- Email: [email protected]
Organizational structures for distributed networks of enterprises
Copyright ® lFAC Manufacturing. Modeling. Management and Control. Patras. Greece. 2000
ORGANlZA TIONAL STRUCTURES FOR DISTRIBUTED NETWORKS OF ENTERPRISES
Agostino Villa
Dipartimento di Sistemi di Produzione ed Economia dell'Azienda Politecnico di Torino, c.so Duca degli Abruzzi, 24, 10129 - Torino (1taly) Phone: +39-11-564. 7233;fax: -564.7299; e-mail: [email protected]
Abstract: This paper analizes the emerging organizations in business and production denoted "Networks of ENterprises (NEN)", namely organizations generated by a temporary agreement of several firms which aim to cooperate together in a common business area. The aim of the paper is to show how an effective integration of the firms can be obtained through a NEN based on two structural basic elements: by connecting individual firms through "negotiation" interactions, and by managing connections through a "mediator". Both conditions are necessary to state and apply design criteria for a NEN, as well as to assure an efficient performance of the NEN operations. Copyright @2000 IFAC
Keywords: Enterprise, Integration, Organization, Networks
to process proper items and then operate on proper markets. Finally, the NEN agreement can also be used such as a transient situation during which all involved SMEs can verify their effective interest to become a partner in a consortium, for instance, or something else more structured. Owing to its interest, a NEN organization needs to be deeply analyzed and accurately modeled in order to develop methodological tools which could support its design and management. This is the main scope of this paper. The main concept on which all considerations will be based is that a NEN can be graphically represented such as a "graph of services and markets, alternatively connectetf': it means that each node "service" can be only connected with nodes "market" both upstream and downstream, as shown in Fig. 1 (according to an object-oriented representation, as in Rumbaugh et aI, 1991). In practice, this representation emphasizes that, in any network of enterprises, either related together or in competition, input and output flows of each enterprise are always directed from/to a market (Villa, 1999). Based on this idea, the paper will be organized into three Theses to be proved:
1. INTRODUCTION In recent years the globalization of business and production is pushing competitive enterprises to find new types of co-operation in order to maintain their competitiveness worldwide. Among the different types of agreements which can generate effective synergy of partners, a potential organization of enterprises can be originated on the basis of their complementarity. In this case, different enterprises, able to produce parts which can be utilized in similar final products, can give rise to a "virtual enterprise" in terms of a connecting network. More preciselyall enterprises which agree to be included into a NEN, sign an agreement of transparent cooperation in defining common industrial plans for specific products, but can maintain their independence and autonomy for any other production. This type of agreement presents some particular features of direct interest for several Small & Midscale Enterprises (SMEs). On one hand, the agreement can be temporary, because it only involves a part of the core business of any NEN member. On the other, it does not completely reduce the autonomy of each NEN member, since each one can still
77
1SI Thesis: Assumed a graphical representation of a global enterprise organized such as a NEN, then any operation among NEN components is performed in terms of "negotiation" among two or many enterprises having the same downstream market. 2nd Thesis: Assumed a formal model of the "negotiation" with presence of a "mediator" such to generate a non-conflicting allocation of resources/tasks, then each negotiation aims to produce an equilibrium situation among enterprises characterized by balanced production loads. 3rd Thesis: In an equilibrium situation as stated above, the graphical model of a NEN based on negotiation allows to define topological conditions, concerning interactions among enterprises, which states NEN design criteria.
pans connected together and modelled by a network of "objects". In such a network a node can either represent a "producer" (that means an enterprise supplying either components or end items) or a "market" (i.e. a service devoted to manage exchange of items among producers together, and from producers to end users). Note that each time a market drives items to end users, then it operates such as a "sink"; differently a market can only manage transactions among producers. Each node of given type (i.e. producer or market) can receive inputs only from a node of the different type, and the same happens for outputs. Then, a node producer can only receive inputs from nodes market, from which it obtains materials and components to be processed. Any node market can only receive inputs from nodes producers, which send their own end items to the market in order to sell them either to other nodes producers or to end users (final clients). A graphical representation of the concepts above stated is illustrated in Fig. 1.
2. GRAPIllCAL MODEL OF A NEN. Referring to the 1sI Thesis, as stated in (Villa, 1998, and 1999), a NEN can always be represented such as a graph, i.e. through the composition of physical orders
purchase
Demands VsA
Delivery fromB
Fig. 1. Example of simple NEN representation according to graphical modeling ideas. Depending on the two types of nodes, in principle two types of operations can be performed in the NEN model sketched in Fig. 1: (a) "servicing", i.e. applying time and resources at each node "producer" in order to transfor/assemble input parts into output items; (b) "negotiating", i.e. applying rules at each node "market" in order to send demands for items to each upstream node "producer", directly connected to the market itself; demands are decided depending on both potemtial deliveries and expected item costs.
Both types of operations can really be performed only if each node of the network is endowed with a proper decision-making (DM) autonomy, which can be defined in terms of: • a proper performance goal to be reached; • a proper knowledge of constraints which must be satisfied in order that the global network can survive (also denoted "responsibility"); • a proper set of information concerning oPeEations performed by other nodes in the network. The two concepts of "operations" and of "DM autonomy" intuitively derives from the special net78
To this aim, with reference to the wide literature in the field (see above references, as examples), a specific negotiation model with mediator is here introduced.
work considered: their use implies the definition of each node such as an "agent" in a multi-DM industrial system (Lin & Solberg, 1992; Joshi & Singh, 1999; Krovi, Greasser & Pracht, 1999). The special characteristics of a NEN structure are the following : i) two different types of agents are connected in the network (producer and market); ii) each link is a connection between two agents od different type; iii) each par of (different) agents, if directly connected, are connected by two links with opposite direction and different transmission (items from a producer to the market, bids from the market to the producer) . Depending on the above stated its main features, a NEN can have two complementary definitions .
Mediator(k)
flows
Recei ves a set of demands i & d ik , DDik ~ related duedates [d ik , DD ik ] Oikn, Allocates tasks DDikn (according to proposed duedates d ik , DDik ~
Ft Definition: A NEN is a network of markets. each
Verifies if all demands are satisfied; IF NOT, modifies due-dates of non-accepted demands
one considered with its own set of suppliers and its own set of clients. As a consequence, a NEN can operate only if each market correctly operates by applying a complete negotiation with suppliers and clients. Depending on the negotiation rules, specific evolutions for each market in the network are possible. But a NEN can exist only if the evolutions of all markets inside are coherent, i.e. non-conflicting together.
Producer (n) Sequences all the demands by decreasing "estimated" capacity; Computes service %; Generates possible supplies [Oikn, DD ikn ] As above, but with "effective" capacity
Oikn, DDikn (-
Go back to first line ~
Fig. 2. Sketch of a simple negotiation procedure.
The above sketched procedure is a typical example of negotiation rule through mediator, where all actions are simply summarized by a recursive nonexploding interaction between the market mediator and the connected suppliers. This procedure clearly shows that any negotiation loop aims to generate an equilibrium condition for the considered market. In fact any negotiation loop tries to produce balanced loads for all upstream producers, thus avoiding bottlenecks. In case all nodes market are managed by a mediator, the whole network will operate in equilibrium conditions, reached as soon as every new event (generated by new demands) will be allocated by adapting all market situations (by locally applying the negotiation procedure).
2nd Definition: A NEN is a network of producers. each one operating on several input and output markets, for purchasing and delivering items. As a consequence, a NEN can operate only if each producer correctly operates by purchasing and supplying items at competitive costs. Depending on the competition capabilities, specific evolutions for each producer can arise. But a NEN can exist only if all producers can survive: then a controlled competitive environment must be assured.
rr
Consequence: A controlled competitive environment in a NEN is assured if each market is driven by a "mediator". These considerations can motivate the first Thesis, thus requiring a special management of internal markets in a NEN through mediator (Wiederhold, 1992; Maturana et ai, 1998; Jones & Jasek, 1998).
4. TOPOLOGICAL CONDITIONS FOR THE NEN DESIGN The third Thesis consists in proving that, in a network of partially independent enterprises, conditions showing the convenience to link together two or more enterprises such as to generate a NEN can be stated. According to the previous Thesis, a necessary condition which states that a NEN can be constituted, is the organization of negotiation rules at each node market including a mediator.
3. MODEL OF AN INfERNAL NODE NEGOTIATION The second Thesis aims to show that, in a NEN internal market, an admissible negotiation process trough mediator will generate an equilibrium evolution of the market itself.
79
Based on this consideration, the aim is now to analyze potential connections between two (or more) nodes, and related agents, in such a way to recognize if and when these connections can be convenient.
r' Convenience condition for joining: Considered two producers by which a "tandem service" can be generated, the respective propension to fusion is proportional to the respective expected income increase.
In topological terms, two agents "producer" can be connected together according one of the following two elementary patterns: • Series connection, obtained by linking the two producers such that an intermediate market be input market for the downstream agent and output market for the upstream agent; this connection generates a "supply chain "; • Parallel connection, obtained by linking together two producers such that both have common input and output markets; this connection generates a "tandem service".
Motivation of this condition comes from the topological concept of "tandem" and from the "tandem service" characters. Condition on priority of potential connections: Considered two producers by which a connection can be created, generation of a connection which increases capacity presents a higher priority with respect to generation of supply chains. Motivation for this practical result comes from noting that a "tandem service" implies that both producers will utilize common real services, e.g. common logistics, thus increasing both the production capacity and the save of internal costs.
Each connection presents proper characteristics: A "supply chain" will be characterized by a production capacity equal to the minimum capacity among those of the component producers, and a value of the "product cost" given by the sum of individual respective values of costs at the two producers. A "tandem service" will be characterized by a production capacity given by the sum of individual capacities whilst the product cost will be fixed by the maximum value between the two respective costs at the component producers (Note that this modeling assumption is a balancing nonconflicting condition).
2nd Convenience condition for joining: Considered three producers, denoted A, B, and C, such that: A and B operate towards the same output market; C operates in complete complementarity w.r.t. A, and partial complementarity w. r. t. B; then there exists a clear interest to generate a "supply chain" composed by A and C. This practical result will also come from topological considerations. All previous conditions will be completed by stating another one which specifies impossibility to create local networks but partially connected.
By representing these two potential elementary connections, some topological properties can be recognized: (a) In case two producers are connected into a "tandem service", they can be potentially in competition; (b) In case of "supply chain" connection, the two producers are potentially in co-operation.
rd
3 Convenience condition for joining: Considered three producers which could be connected in parallel, one cannot generate two partial "tandem services", both containing a same producer. An evident motivation prevents from creating such a type of local network: the agent included in both "tandem services" cannot be characterized by different performance goals.
For each one of the potential elementary connections, conditions showing the convenience to generate the connection can be motivated on the basis of the proper characteristics above outlined.
Some remarks: Conditions above stated seem to be sufficient for a complete even if preliminary modelization of a NEN. They give suggestions also for some design lines, namely an initial phase aiming to identify characteristics of potential connections, then a second phase devoted to select more convenient connections, and finally a third phase with the scope of stating the main properties of the resulting NEN. All phases can be performed by applying above conditions and practical results.
Propension to joining: Propension of two producers to joining together depends on (a) local topology, and (b) respective market positions (i.e. difference between expected and real income values, being income given by the difference between negotiated items price and internal standard costs). The propension of connecting together two producers is then conditioned by two factors: the type of connection which can be locally activated, and the expected convenience of each potential partner. 80
management of transients should play the crucial role in NEN development.
5. SOME CONCLUSIONS The considerations presented above seem to present a significant industrial interest for several reasons. First, they offer practical suggestions for developing new network of enterprises by emphasizing the contribution which each potential component could give. As a second remark, such conditions suggest to approach the problem of designing a new industrial entity through a reasonable balance of logistics (that's the real meaning of "topological") reasons and convenience considerations, both integrated together in a common NEN representation . But mainly, all considerations above are motivated by the most important feature of a NEN: its "temporarity ". Being a modular structure. a NEN must be easily generated but also eaSily decomposed and again arranged in another pattern.
Acknowledgements: This research has been partially supported by the Italian Ministry of University and Technological Research , within a national research programme 40%.
REFERENCES Jones, P.M .. and Jasek, c.A. (1998). From distributed supervisory control to enterprise integration: coordination support fro operational environment. Group Decision and Negotiation , Kluwer Academic, The Netherlands, 249-264. Joshi, A., and Singh, M.P. (1999). Multi-agents system on the net. Communications of the A CM, 42, 3. Krovi, R , Graesser, A.c., and Pracht, W.E. (1999). Agent behaviours in virtual negotiation environments . IEEE Transactions on Systems. Men and Cybernetics, SMC-29, 1. Lin, G.y' , and Solberg, J. (1992). Integrated shop floor control using autonomous agents. liE Transactions, 24, 3, 57-71. Mathews, 1. (1995). Organizational foundations of intelligent manufacturing systems - the holonic viewpoint. CIMS Journal , 8, 237-244. Maturana, F., Shen, W., and Norie, D.H. (1998). MetaMorph: an adaptive agent-based architecture for intelligent manufacturing. International Journal of Production Research, 37, 10, 21592173 . Rumbaugh, J. et al (1991). Object-Oriented Modelling and Design, Prentice-Hall, Englewood Cliffs, NJ. Villa, A. (1998). Designing a "network of enterprises" organization : a new approach to enterth prise cooperation. Prepr. 8 IFACIIFORS/IMACS/IFIP Symp. on Large Scale Systems, Patras, Greece. Villa, A. (1999), Organizing a "Network of Enterprises" by object-oriented design", in Preprints IFAC World Congress, Bijing, P.R China. Wiederhold, G. (1992). Mediators in the architecture of future information systems. IEEE Computer, 25, 3, 38-49.
In addition, in order to guarantee the local individual autonomy, the management of a constituted NEN must state: (a) the parameters of negotiation rules, that means the rules according to which survival of each NEN member is assured; Cb) the production and income targets for the whole network. On the other hand, in order to assure easy reconfigurability without crisis, the NEN management must also state: Cc) conditions for an easy "inclusion" of a new NEN member as well as for an easy "separation" of an old NEN member, stated in such a form to prevent hostile actions against the NEN itself but without affecting local autonomy. The three points above outlined are strictly connected together: the first two ones give reason of the motivation of a producer to be a NEN member; the latter is a condition of transparency in the connection. All points can be viewed as consequences of the conditions presented in the previous section. But all points also need to receive a further formulation, to be key factors in a NEN design methodology. Future evolutions of the modeling approach here presented will be devoted to a deeper analysis of the NEN management, with special attention to the transients related to some modification of the NEN compositions. One could expect that an effective
81
ORGANlZA TIONAL STRUCTURES FOR DISTRIBUTED NETWORKS OF ENTERPRISES
Agostino Villa
Dipartimento di Sistemi di Produzione ed Economia dell'Azienda Politecnico di Torino, c.so Duca degli Abruzzi, 24, 10129 - Torino (1taly) Phone: +39-11-564. 7233;fax: -564.7299; e-mail: [email protected]
Abstract: This paper analizes the emerging organizations in business and production denoted "Networks of ENterprises (NEN)", namely organizations generated by a temporary agreement of several firms which aim to cooperate together in a common business area. The aim of the paper is to show how an effective integration of the firms can be obtained through a NEN based on two structural basic elements: by connecting individual firms through "negotiation" interactions, and by managing connections through a "mediator". Both conditions are necessary to state and apply design criteria for a NEN, as well as to assure an efficient performance of the NEN operations. Copyright @2000 IFAC
Keywords: Enterprise, Integration, Organization, Networks
to process proper items and then operate on proper markets. Finally, the NEN agreement can also be used such as a transient situation during which all involved SMEs can verify their effective interest to become a partner in a consortium, for instance, or something else more structured. Owing to its interest, a NEN organization needs to be deeply analyzed and accurately modeled in order to develop methodological tools which could support its design and management. This is the main scope of this paper. The main concept on which all considerations will be based is that a NEN can be graphically represented such as a "graph of services and markets, alternatively connectetf': it means that each node "service" can be only connected with nodes "market" both upstream and downstream, as shown in Fig. 1 (according to an object-oriented representation, as in Rumbaugh et aI, 1991). In practice, this representation emphasizes that, in any network of enterprises, either related together or in competition, input and output flows of each enterprise are always directed from/to a market (Villa, 1999). Based on this idea, the paper will be organized into three Theses to be proved:
1. INTRODUCTION In recent years the globalization of business and production is pushing competitive enterprises to find new types of co-operation in order to maintain their competitiveness worldwide. Among the different types of agreements which can generate effective synergy of partners, a potential organization of enterprises can be originated on the basis of their complementarity. In this case, different enterprises, able to produce parts which can be utilized in similar final products, can give rise to a "virtual enterprise" in terms of a connecting network. More preciselyall enterprises which agree to be included into a NEN, sign an agreement of transparent cooperation in defining common industrial plans for specific products, but can maintain their independence and autonomy for any other production. This type of agreement presents some particular features of direct interest for several Small & Midscale Enterprises (SMEs). On one hand, the agreement can be temporary, because it only involves a part of the core business of any NEN member. On the other, it does not completely reduce the autonomy of each NEN member, since each one can still
77
1SI Thesis: Assumed a graphical representation of a global enterprise organized such as a NEN, then any operation among NEN components is performed in terms of "negotiation" among two or many enterprises having the same downstream market. 2nd Thesis: Assumed a formal model of the "negotiation" with presence of a "mediator" such to generate a non-conflicting allocation of resources/tasks, then each negotiation aims to produce an equilibrium situation among enterprises characterized by balanced production loads. 3rd Thesis: In an equilibrium situation as stated above, the graphical model of a NEN based on negotiation allows to define topological conditions, concerning interactions among enterprises, which states NEN design criteria.
pans connected together and modelled by a network of "objects". In such a network a node can either represent a "producer" (that means an enterprise supplying either components or end items) or a "market" (i.e. a service devoted to manage exchange of items among producers together, and from producers to end users). Note that each time a market drives items to end users, then it operates such as a "sink"; differently a market can only manage transactions among producers. Each node of given type (i.e. producer or market) can receive inputs only from a node of the different type, and the same happens for outputs. Then, a node producer can only receive inputs from nodes market, from which it obtains materials and components to be processed. Any node market can only receive inputs from nodes producers, which send their own end items to the market in order to sell them either to other nodes producers or to end users (final clients). A graphical representation of the concepts above stated is illustrated in Fig. 1.
2. GRAPIllCAL MODEL OF A NEN. Referring to the 1sI Thesis, as stated in (Villa, 1998, and 1999), a NEN can always be represented such as a graph, i.e. through the composition of physical orders
purchase
Demands VsA
Delivery fromB
Fig. 1. Example of simple NEN representation according to graphical modeling ideas. Depending on the two types of nodes, in principle two types of operations can be performed in the NEN model sketched in Fig. 1: (a) "servicing", i.e. applying time and resources at each node "producer" in order to transfor/assemble input parts into output items; (b) "negotiating", i.e. applying rules at each node "market" in order to send demands for items to each upstream node "producer", directly connected to the market itself; demands are decided depending on both potemtial deliveries and expected item costs.
Both types of operations can really be performed only if each node of the network is endowed with a proper decision-making (DM) autonomy, which can be defined in terms of: • a proper performance goal to be reached; • a proper knowledge of constraints which must be satisfied in order that the global network can survive (also denoted "responsibility"); • a proper set of information concerning oPeEations performed by other nodes in the network. The two concepts of "operations" and of "DM autonomy" intuitively derives from the special net78
To this aim, with reference to the wide literature in the field (see above references, as examples), a specific negotiation model with mediator is here introduced.
work considered: their use implies the definition of each node such as an "agent" in a multi-DM industrial system (Lin & Solberg, 1992; Joshi & Singh, 1999; Krovi, Greasser & Pracht, 1999). The special characteristics of a NEN structure are the following : i) two different types of agents are connected in the network (producer and market); ii) each link is a connection between two agents od different type; iii) each par of (different) agents, if directly connected, are connected by two links with opposite direction and different transmission (items from a producer to the market, bids from the market to the producer) . Depending on the above stated its main features, a NEN can have two complementary definitions .
Mediator(k)
flows
Recei ves a set of demands i & d ik , DDik ~ related duedates [d ik , DD ik ] Oikn, Allocates tasks DDikn (according to proposed duedates d ik , DDik ~
Ft Definition: A NEN is a network of markets. each
Verifies if all demands are satisfied; IF NOT, modifies due-dates of non-accepted demands
one considered with its own set of suppliers and its own set of clients. As a consequence, a NEN can operate only if each market correctly operates by applying a complete negotiation with suppliers and clients. Depending on the negotiation rules, specific evolutions for each market in the network are possible. But a NEN can exist only if the evolutions of all markets inside are coherent, i.e. non-conflicting together.
Producer (n) Sequences all the demands by decreasing "estimated" capacity; Computes service %; Generates possible supplies [Oikn, DD ikn ] As above, but with "effective" capacity
Oikn, DDikn (-
Go back to first line ~
Fig. 2. Sketch of a simple negotiation procedure.
The above sketched procedure is a typical example of negotiation rule through mediator, where all actions are simply summarized by a recursive nonexploding interaction between the market mediator and the connected suppliers. This procedure clearly shows that any negotiation loop aims to generate an equilibrium condition for the considered market. In fact any negotiation loop tries to produce balanced loads for all upstream producers, thus avoiding bottlenecks. In case all nodes market are managed by a mediator, the whole network will operate in equilibrium conditions, reached as soon as every new event (generated by new demands) will be allocated by adapting all market situations (by locally applying the negotiation procedure).
2nd Definition: A NEN is a network of producers. each one operating on several input and output markets, for purchasing and delivering items. As a consequence, a NEN can operate only if each producer correctly operates by purchasing and supplying items at competitive costs. Depending on the competition capabilities, specific evolutions for each producer can arise. But a NEN can exist only if all producers can survive: then a controlled competitive environment must be assured.
rr
Consequence: A controlled competitive environment in a NEN is assured if each market is driven by a "mediator". These considerations can motivate the first Thesis, thus requiring a special management of internal markets in a NEN through mediator (Wiederhold, 1992; Maturana et ai, 1998; Jones & Jasek, 1998).
4. TOPOLOGICAL CONDITIONS FOR THE NEN DESIGN The third Thesis consists in proving that, in a network of partially independent enterprises, conditions showing the convenience to link together two or more enterprises such as to generate a NEN can be stated. According to the previous Thesis, a necessary condition which states that a NEN can be constituted, is the organization of negotiation rules at each node market including a mediator.
3. MODEL OF AN INfERNAL NODE NEGOTIATION The second Thesis aims to show that, in a NEN internal market, an admissible negotiation process trough mediator will generate an equilibrium evolution of the market itself.
79
Based on this consideration, the aim is now to analyze potential connections between two (or more) nodes, and related agents, in such a way to recognize if and when these connections can be convenient.
r' Convenience condition for joining: Considered two producers by which a "tandem service" can be generated, the respective propension to fusion is proportional to the respective expected income increase.
In topological terms, two agents "producer" can be connected together according one of the following two elementary patterns: • Series connection, obtained by linking the two producers such that an intermediate market be input market for the downstream agent and output market for the upstream agent; this connection generates a "supply chain "; • Parallel connection, obtained by linking together two producers such that both have common input and output markets; this connection generates a "tandem service".
Motivation of this condition comes from the topological concept of "tandem" and from the "tandem service" characters. Condition on priority of potential connections: Considered two producers by which a connection can be created, generation of a connection which increases capacity presents a higher priority with respect to generation of supply chains. Motivation for this practical result comes from noting that a "tandem service" implies that both producers will utilize common real services, e.g. common logistics, thus increasing both the production capacity and the save of internal costs.
Each connection presents proper characteristics: A "supply chain" will be characterized by a production capacity equal to the minimum capacity among those of the component producers, and a value of the "product cost" given by the sum of individual respective values of costs at the two producers. A "tandem service" will be characterized by a production capacity given by the sum of individual capacities whilst the product cost will be fixed by the maximum value between the two respective costs at the component producers (Note that this modeling assumption is a balancing nonconflicting condition).
2nd Convenience condition for joining: Considered three producers, denoted A, B, and C, such that: A and B operate towards the same output market; C operates in complete complementarity w.r.t. A, and partial complementarity w. r. t. B; then there exists a clear interest to generate a "supply chain" composed by A and C. This practical result will also come from topological considerations. All previous conditions will be completed by stating another one which specifies impossibility to create local networks but partially connected.
By representing these two potential elementary connections, some topological properties can be recognized: (a) In case two producers are connected into a "tandem service", they can be potentially in competition; (b) In case of "supply chain" connection, the two producers are potentially in co-operation.
rd
3 Convenience condition for joining: Considered three producers which could be connected in parallel, one cannot generate two partial "tandem services", both containing a same producer. An evident motivation prevents from creating such a type of local network: the agent included in both "tandem services" cannot be characterized by different performance goals.
For each one of the potential elementary connections, conditions showing the convenience to generate the connection can be motivated on the basis of the proper characteristics above outlined.
Some remarks: Conditions above stated seem to be sufficient for a complete even if preliminary modelization of a NEN. They give suggestions also for some design lines, namely an initial phase aiming to identify characteristics of potential connections, then a second phase devoted to select more convenient connections, and finally a third phase with the scope of stating the main properties of the resulting NEN. All phases can be performed by applying above conditions and practical results.
Propension to joining: Propension of two producers to joining together depends on (a) local topology, and (b) respective market positions (i.e. difference between expected and real income values, being income given by the difference between negotiated items price and internal standard costs). The propension of connecting together two producers is then conditioned by two factors: the type of connection which can be locally activated, and the expected convenience of each potential partner. 80
management of transients should play the crucial role in NEN development.
5. SOME CONCLUSIONS The considerations presented above seem to present a significant industrial interest for several reasons. First, they offer practical suggestions for developing new network of enterprises by emphasizing the contribution which each potential component could give. As a second remark, such conditions suggest to approach the problem of designing a new industrial entity through a reasonable balance of logistics (that's the real meaning of "topological") reasons and convenience considerations, both integrated together in a common NEN representation . But mainly, all considerations above are motivated by the most important feature of a NEN: its "temporarity ". Being a modular structure. a NEN must be easily generated but also eaSily decomposed and again arranged in another pattern.
Acknowledgements: This research has been partially supported by the Italian Ministry of University and Technological Research , within a national research programme 40%.
REFERENCES Jones, P.M .. and Jasek, c.A. (1998). From distributed supervisory control to enterprise integration: coordination support fro operational environment. Group Decision and Negotiation , Kluwer Academic, The Netherlands, 249-264. Joshi, A., and Singh, M.P. (1999). Multi-agents system on the net. Communications of the A CM, 42, 3. Krovi, R , Graesser, A.c., and Pracht, W.E. (1999). Agent behaviours in virtual negotiation environments . IEEE Transactions on Systems. Men and Cybernetics, SMC-29, 1. Lin, G.y' , and Solberg, J. (1992). Integrated shop floor control using autonomous agents. liE Transactions, 24, 3, 57-71. Mathews, 1. (1995). Organizational foundations of intelligent manufacturing systems - the holonic viewpoint. CIMS Journal , 8, 237-244. Maturana, F., Shen, W., and Norie, D.H. (1998). MetaMorph: an adaptive agent-based architecture for intelligent manufacturing. International Journal of Production Research, 37, 10, 21592173 . Rumbaugh, J. et al (1991). Object-Oriented Modelling and Design, Prentice-Hall, Englewood Cliffs, NJ. Villa, A. (1998). Designing a "network of enterprises" organization : a new approach to enterth prise cooperation. Prepr. 8 IFACIIFORS/IMACS/IFIP Symp. on Large Scale Systems, Patras, Greece. Villa, A. (1999), Organizing a "Network of Enterprises" by object-oriented design", in Preprints IFAC World Congress, Bijing, P.R China. Wiederhold, G. (1992). Mediators in the architecture of future information systems. IEEE Computer, 25, 3, 38-49.
In addition, in order to guarantee the local individual autonomy, the management of a constituted NEN must state: (a) the parameters of negotiation rules, that means the rules according to which survival of each NEN member is assured; Cb) the production and income targets for the whole network. On the other hand, in order to assure easy reconfigurability without crisis, the NEN management must also state: Cc) conditions for an easy "inclusion" of a new NEN member as well as for an easy "separation" of an old NEN member, stated in such a form to prevent hostile actions against the NEN itself but without affecting local autonomy. The three points above outlined are strictly connected together: the first two ones give reason of the motivation of a producer to be a NEN member; the latter is a condition of transparency in the connection. All points can be viewed as consequences of the conditions presented in the previous section. But all points also need to receive a further formulation, to be key factors in a NEN design methodology. Future evolutions of the modeling approach here presented will be devoted to a deeper analysis of the NEN management, with special attention to the transients related to some modification of the NEN compositions. One could expect that an effective
81