In this paper, we show that Service Oriented Architectures enable exchanges to be more flexible inside the virtual enterprise (VE), because they create an electronic market-place between the actors composing the VE. However, mechanisms have to be settled to regulate exchanges inside the VE, as well as to protect the VE from external threats and aggressions. Those mechanisms can be materialized by Service Level Agreements (SLA) aiming to define criterion evaluating the quality of exchanges (products and services) inside the VE. This SLA definition is very important, because it will guarantee the good transaction operations between actors. In very specific and wellknown fields, an automatic SLA creation can be considered, which would enable to perform transactions between actors in an automated way. At last, we propose a simple solution based on the auction principle to match offer and demand in the market-place.
In a more and more globalized context where competition is hard, sometimes
enterprises have to make alliances to be able to answer to a specific market. It is
therefore necessary that different actors (enterprises) regroup themselves to answer to
a common project. Despite obvious advantages that an inter-enterprise collaboration
has to offer, to settle efficient collaboration is not obvious ([
Today, global mastery of inter-organization processes is not reached yet, and
interoperability problems between information systems (IS) is an effervescent field
[
SOA is an interesting concept to make communication between enterprises easier
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In this paper, we explain why “universal” interoperability, which is potentially possible thanks to SOA is important and changes the way we handle Information Systems. Then, we explain why it is necessary to control ad-hoc exchanges between Information Systems and to design and settle regulation mechanisms managing the VE evolution. Then, we show that the exploitation of a regulation system thanks to Service Level Agreements (SLA) in the VE must be done on several decisional levels (operational, tactical, strategical), to handle the management of all informations, and to reduce the complexity of the global system. We show how an accurate SLA definition allows to improve interoperability without damaging the quality of service. At last, we propose a solution based on the auction mechanism enabling to perform exchanges of goods and services between actors of the VE.
2.1.
When actors of a virtual enterprise want to communicate, most of the time they
settle specific networks for exchanging information (figure 1).
This gives as a result an ad-hoc network of exchanges, which can quickly become
very complex. Such an architecture can be called a spaghetti architecture [
SOA is a logical architecture of the Information System resting on the concept of “service”. The service is the basic element and the keystone of the architecture. Services Oriented Architectures (SOA) enable to better structure information exchanges between enterprises IS, which allows the actors having the will to interact to offer services which can be invoked by other actors. Besides, each entity of the VE is plugged on the enterprise service bus (ESB). SOA are very interesting when talking about virtual enterprises. SOAs offer flexibility when an actor wants to join or leave the VE. When he joins the VE, he plugs himself on the Bus and can access the proposed services. When he leaves the VE, he unplugs himself from the bus. Each actor who is present on the bus can be aware of the other's actions (thanks to a global directory), and therefore can re-configure his system. Besides, the ESB connexion can allow to create alliances more easily, the bus becomes the backbone of all exchanges, that is to say a market-place, because all the actors of the VE join it either to buy or to sell something : a service, an information, or a product.
We will define the concept of market-place in a simple way. For us, it is the place, real or virtual, where the offer is trying to meet the demand, at the right price (the price depends on the offer and on the demand). SOAs offer the possibility to create a market-place between all the actors of the virtual enterprise. Indeed, a seller only needs to publish what he sells, and the other actors connected on the bus are aware of it, thanks to the global directory referencing all the offered services present on the bus. In the same way, a buyer can publish what he wants to buy, so that all the actors present on the bus are aware of it. Everything can be sold or bought : goods, informations, resources.... This fact is not a revolution in the business field, but SOAs give the possibility to standardize exchanges, to make them much more easier and faster. ESBs used as market-place will lead to exchanges fluidification and standardization.
SOA should enable to standardize exchanges of all kind between the actors of the virtual enterprise. However, these electronic market-places inside the VE will regroup any kind of goods or services to sell: available room in a transportation mean, production resources, human resources, products... There is a need, to use SOA and ESBs as a market-place, to establish a framework for exchanges, to determine what are the criterion which will establish the price of something to sell (product quality, delivery time...). SOA enable to exploit all the enterprise's patrimony.
We have seen in the former section that there is a need of standardization about the criterion characterizing the goods in order to simplify the exchanges. But there is also a need of regulation of relations inside the virtual enterprise.
The EV construction happens because of a specific need, which represents a market-logic and it is necessary to settle regulation mechanisms. Indeed, it is not good for the VE's operation that an actor leaves the virtual network too quickly, because such a behavior can jeopardize the whole network. In the same way, a virtual network can not accept any kind of actor, especially if he does not offer satisfying guarantees. We think that it would be relevant to settle Service Level Agreement (SLA) between actors of the virtual enterprise, to regulate the network modifications e.g. to stop brutal withdrawals or unexpected connections to the bus. Besides, SLA would enable to standardize the belonging criterion to the VE, to protect it from aggressions coming from external competitors. In some way, SLA enable to settle “solidarity” rules between VE's actors, and offer guarantees of sustainability of the VE configuration, even if flexibility possibilities are still present. To summarize, regulation is based on exchanges criterion standardization between the VE's actors. On the other hand, it is based on contracts (SLA) inside the network, which enable to cope with difficult cases (for example brutal withdrawal) which could endanger the virtual enterprise. 3.3
We can notice that if the field in which the exchanges take place is quite well-known, and if the indicators characterizing the good system operations are also well-known and are reliable, then it is possible to generate service contracts in an automated way, by using templates for example. This is of great interest in a more and more competitive environment where the rapid definition and construction of virtual enterprises will determine the actor's survival. In this case, SOA would enable to perform automatic trading of resources or services between actors. However, it is important to notice that it will only be possible in standardized fields, and this method will not be able to be generalized to the whole enterprise. 4
We assume here that the exchanges criteria between actors are standardized. Then, we need to find solutions to match the offer and the demand which exist on the bus. On a classical market-place, the price of the offer is defined by stockbrokers in function of the state of the offer and of the demand. If the demand is high and the offer is weak, prices explode, whereas if the offer is important and the demand low, they crash. In our opinion, such a market-place mechanism is not adapted to regulate exchanges in Service Oriented Architectures. Thus, classical market-places are built to exchange goods (stock or derived products) in huge amount, those exchanges being very quick. In our case, we will rather try to establish long-term trust relationships between actors of the distributed system, even if these relations should evolve considering the market state. Besides, we must not forget that behind a transaction, there are people who will work together or stop working together, and it is important that a trust relationship exist between these actors, in both case of union or separation.
The auction mechanism seems to us more adapted to our situation, because the time scale of auctions is closer from the “human” time scale which is necessary to the good operation of collaborations. The auction fully imply actors offering and demanding. This a bilateral relationship, closer to a collaborative aspect than in a classical market place where the first arrived is the first served. Auctions privilege competition, whereas each actor has his own chance. Each transaction in our system would be evaluated by both the offering and demanding sides, as on Ebay.com. In this manner, a bad actor would exclude himself of the network, because the other actors would not work with him anymore because of his bad evaluations.
The mechanism of evaluated auctions is not perfect. It is thus possible for a group of partners to create collusions, for example by leaving plenty of good evaluations to each others concerning low importance transactions, which will attract other actors, because of the positive general feedback. This would break the fact that the evaluation system is impartial, and the evaluation system is interesting only if it is neutral. To avoid that kind of problem, we could anonymise the actors participating to all the transactions, that is to say that an actor would not know with who he is dealing with. He would only know its “partners” evaluations and the services or goods they are proposing, and nothing else. Thus, when a transaction is ending, actors leave an evaluation only according to the transaction’s quality. To do so, we could settle a special service in charge of anonymising all the actors participating to transactions.
The auction mechanism can be interesting to help to settle collaborations which will be afterwards regulated by SLAs, which are in charge of normalizing the collaboration, and avoiding accidents.
We have seen in this paper that SOA will enable to create electronic market-places between the virtual enterprise's actors, this will increase the exchanges flexibility. However, this fluidity should be handled with care, and it is necessary to settle regulation mechanisms, between the enterprise's actors, but also between the virtual enterprise and the “external world”. This regulation, which can be formalized thanks to Service Level Agreements, aims on one hand to bring more clarification in exchanges, and on the other hand to protect the virtual enterprise from aggressions coming from external competitors.
Service Level Agreements are fundamental for exchanges regulation in the virtual enterprise, but they should not interfere with the exchanges fluidity generated by SOAs. For well-known fields in the enterprise, it could be possible to generate contracts automatically, thanks to reliable indicators, which would enable to perform some transactions automatically between actors. To establish the indicators enabling to elaborate service level agreements is a huge task which needs to be handled very carefully. Indeed, indicators will vary from a field to another, but it will be necessary to take into account the miscellaneous horizons when designing the contracts (operational, tactical, strategical). Besides, if the contracts are here to regulate the exchanges, they play a fundamental evaluation role between actors, and this will enable to promote actors offering good products or services in the virtual enterprise, and on the contrary to penalize the actors who are not that efficient. An auction mechanism can be used to match the offer and the demand. In this context, auctions seem more adapted to us than a classical market-place mechanism where that is the stockbroker who matches the demand with the offer and defines the prices. An important work must be done to settle evaluation mechanisms, to prevent or to stop fraud and collusion attempts between actors, to be able to guarantee exchanges integrity, and thus to ensure the survival and the good operation of the virtual enterprise.