Y Ming
email: yue.ming@enit.fr

R Houe Ngouna

B Grabot

"Performance, interoperability and safety for sustainable development" MODELS FOR SUPPLY CHAIN NEGOTIATION IN COLLABORATIVE RELATIONSHIPS

Keywords: supply chain, collaboration, negotiation, risks

Nowadays, firms are increasingly building collaborative relationships with their partners in order to improve the global performance of the supply chain in which they are involved. Such collaborative relationships require information exchange or share and negotiation. In this paper, we first formalize some practices of collaboration from case studies of the aeronautical area then suggest some models for negotiation, allowing a supply chain member to publish hidden constraints and share risks/costs in order to achieve a win-win situation.

INTRODUCTION

In collaborative supply chain, the conflicts between autonomy and collaboration in one hand, local interest and global objectives in the other hand, are important problems the supply chain members are currently facing, especially when involved in multiple networks. Furthermore, the growing uncertainty on the customers' demand makes the supply chain harder to manage. In this context, it is usually considered that an increased collaboration is a good way to minimize the risks linked to this uncertainty [START_REF] Hallikas | Risk-based classification of supplier relationship[END_REF]. Firms are so building collaborative relationships with their supply chain partners in order to achieve efficiency, flexibility, and competitive advantages [START_REF] Nyaga | Examining supply chain relationship: Do buyer and supplier perspectives on collaborative relationship differ[END_REF].

We suggest in this communication a series of models of negotiation between customer and supplier, which helps to publish hidden constraints, synchronize internal and external interests and share risks with supply chain member in a context of collaborative relationships.

COLLABORATIVE RELATIONSHIP IN A SUPPLY CHAIN

Many studies suggest that collaborative relationships are associated with the improvement of the supply chain performance. [START_REF] Kalwani | Long-term manufacturer-supplier relationships: do they pay off for supplier firms[END_REF] noted that manufacturers seek for long-term relationships with fewer suppliers in order to secure valued resources and technologies, master supplier skills and strengths, and gain from quality and process improvements. [START_REF] Holland | Cooperative supply chain management: the impact of interorganisational information systems[END_REF] has shown that companies are moving towards collaborative relationships in an effort to make the supply chain as a whole more competitive. [START_REF] Maloni | Supply chain partnerships: opportunities for operations research[END_REF] suggest that it is essential for a firm's survival to have collaborative relationships with its suppliers. [START_REF] Chung | Building co-operative supply chain in auto parts manufacturing industry[END_REF] express the idea that an interesting way to build an efficient supply chain is to integrate the supply chain activities by developing collaborative relationships between firms. [START_REF] Daugherty | Is collaboration paying off for firms[END_REF] found that firms engaged in collaborative relationships achieved improved visibility, higher service levels, increased flexibility, greater end-customer satisfaction, and reduced cycle times.

However, the real collaboration practices seem to be more complex to implement than considered in the literature. Considering practical cases, we have analyzed the behaviors resulting from collaborative relationships in the aeronautical industry. This study, along with associated results, is described in the following.

EXAMPLE OF PROBLEMS IN COLLABORATIVE RELATIONSHIPS: FROM THEORY TO REAL SITUATIONS

The case studies considered here are based on projects launched within the federative structure IODE 1 , aiming at analyzing collaboration in supply chains, among which one performed with funding from an association of companies of the aeronautic sector and from a public body interested in SMEs development. The objective of the project was to analyze the problems linked to the collaboration between partners of aeronautical supply chains, especially when SMEs are involved. The people in charge of the relationship with customers and suppliers of twenty companies have been interviewed in that purpose, the panel being composed of 7 large companies and 13 of middle (around 200 employees) or low (less than 100 employees) size.

1 IODE is a group of researchers in Industrial Engineering in the South West of France (http://idce.enit.fr/iode/)

In a decentralized supply chain (e.g. when no central planning is performed), a cascade of ERP systems is usually considered as a mean to coordinate partners. MRPII (Manufacturing Resource Planning), the core production model of an ERP system, is usually used to perform and organize planning during supply and demand processes, including sharing information at different levels of operation plans and purchase orders.

As seen in Figure 1, forecasts based on the expected customer's demand are built by the focal company of the chain (usually the final assembler in the aeronautical sector) then processed using the MRPII principles. After the MRP (Material Requirement Planning) step, planned orders/forecasts are grouped in a supply plan, sent to the tier (n+1) partners (see the left and middle side of the figure).

Figure 1. Supply chain planning using a cascade of MRP processes

When analyzing the implementation of these processes through interviews, some problems were identified, especially related with SMEs (see [START_REF] Ming | Models for customer-supplier negotiation in a collaborative supply chain[END_REF] and (Affonso, 2008) for more details). In this paper, we will focus on some specific problems showing that real situations are more complex than the basic framework of Figure 1. The gaps, which are usually hidden, might lead to poor performance in the collaboration within the supply chain.

• Problems linked to the firm period of the forecasts

The first issue identified during the interviews is that the size of the firm period of the forecasts may be inconsistent with the supply lead times. As an example, a relative scarcity of some aeronautical alloys together with a lack of capacity of companies providing casting parts made that the supply time of raw materials increased up to 12 months in some cases. In spite of this, the firm period of the forecasts sent by the customer to their suppliers remained constant, around 3 months, compelling the suppliers to take the risk to order materials on the base of flexible forecasts, or to be late if they were waiting for confirmation of the corresponding orders.

• Protection/pressure using the periods of the forecasts Some (rare) companies use the difference between the firm period received from their customers and the one they send to their suppliers as a way to protect their smallest partners, who may hardly deal with large variation of the demand.

• Load smoothing at supplier's Load smoothing may be an important issue for SMEs, which have a limited capacity. During the periods of high load, some orders are often delayed while when the load is lower, SMEs are looking for work in order to get minimum incomes.

• Protection against variations of load As seen in previous point, load smoothing can be performed on the supplier's side but also by the customer: in some cases, this problem was formally taken into account by the customers willing to protect their smallest suppliers.

• Link between price and cycle time Satisfying urgent orders is part of the daily work in aeronautical supply chains; it usually means spending extra money (due to extra hours, etc.) or postponing other orders considered as less urgent, with the result of perturbations in the planning. In some very specific cases, we have seen that the principle of a priority negotiation of the price and cycle time could be considered in order to address the problem of these urgencies.

• Information sharing

As already stated, many SMEs are facing a variable demand that they can hardly satisfy at low cost. Even if some orders are not as urgent as others, this information is not often shared by the customer. As a consequence, the SMEs have to make their decisions (on the priority of orders, grouping of similar orders, adjustment of lot sizes, etc.) on the sole base of internal considerations. Some cases of customers sharing such type of information with their suppliers have nevertheless been noticed.

• Lot sizes

Lot size is an important item, negotiated in the contracts. Nevertheless, SMEs have to decrease their costs through time, and have so to find solutions for constantly increasing the efficiency of their production system. In order to do this, most of them may need to provisionally increase their lot sizes. Therefore, many suppliers try to group various orders from their customers in order to decrease their set-ups.

Looking back at the studies, important problems have been described in purchasing of raw material/component and on the delivery of the requirements. Therefore, we have especially focused on the aspects of the supply and demand process, such as period of forecasts, load variations, order priorities, lot sizes, or purchasing cycle times, which were the objects of many hidden practices, especially from the suppliers. Usually, "supplier development" is considered as a longterm approach to deal with these problems, many customers considering that they are the proof of a lack of maturity of their suppliers. In that purpose, many projects have been launched during the last five years aiming for instance at disseminating the principles of MRP and lean management in the SMEs of the aeronautic sector.

For us, practices are linked to actual needs, closely attached to a type of relationship between supplier and customer, even if their result can be considered as negative. Therefore, we suggest to have a different attitude, and to consider that the practices of the suppliers, even if they may be unacceptable by their customers, are the symptoms of real problems. Therefore, we propose to turn these "hidden" practices into public ones, subject to negotiation with the partner. In order to illustrate this, we have focused on four points, detailed in next section.

CONTEXT AND MODELS FOR SUPPLY CHAIN NEGOTIATION

Our goal here is not to suggest a so-called "optimal" negotiation process, but to take some real empirical situations from case studies as examples, and try to include them into a consistent formal negotiation process, using Business Process Diagram [START_REF] Bpmn | Documents Associated with Business Process Model and Notation (BPMN) Version 2[END_REF], in order to check their real potential. Therefore, the cases mentioned are not for us a closed list, but an illustration of what can be brought by extending the objects of the negotiation process, which may concern quite different aspects. In the proposed negotiation processes, we shall first consider four items based on the case studies: periods of forecasts, load variation, price and cycle time, then order priority and lot sizes.

Period of forecast

In the aeronautical industry, the forecast usually consists of firm, flexible and free periods. As seen from the case studies, the problems are basically due to possible inconsistencies between the firm period and the cycle time of the orders, or the link between the lengths of the periods received by the customer and those he sends to his supplier.

Normally, after building a S&OP (Sales and Operations Plan) and a MPS (Master Production Schedule) (points ! and "), the supply plan, one of the outputs of MRP, is generated according to the contractual lengths of firm, flexible and free periods (point #).

The supply plan is considered as forecasts by the supplier (point $). The supplier makes then his own MRP calculation (point %), allowing him to build his own supply plan (not mentioned in Fig. 2) and his load plan (point &). Having taken into account his cycle time and the one of his suppliers, the supplier is able to check whether this load plan is consistent or not, or in other terms whether he takes too much risks (for instance by ordering parts on the base of the flexible period of forecasts, point '). Depending on additional information on his customers and suppliers (such as "can they be urged or not? Do they have financial stability or not?"), he decides whether these risks are acceptable or not (point (). If he considers that he takes more risks than his partners (customers and suppliers), he may ask for negotiation (point )). Of course, the notion of "acceptable risk", should be defined with better accuracy, which has not been done here since it is hard to formalize whereas decision maker have usually a clear view on what is "acceptable" or not.

The customer performs the same evaluation: he makes his assessment of both internal risks and risks he assumes to be on supplier's side (point *). This assessment of course considers the received horizon of the firm period from his own customer, the horizon of the firm period he sends to his supplier, his internal cycle time and his supplier's cycle time. It should also include his opinion on the cycle time from supplier's suppliers, the real costs of his suppliers, etc. This information is usually only assessed, since it is seldom provided by the supplier. The risk taken by the customer somehow proportional to the difference between the horizon he receives and the horizon he sends. It can be different for each of his suppliers, since two different suppliers do not need the same protection, or in other terms do not deserve that the customer takes the same risk (it is for instance acceptable to take risks for protecting a critical supplier, but not a "common" one). Such assessment will provide a customer's vision on the allocation of risks between him and his suppliers. The next step is to balance the customer's own strength and its supplier's strength and weakness, aiming at assessing the acceptability of the risks he takes (point +). For instance, the customer may consider that he should take lower risks if his supplier has more "strength" than him. Of course, this assessment is very subjective, but is indeed done daily in real situations, within less formalized processes. If, from customer's vision, risks are not acceptable, he will request a negotiation process (point ,). Otherwise, the customer will accept the current plans (point -).

Therefore, three triggers may launch negotiation: request from customer, request from supplier, and request from both customer and supplier. Surely, the visions of risks allocation and acceptability may be opposed at the customer and supplier side, mainly because a company knows his own problems much better than his partners' and may so overestimate them. In any case, sharing real information instead of trying to assess the situation of one's partner could facilitate to reach a consensus, but would certainly lead to other problems linked for instance to confidentiality. After the negotiation process, a new agreed horizon will be integrated into the customer's MRP plan.

Load Variation

In case of load variation, instead of considering that the supplier has to, or cannot answer to an overload if it is consistent with the contract, overloads (or lacks of loads) could also be negotiated.

On the customer's side, the negotiation on load variation is proposed after the MRP step has been performed (see the top part of Figure 3). After S&OP and MPS design, the customer begins the MRP calculation (point !). The customer may then consider the supply plan for each of his suppliers in order to identify high load variations (by comparing the load for current and previous periods) (point "). For dealing with high load variation, the flexibility of the mid-term capacity of the supplier is essential. Therefore, the customer has to estimate the mid-term capacity on the supplier's side (point #), as well as the costs to manage such capacity (point $). As a consequence, additional information on the supplier's capacity, including internal regular and overtime capacity, external accessible capacity (subcontracting capacity) (point %), and additional information of related costs (point &) are important inputs for this estimation. Depending on the closeness of the relationship, this information can be known or estimated.

Based on the results, the customer needs to assess the feasibility of the load variation expected in the current period (point '). From the customer's vision, if the supplier is capable to manage this load variation, the current plan is considered as feasible and the MRP result is accepted (point (). Otherwise, the customer requests a negotiation process, considering as doubtful the supplier's capability to perform satisfied delivery when facing the considered load variation (point )).

On the supplier's side, the detection of the problem of capacity is not based on estimation, but on the actual capacity/load situation. According to the result of the load planning (point *), the supplier identifies a possible capacity problem (point +) and checks the feasibility (point ,) to address this problem (for instance, by extra hours or subcontracting in case of increase, by other solutions aiming at decreasing his capacity in case of decrease). Therefore, two important factors have to be taken into account: i) price paid by customer (point -) and ii) cost for extra capacity or decrease of capacity (point .).

From the supplier's vision, if the capacity change is considered as feasible, the current plans are accepted (point /). Otherwise, the supplier will request a negotiation process and communicate his capacity problems to the customer (point 0).

Again, the negotiation process will be triggered either by a customer request, a supplier request or a double request (not considered here). Of course, if the problem is detected by one of the partners, the other has to agree on the fact that there is an actual problem. For instance, a customer may detect a high overload, which may have no consequence for a supplier, if other customers of this supplier have decreased their own orders during the same period.

Price and Cycle Time

Urgencies are detected at the customer's side but they also have consequences for the supplier, challenged through his flexibility and adjustment of capacity. Therefore, we suggest to negotiate price and cycle time of urgent orders as the third item of our model.

The negotiation on price and cycle time is considered here for a small number of urgent orders, see Figure 4. At the customer's side, MRP calculation is based on S&OP and MPS, also taking into account the urgent orders sent by customer's customer (point ! of Figure 4), at a level consistent with their degree of anticipation.

The results of the MRP step will provide a clear view on the material requirements induced by these urgent orders to the supplier (point "): they may have no effects on the current supply plan, or urgent material orders may be necessary. After load planning, the required due dates of the materials are confirmed (point #), then the customer needs to estimate the feasibility of urgent orders on supplier's side (point $), as well as the possible extra cost for the supplier (point %). According to customer's vision, if the urgent orders are considered as feasible, meaning that the supplier is supposed to be capable to deal with such urgency, the current plan is accepted (point &) and the urgent orders are sent to the supplier (point '). Otherwise, if the customer thinks that his supplier is not able to deal with these urgent orders (based on customer's estimation), negotiation is requested (point ().

At the supplier's side, the urgent orders usually arrive at the load planning or detailed scheduling levels (point )). Based on the allocation of capacity/load towards each customer, the supplier needs to check whether it is feasible to deliver the urgent order(s) (point *) in the conditions required by the customer (including price) (point +). If the actual situation allows the supplier to adjust his capacity/load for fulfilling the urgent orders, the current plan is acceptable and the production process is launched (point ,). Otherwise, the supplier sends a request for negotiation (point -), and notifies his customer that delivery as requested is questionable in the present situation. Therefore, three possible triggers launch the negotiation on price and cycle time of urgent orders: customer request, supplier request and double request from both customer and supplier. After negotiation on the urgent orders, the new agreed due date will be integrated in both customer and supplier's plans (point ., /).

Order priority and lot size

The final item we suggest to put into the negotiation process is the orders priority and lot sizes. From the interviews, we have seen real cases where SMEs are trying to regroup orders having common features, usually in order to decrease the set-up times. On the other hand, if they do not have additional information to the due dates, it is common that the suppliers use an internal priority for scheduling the orders at the operational level if all the orders cannot be fulfilled in time, as well as when urgent orders are required. As a consequence, tardy orders towards one or several customers may occur. Temporal margins or safety stocks may allow the customer to face delayed delivery on some of the orders, but this information is not always shared with the suppliers.

The negotiation on orders priority and lot sizes occurs at the operational levels is mainly related to constraints on capacity or cost (see Figure 5). At the customer's side, depending on the lot sizing policy, the lot size is either an input (for instance, if an economical lot size has been defined) (point !) or a result (if a lot-for-lot policy is used) (point "). The customer may in the last case need to check whether the supplier's constraints on lot sizes are consistent with his actual requirements (point #). If, from the customer's point of view, no problem is expected, the current MRP calculation is acceptable and a load plan and detailed schedule can be performed (points $, %). If the customer considers that the current lot size is not feasible, due to the constraints of the supplier, a request for negotiation on lot size will be sent (point &).

At the supplier's side, there are two major tasks: one is to check the feasibility on lot sizes based on the results of the MRP calculation (point '); the other is to check the respect of the due dates based on the load planning and detailed scheduling (point ().

In order to reduce the frequency of the set-ups, the suppliers usually regroup orders of similar parts coming from a single, or eventually from several, customers. As a consequence, the real production lot size may be larger than the contractual one with one customer, which may be necessary to meet acceptable prices. As seen during the interviews, these internal adjustments might occasionally result in early or delayed deliveries. Therefore, if the supplier considers that increasing the current contractual lot size could possibly lead to some benefits (point )), a request for negotiation on lot sizes can be sent to the customer (point *).

Similarly, if it is not possible to meet all the due dates of the orders in process, instead of defining internal priorities linked to the importance of each customer (point +), the supplier can ask for a negotiation on the real priorities of the orders (point *), which would allow him to define a schedule possibly acceptable by all the customers.

The negotiation process on lot sizes is launched by the customer's request, supplier's request or both, while problems on orders priorities are detected by the supplier. The corresponding negotiation process may so only be launched upon supplier's request.

Figure 5. Business Process Diagram for order priorities and lot sizes negotiations After the negotiation process, the new agreed lot sizes will be integrated into the MRP calculation of both customer and supplier (points ,, -), and the order priorities an input for the load planning and scheduling (points ., /). It can be noticed that these two negotiations are quite different from the previous ones, since they may involve several customers at the same time, and would so be certainly more difficult to handle in practice.

So far, we have introduced the suggested context of negotiation, which results are obviously linked to extra costs related with inventory, purchasing, capacity, etc. and the ways to compensate them. Back to the case studies, some practices provide us the primary idea of compensable extra payment. In that purpose, it is necessary to define a cost model which bases are summarized in next section.

ASSESSMENT OF THE MODELS FOR NEGOTIATION

Extra cost assessment

We have summarized the different costs present in the supply and demand process in Figure 5. We consider without loss of generalization that the buyer (customer) pays for the transportation of the goods (considering other solutions do not set into question the consistence of the framework). So, a supply chain member buys components/materials from his suppliers, pays the material cost and transportation cost and stores the components into material (components) inventories before releasing production orders. As a consequence, purchasing costs include here the costs of the materials, of the transportation and of the inventories of raw materials/components (see Figure 5). If the supplier's delivery is delayed, a penalty cost may be charged on this supplier, which decreases the purchasing cost of the customer.

Considering the items that have to be negotiated (see section 4), it is important to include issues related to lot sizes and resource capacity in the cost model. Therefore, we have decided to describe the internal production costs then include the cost linked to the capacity of the used work center (using regular or extra-hours) or linked to sub-contracting, as well as set-up costs and finished product inventory carrying costs (see Figure 5). Penalty costs for delayed delivery (shortage) towards the customer may also be included, due by the manufacturer.

Each supply chain member, either supplier or customer, has the same total cost structure: purchasing costs and production costs, plus benefit, is equal to the sales revenue.

Figure 5. Suggested structure of total cost Using this structure of total cost, we can identify for each negotiable item the related elemental costs, which define the conditions of negotiation.

A negotiation on the period of forecast on customer's side is usually triggered by a request for an increased firm period sent by his supplier. In that case, the customer takes the risk to store parts delivered by the supplier, being unsure to really need them. As a consequence, there is a corresponding extra carrying cost, depending on the confirmation of his own customer's demand. On supplier's side, a request from the customer asking to decrease the firm period is usually received, with as a possible result, the necessity to order raw materials on the base of the flexible period of the forecasts, resulting in increased carrying costs if the expected demand is not confirmed. The related elementary costs are listed in Table 1.

Extra Cost Related elementary costs Inventory cost Inventory carrying cost

Penalty cost Purchasing cost Table 1. Elements for cost calculation in period of forecast negotiation

During the negotiation of the load variation, the variables taken into account for extra cost assessment are different for the customer and the supplier, since load variation leads to problems of capacity at supplier's side whereas they are linked with inventory levels at customer's side. We have summarized the related costs in Table 2, distinguishing the customer side from supplier side.

In the negotiation of order priority and lot size, at the supplier's side, a so-called "optimal" manufacturing lot size is still often defined, depending on the set-up costs and inventory carrying cost (see for instance Wilson's formula [START_REF] Camisullis | A new need for safety stocks in a supply chain dedicated to customized mass production[END_REF]). At the customer's side, the purchasing lot size of the components depends on the delivery cost and inventory carrying cost. Indeed, deliveries in large quantities may be less expensive, but this is seldom the case in the aeronautic industry, quantities being relatively low and unitary prices, and consequently carrying costs, high.

The elements allowing to calculate extra costs are listed in Table 4, showing considerations in lot sizes extra cost assessment, transport cost, back order cost and purchasing/sale price.

The listed costs allow us to have a global view of the extra costs due to the suggested negotiation items. It is obvious that if customer and supplier reach a mutual agreement on the balance of these extra costs and the extra payment of compensation, the suggested negotiation processes become realistic. Therefore, the assessment of the extra costs, allowing cost/benefit and risk sharing between partners, is also considered as one of the main requirements for making this negotiation possible.

Another constraint of our proposals is that such negotiations directly require the emphasis of collaborative relationships, mainly related with trust, maturity, power, dependency and goodwill, which are important factors for negotiation [START_REF] Ming | A taxonomy of the situations of cooperation in supply chains[END_REF]. We will focus on these in the next section.

Collaborative relationship assessment

The suggested negotiation processes aim at helping to increase the performance of relationship by turning hidden problems into negotiation items, which may lead to a better supply chain collaboration. Nevertheless, it is clear that making these processes realistic requires an intensive exchange of information, including data usually considered as confidential, like internal lead time, capacity or costs. Opportunistic behaviors, exaggerated con-straints publishing, false information sharing, etc. are inevitably barriers towards our proposal. We try in next section to go give some basic ideas on the collaborative relationships that are in our opinion consistent with the negotiation framework we have suggested.

Customer's side

In the customer's point of view, if the customer distrusts or feels indifference towards his supplier, a strict execution of the contract is certainly the common way to perform cooperation in the supply chain. In our proposals, except for price, cycle time and lot sizes, the other suggested items are usually fixed in contract. However, negotiation on these items needs a high level of trust. Even for urgent orders management, a complex issue which is often outside the terms of the contract, good performance of negotiation on price and cycle time requires a long-term and better managed relationship, in which trust is a prerequisite. Thereby, we think that these negotiations all require a trustful collaborative relationship.

As mentioned, the four suggested negotiation items are based on hidden constraints seen in real practices. However, it is clear that dominated members have insufficient power to publish their constraints towards their customer. Thereby, when the customers have a high over the suppliers, the customer should be ready to launch the negotiation process as soon as he expects problems at his supplier's, in order to avoid hidden problems.

Supplier's side

If the supplier distrusts or feels indifference towards his customer, the contract will be the base of the cooperation, whereas a strict execution of the contract is in our opinion a barrier against a better collaboration and negotiation on the occurring problems. Therefore, we also limit our suggested negotiation processes to the collaborative relationships with high level of trust.

Negotiation launched by the supplier is always aiming at publishing operational problems. As a consequence, when the changes/conflicts on the supplier's side have critical impacts on the customer, in another term when the customer is dependent towards the supplier, we also suggest that the supplier should launch the negotiation process aiming at publishing real problems and then minimizing the following impacts through sharing risks/costs.

As a brief synthesis, trustful collaborative relationships are the primary conditions for our suggested negotiation process. Depending on the allocation of power and dependency, customers are suggested to launch the negotiations in order to avoid potential problems, while suppliers are encouraged to publish their real constraints.

CONCLUSION

The basic ideas contained in our proposal come from cases studies in the aeronautic industry. On the base of a comparison between expected behaviors and real ones in real supply chains, we have suggested to include unexpected practices, expressing in our opinion real problems, in negotiation processes. The context of these negotiation processes has been defined in details on four subjects: periods of forecast, load variation, price and cycle time, and order priority and lot sizes. These items are not a closed list of what can be negotiable but aim at providing examples of the fact that, paradoxically, taking into account the partner's constraints may in some cases finally lead to a win-win situation.

We have briefly presented the basic guidelines of a cost structure, which would be the basis of the negotiations. This cost structure is developed in [START_REF] Ming | Models for customer-supplier negotiation in a collaborative supply chain[END_REF] and examples of negotiation based on it are provided. The conclusions of the first tests are that, as expected, a winwin situation may be the result of negotiation in some cases, under conditions which analysis is in progress. In order to automate the negotiation process in a realistic way, our perspectives are now to model the negotiation itself by game theory, more and more often considered for modeling customer/supplier relations in Supply Chains.

Figure 2 .

 2 Figure 2. Business Process Diagram of period of forecast negotiation

Figure 3 .

 3 Figure 3. Business Process Diagram for load variation negotiation

Figure 4 .

 4 Figure 4. Business Process Diagram for price and cycle time negotiation

 4. Elements for cost calculation in order priorities and lot sizes negotiation Concerning urgent orders negotiation, at the supplier's side, the extra costs are mainly concerning the possible increase of capacity required by the processing of the urgent orders, and eventually a cost for re-planning. At the customer's side, the changes on the required delivery time depend on the slack time kept by the customer. There are two possibilities for assessing extra costs: i) the due date is mandatory, and an agreement has to be found on the price, ii) the due date can be negotiated, resulting in a lower increase of the price. Detailed costs are listed in Table 3.


Bertin Aurélie
email: aurelie.bertin@saftbatteries.com

* Noyes

Daniel * Clermont

Problem solving methods as Lessons Learned System instrumentation into a PLM tool

Keywords: Experience feedback, Lessons Learned System, problem solving method, product lifecycle management, continuous improvement

Among the continuous improvement tools of the performance in enterprise, the experience feedback represents undoubtedly an effective lever of progress by offering important prospects for a progression in almost all the industrial sectors. However, several reserves to its use slow down the diffusion of its employment. We are interested in the installation of experience feedback system in a partner enterprise. In this paper, we propose an instrumentation of a Lessons Learned System (LLS) by problem solving methods (PSM) and its integration with a product lifecycle management (PLM). These proposals support an improvement of LLS performance and a facility of his application.

INTRODUCTION

Application of continuous improvement principles in companies leads to the use of a set of methods and tools in order to maximize levels of productivity efficiency, product quality and cost reduction.

Problem solving methods that are basic mechanisms of the quality approaches constitute an important part of this set. They underline a high potential of possible improvement if companies succeed in being exempt from the weight of attendant formalism and requirements.

In addition, the consideration of Lessons Learned System (LLS) at several levels of business activity constitutes one of the surest means of increasing the product quality and efficiency. A lot of companies have adopted the LLS in their continuous improvement plan because they are concerned about prioritizing or preserving their immaterial capital.

Finally, still in this logic of continuous improvement, many businesses have chosen to deploy Product Lifecycle Management (PLM) solutions. The aim is to improve the management of the entirety data related to the product, the collaboration among several departments, the definition of the working organization, the formalization of exchanges in order to strengthen the decision making.

In partnership with Saft, leader in the design of high-tech batteries, our work focus is situated within this context, outlined as a "multi-approach" continuous improvement.

The overall objective of our work is to facilitate a LLS through problem-solving methods (PSM) integrated into a PLM system. Several objectives underlie the study.

First, the coupling LLS-PLM will facilitate the implementation of the LLS due to the dynamism caused (or forced) by the establishment of PLM system in the company. Indeed, even if the interest in the LLS is apparent, it's often laborious to integrate the LLS into businesses.

Secondly, PSM-LLS coupling should allow the exploitation of analysis mechanisms and of reasoning involved in PSM. It strengthens the stages of LLS, notably during the activities of experiences acquisition and formalization.

Lastly, the support of the study is a practical framework of a continuous improvement project in Saft Company. This framework does not alter the generic nature of the approach because it can be reproduced in the shown form in most of the companies.

The paper is organized into four sections.

-Section 2 introduces key concepts of problem solving methods such as the generic framework and the defined Saft PSM methodology which allows to lead several methods.

-Section 3 is devoted to the first steps in achieving these methods and their connection to the LLS. Stress is put on the description of situations making up the experiments.

-Section 4 is dedicated to mechanisms implicated in the process of the PLM.

-Conclusion and perspectives are presented in Section 5.

PROBLEM SOLVING METHODS

Generic Framework

Problem solving is a continuous improvement process ensuring the processing and the resolution of negative events. This process carries out many well-known dedicated methods and tools in literature. As an example we can quote PDCA [Deming, 1986], fault tree [START_REF] Mortureux | Appro instrumentale de constructi documents structurés[END_REF], 5 why, PSDM, 8D… Each method is made up from of a succes ensuring a progressive processing from description to the explicitation of the implem recognized efficient. The stages are of v according to the accuracy of processing and abstraction engaged by the method. complexity level of these stages varies method strength (investigation spectrum, engaged means, processing duration…). Ho generate a generic framework.

We identify four generic steps always problem solving method. They can be found or by discretization of the ones constituting They are:

-(I) the problem definition, consisting location, collection and description. It step that allows firstly the identification o and the characterization of the problem then, the analysis of the problem, to recurrence and the appreciation of complexity The choice of appropriate p method to use, and the application implemented solution (sizing of curre assessment of return of investment) depen -(II) the root causes research, aimed at identification leading to the negative devi consists in identifying relevant inform guiding toward the root cause(s). It variables levels of complexity according t the disciplinary synergy required identifying the root causes often follow approach.

-(III) the solutions design, aiming for and categorization, according to exploita curative actions (returning the item to performance) and sometimes of corr (elimination of the root cause) to rectify/r at the best situation. This stage focuses o objective, the ease of solutions adapta reduction and the expected benefits.

-(IV) the action deployment, consisting choice between potential solutions and necessary activities to implement the ch Furthermore, several methods propose sp capitalize the acquired experience.

The problem solving constitutes experience is clarified as the approach proceeds. The c created or collected information during the allow the record of all the necessary data used experience, to finally lie a memory storing experiences.

Defined methodology

One of the first choices made regarding the problem solving method is the methodol implicit for a team working systematically method, but it comes often under an adaptatio of a succession of stages ssing from the problem f the implemented solutions are of variables values cessing and to the level of Furthermore, the depending on the spectrum, importance of ation…). However we can always included in any an be found by aggregation onstituting the method itself. consisting of the event cription. It is a paramount entification of relevant data the problem in its context, , to the study of the eciation of the problem ppropriate problem solving application scale of the ng of current losses and depends on this step.

ed at the key elements negative deviation. This step evant information and in cause(s). It invokes very y according to the needs and required. Furthermore, often follows an iterative for the establishment g to exploitable criteria, of a nominal level of corrective actions rectify/restore the work focuses on the resolution adaptation, the risks consisting in performing a olutions and planning the ement the chosen solutions.

propose specific actions to experience. The experience . The capitalization of the resolution will used to process this of formalized past regarding the results of the methodology taken. Its ally with the same an adaptation of the solving methodology's "strength" to im complexity related to the problem.

One of the major issues with methodologies is the evaluation o which is only fully perceived dur sometimes necessary to switch method during the process. Despit and tools dedicated to the problem doesn't propose any methodology, complexity, to switch during the resolution method to another more Classically, possible scenarios are method during the resolution proc all the processing from a method to the revealed complexity (figure substitute during the process the those of another suitable method (f Fig. 1. PSM methods hanging.

In our working context (in Saft implemented a generic problems methodology is based on Saft's b another approach combining the pr Established on a common basis stage of the PSM framework ( methodology lets a choice betwee to process the second, third and the complexity level felt: eleme (figure 2).

Fig. 2. Saft's methodology of PMS

We specify in a BPMN (Bu Notation) diagram in figure 3, the methodology. Saft tackles a PSM where the grouping stage doesn generic framework stages. Thi "Problem definition" stage (I) into gateway. According to the compl the more or less complex fulfillm phases. These phases represent th PSM framework, where the "Sol "Action deployment" (IV) are mer The basis of our LLS construc because it will be done both on th the method and on its potential out " to implement relating to the the problem.

with the choice of resolution evaluation of the problem complexity erceived during its resolution. So, it is switch to another most appropriate Despite the multitude of methods problems resolution, the literature ethodology, based on several levels of h during the processing from a simple another more complex or vice versa. scenarios are: i) to change the decided solution process, with the resumption of m a method to another more appropriate lexity (figure 1: cases a, b,..., c), ii) to

the not yet carried out stages by ble method (figure 1: cases d, e…).

text (in Saft) we have developed and problems solving methodology. This d on Saft's best practices and it allows bining the previous ones. mon basis related to the first generic framework (cf. paragraph 2.1), Saft's hoice between three completion modes and fourth stages, depending on l felt: elementary, simple or complex logy of PMS.

BPMN (Business Process Modeling

the constitutive elements of the ckles a PSM beginning methodology stage doesn't correspond to the PSM This methodology cuts the into two activities leading to a to the complexity, the decision leads to plex fulfillment or not of two major represent the remaining stages of the ere the "Solution design" (III) and the (IV) are merged as the last phase. construction is the capitalization ne both on the stages performed during potential outcomes. At every stage of the methodology tools ensures to obtain sufficient the next step. It provides factual efforts of investigation and the to the current case.

LESSONS LEARNED SYS

Generalities

LLS is a process involving strate identify, create, represent, distrib adoption of experiences [Meiling, Among several proposed definitio we consider the one of Rakoto [R LLS as "a structured approach information coming from positi treatment. It carries out a set of hu having to be managed in order errors repetition and favour some e

The LLS is composed of three mai knowledge from the generalization experiences i.e., the response made event. (figure 4). strategies and practices used to esent, distribute and make possible the es [START_REF] Meiling | Continuous im feedback in off-site construct University of Technology[END_REF]. sed definitions about LLS description, f Rakoto [START_REF] Rakoto | Integration of support in industrial proce Conference on Systems[END_REF] describing the d approach to capitalize and exploit from positive and/or negative event ut a set of human and material resources ed in order to contribute to minimize some efficient best practices".

Method & tool

of three main phases intended to build eneralization of one or several esponse made to the occurrence of an These three phases correspond to the action of:

-capitalization: location, collection and storage of relevant information related to the description of an event, the process mode and the obtained results. So, each treated event constitutes an experience, -processing: knowledge creation based on the analysis of the recorded information, -exploitation: use of knowledge and experiences to improve decision making during current process.

Of course, in our work, experiences are the problem solving as it has been described in paragraph 2.2.

Let us remind that a LLS is positive when it is committed to the identification and the enhancement of good practices. It is negative when used to resolve notable errors. Likewise, its scope is global when applied on the source process or local when the capitalized information is used by other processes.

Even if the LLS principles are easy to understand and its interest of use seems undeniable, its acceptance in enterprise is often restricted to difficulties. Some implementation features are often sources of conflict. According to the literature, the main implementation difficulties of LLS are:

-sociological and managerial, relating to the approach's impact on the actors: understanding of the approach, acceptance by the actors, adaptation to the new working methods ... [Parfouru, 2008],

-technical, relating to pitfalls often linked to the modes used for knowledge formalization (consolidation, structuring, interpretation…) and exploitation (access rights, modification…) [Dechy et al., 2008].

Finally, the LLS is an approach based on experiences capitalization, processing and usage of key information. These experiences can come from past experience or from current business processes. This approach ensures companies to improve their informational property: they can build knowledge on their own specificities about past business activities.

Despite the difficulties encountered during the implementation of such methods, the LLS has a strong added value to improve decision-making and continuous improvement of working methods.

Saft used LLS since a long time and was confronted to several difficulties. A specific study [Bertin et al, 2010] revealed the limitation of the tools and approaches dedicated on Knowledge Management (KM). This audit allowed us to establish Saft's needs i.e. a new solution of LLS compatible with its skills and working behavior.

Use of a PLM software

As part of improving performance, Saft Corporate initiated a PLM software implementation program (choice of Windchill ® PDMLink). Our idea is to exploit the PLM functionalities and the strong sociological change framework to implement an efficient LLS.

PLM is a global software aimed at creating a collaborative environment including all the actors involved into the development cycle of a product. The PLM allows organizing and systematizing common and formal realization processes (called workflow) where the actors responsibilities, rights, roles are defined as input and output data of theses workflows.

Information logged in the common database of the PLM is defined as the repository which implements a structuration of data based on the use of metadata. The data provide information on individuals (objects), classes (all types of objects), attributes (properties of the object), relations (links between objects) and events [START_REF] Chebel Morello | Enje d'expérience[END_REF]. This set of varied information is structured in a meta referential.

Applications experts, such as PLM software, correspond to different business needs of actors in the product life cycle. Their main target is to help to technical decision making. Indeed, these applications integrate all informational and technical data about the product during its life cycle [Pol G, et al 2008]. Through the management of these elements, product configuration and documentation, these applications provide a traceability of design process, and product data, and a partial traceability and monitoring of the decisions taken. At each step of life cycle, these applications can help the decision makers with the consistency of the information heritage of the product [Saaksvuori, 2004].

The PLM contains all of the informational references about the product, i.e. business data directly resulting from the experiences induced by the process life cycle. Through its mechanism, PLM is suitable to the integration of a LLS. It allows to automatically supporting many activities relating to capitalization, processing and exploitation. These intrinsic features of the PLM provide a non-intrusive LLS to the user because of its usage in the technical working software.

Thus, PLM tools allow to collect and to structure the generated information during developments, while orchestrating the making-up activities of this process.

It's interesting to use the already existing PLM tool to implement our solution. This is a strategic decision since the technical environment is already formalized and mastered and its actors are confident.

Relationship with the problems solving methods

Our goal is to deploy a LLS, on one hand, instrumented through a methodology of problem solving and, on other hand, included into the PLM system of the enterprise with the final goal to deal with the events inducing negative drift.

In the four problem solving key stages presented in § 2.1, we have identified the three phases of capitalization, processing and exploitation of knowledge and experiences of the LLS.

The phase of experience capitalization is easily identifiable at each PSM stage. It's in the one hand in the definition problem (I) like the description step of the event and on the other hand in the registration of the entire fieldwork's information collected and recorded in the tools. Thus, capitalization goes beyond the simple registration of the result by considering all the significant information that describes treatment:

-the complexity and criticality of the event -the selected resolution process, -the identification of involved resources, -the root causes and their justification (meas -the solutions designed and the ones selecte -the actions of implementation and the plan -the recorded results and deviations from ob -the tools and the controls carried out o validate the solution.

Important added value of the LLS is th knowledge; therefore capitalization must be o sense, regarding both the results as the proc involved to establish the results as the results t

The LLS processing phase concerns the acq experts of the significant elements capi previous resolutions to generate standards business processes. These treatments involve of experts able to generalize an experience knowledge… while ensuring overall com treatment can lead to: i) the creation of new k update, ii) the creation or modification of (updated technical documents after an expert concerned field).

The LLS exploitation phase will allow the ac use the experiences and the knowledge processing phase by recovering the busin standards in a new development.

The actor will also be able to exploit this resolve the new problem. The method allow capitalized information in the previous proces similarity of a new problem. We can make thi to the case based reasoning approach.

Another important added value of our prop addition, by use of a PLM tool, of an autom this generic methodology.

The objective is to operate the standard featu to operationalize the defined methodology an the referential of the enterprise, continuous im the technical data related to the product life

INSTRUMENTATION HELD BY A

Changes management

The "Change management" is a standard wor by the editors of PLM process that, in the case based on the CMII © standard (Change Manag [CMII, 2010]. The management of the standardized closed-loop process used to information. It involves a series of activities to manage and control all of the changes i evolution toward a desired configuration. management process consists of four interdep processes that characterize each phase o management (cf. figure 5):

describes the problem event, resources, ication (measures), selected, and the planning, tions from objectives, ed out on the result to LLS is the creation of on must be organized in this s as the process and means s the results themselves.

erns the acquisition by the ements capitalized during te standards or rules for ents involve the intervention n experience in a specific overall compliance. This ion of new knowledge or its ification of technical data ter an expert reflection on a allow the actors to directly knowledge created in the g the business rules and exploit this information to ethod allows access to the vious processes to study the can make this process closer of our proposal lies in the of an automated support to tandard features of the PLM thodology and to manage in continuous improvement on roduct life-cycle. Each of these four processes ma PLM data characterized by attribu with a dedicated life cycle. The c by a combination of four chan controlled information is processe system of management that ensure and audit activities are conducted The business process infrastructur and characterized by key attribu come from:

-the PLM in an automatic information concerning objec management or the informa description transmitted from o -selection among drop-down context information -manual entry in the case of th comments, -link to an external item to the P The contributions of the PLM use management approach is presente 2010].

Overview of the methodology

The change management proc collaborative core business proc integrates all of the data affect targeting data and process support <PR/CR/CN/CT> of the managing problem-solving stages.

The similarities of construction and changes and problem resolution p level of the formalism of the app the main activities. While the chan a series of development's data t process is based on a series o activities to obtain relevant inform R): description of the event by the actor (CR): description of the event and ions by the business expert(s), deployment plan of the solutions ess experts, statement of work for implementation the object.

rocesses manages a type of identified ed by attributes, involved in a workflow

The change process is managed f four change objects. All formally n is processed through the standardized nt that ensures proper validation, release e conducted [CMII, 2010].

anagement process infrastructure elements are established key attributes whose completion can n automatic way as, for example, erning objects related to the changes information of the modification itted from one stage to another, down lists for description or he case of the additional information or item to the PLM referential.

PLM use to "automate" knowledge h is presented in PLM10 [Bertin & al, odology implemented in the PLM ement process is identified as a process [CMII, 2010] which data affected by a change of state: cess support. The four macro-processes the managing may be linked to the four nstruction and definition of management resolution process are identified at the m of the approach and the objective of hile the change management process is data tasks, the problem-solving a series of reflections and analysis information. Our proposal is to include the methodological and reflection a problem solving to the change manageme improve the latter. The basic requirements standard can be implemented as a m however to achieve the highest levels of efficiency software tool will eventually be ne 2010].

Experience feedback via LLS cards

The PLM allows us to capitalize information a according to a predefined formalism. H metadata enables only the structuring and the information. The contents which is the co is not managed by the metadata. The esta standard frame of statement allows the experiments using drop-down menus and elements, easily identifiable in the database.

Thus, we can establish LLS cards with th reported information. They include the sy contents from the experience. This statement i an automatic way directly from the tool for re information and in manual means for additiona

The LLS card processing is an integral part o process as it is initiated at the launch of the then set in automatic fields. Also its complet represents a set of tasks of the solutions deploy Registered in the PLM base, this card remains the objects affected by the change manageme elaborated memory of experiences.

CONCLUSION

The theoretical benefits of the combined app PSM, LLS and PLM concepts are undeniable.

The first results that we have achieved in the the platform in industrial context have confirm

In practice, the instantiation of the platform step approach: the modeling of the PL characterization of the experience feed knowledge management and the instrumentat process of change management to bring the reflection activities of the e management process to equirements defined in this d as a manual process, t levels of throughput and ntually be necessary [CMII,

This articulation PLM -LLSformalization of a generic problem by the Change Management Proce inherent activities of the prob integrating in the logic of Change represented in figure 6.

rticulation between PLM management process and the defined LL gement can integrate tools problem solving information and experiences rmalism. However, using and the containing of ich is the core of any LLS, he establishment of a lows the users to describe menus and terms or key e database.

with the help of the the synthesis of the is statement is carried out in for recoverable PLM additional information. art of the resolution launch of the approach and completion and update utions deployment plan. card remains to be linked to e management to enrich the ombined application of the undeniable. eved in the development of have confirmed this interest. he platform follows a three of the PLM field, the rience feedback through instrumentation of the PLM bring the LLS The last step is ongoing and will b operationalization of the platform.

Fig. 3

 3 Fig. 3. ProblEach step of the generic process is supported b management tools and working methods specific needs. Some usual tools can be us stages of our methodology.

ELD

  the case of our study is ange Management Institute) ent of the changes is a ess used to release new activities whose purpose is he changes involved in the onfiguration. The Change four interdependent macroch phase of the change -problem report (PR): descriptio which found the problem, -change request (CR): descr proposal of solutions by the -change notice (CN): deploym selected by business experts -change task (CT): statement of of the change on the object.

Fig. 5 .

 5 Fig. 5. Modification management p

Fig. 6 .

 6 Fig. 6. Articulation b Key stages of the change management can and/or methods included in the methodology.

Table 1 . Methodology instrument

 1

	Since Saft's confidentiality must be respect
	communicate about the tools used by our pr
	Fig. 4. Lessons learned system process