks is exemplarily illustrated in Fig. 3 The combination of various building blocks results in increasing flexibility corridors and VoC potentials. It becomes apparent, that some instruments just enhance the potential with regards to capacity but do not affect the ability to adapt the corresponding cash-flow. This is crucial important for maximizing the ability to handle volume fluctuations economically. System-inherent instruments with an impact on cash-flow (e.g., employment leveling) are demanding a lot from employees, since their salaries are adapted. Instruments within external partnering enable to avoid the impact for internal employees. It is social reasonable to set up this potential in growth phases.

The concept provides guidance for practitioners within VoC in personnel capacities. A holistic package of ready-to-use instruments can be preventively implemented to increase the potential to act in volatile business environments. Thereby, responsiveness, speed and commensurability of actions as well as the transparency of associated impacts for both management and employees can be increased significantly. The benefits consist in the capability to adapt the personnel cost structure and associated multi-dimensional key performance indicators. The economic implications can be derived from the comparison of costs and benefits of the instruments.

Conclusion and outlook

The building blocks provide companies a comprehensive overview of relevant design fields, which should be considered to use leverage effects. The concept gives direction to conduct a first basic configuration on strategic level. This creates the foundation for further dimensioning and detailing. The novelty lies in the provided transparency with regards to the scope, categories and impact relations of the various existing instruments. Decision-makers are enabled to consider multi-dimensional implications. Additionally, the distinction between P&L-effective and cash-flow-effective impact implies an aspiration level with regards to changeability, which is beyond the common focus in existing literature.

Limitations exist in the limited number of selected decisive influencing factors and fields of impact in order to make the scheme applicable for practical use on strategic level. In a next step, a simulation model is required for dimensioning the building blocks. The simulation of the working-time-system's behavior regarding the impact and interdependencies of the building blocks can be used to display fundamental effects on capacity and costs before starting implementation of VoC in the company. In addition, an appropriate and reasonable balance between technical, financial and in particular social aspects has to be considered.

Fig. 3 .

 3 Fig. 3. Exemplary combination of impact potentials from a technical and financial perspective.