## 4 Conclusion
To achieve this, CUSTOMER A creates a barter request. This barter request is sent to the Matchmaker agent which uses each service's own ontology to send the customer a list of the most appropriate semantic web services. In this way, the agent gets semantically close services that accommodate the agents providing the needed product. However, till this point of the scenario, no agent has been introduced to the system before, so if CUSTOMER A agent finds appropriate services, these services will not return any agents that CUSTOMER A can barter. Therefore, CUSTOMER A will be registered to an appropriate service and wait for the new agents to be added to the system. In this scenario, after CUSTOMER A, CUSTOMER B and CUSTOMER C agents are involved in the system. The requirements of the CUSTOMER B are the same as the CUSTOMER A, except for the lower and upper limits that the CUSTOMER A determines for bartering. In this case, CUSTOMER B would register to a suitable service because it will not find a suitable agent for bartering. The CUSTOMER C agent offers \"netbook\" and requests \"coconut\", unlike CUSTOMER A and CUSTOMER B. Therefore, a semantic web service, which is found by the Matchmaker agent, sends suitable agents for bartering to CUSTOMER C. In this case, CUSTOMER A and CUSTOMER B are the suitable agents for CUSTOMER C.

At this point, the negotiation between agents starts. First, CUSTOMER C sends a proposal to CUSTOMER A. However, as seen in Line (A) of Figure 9, the CUSTOMER A rejects this offer because the offer sent by the CUSTOMER C is higher than the upper limit of the CUSTOMER A. Then, CUSTOMER C sends the same proposal to the CUSTOMER B. Since the proposal is in the acceptable range of CUSTOMER B, the negotiation between them begins and eventually, an agreement was reached by these two agents as shown in Line (B) of Figure 9.

## 5 Related Work

The work conducted in this study is mainly related with two research fields: MAS development methodologies and e-barter systems. Hence, in the following, we first discuss the efforts given on deriving MAS development methodologies as similar to our proposal and then give some noteworthy studies on developing e-barter systems which especially consider employing agents. There are various AOSE methodologies which can be used for the development of MAS. Methodologies such as ADELFE [41], Gaia [42], INGENIAS [43], PASSI [44], Prometheus [45] and Tropos [46] provide systematic processes including analysis and design of agent systems. It is also possible to integrate the outcomes of these methodologies with various agent execution platforms/frameworks such as JADE [18], JACK [20], Jason [47], CArtAgO [48], MOISE [49] and JaCaMo [50] to implement designed agents. However, neither of these methodologies nor platforms directly support model-driven MAS development. In fact, re-engineered and improved versions of some of these methodologies (e.g., [51] for ADELFE, [52] for INGENIAS, [53] for Prometheus, [54] for Tropos) enable MAS development according to MDD paradigm as indicated in [55]. Although MAS modeling from different viewpoints and code generation for various agent platforms are also covered in these updated methodologies, model-driven development of semantic web services and interactions between agents and these semantic web services are not included. Moreover, an iterative process supporting modeling and implementation are not considered and it is too difficult to modify intermediate models and update auto-generated codes by using most of these methodologies. The only exception is INGENIAS, which deems supporting the iterative development and modification of models and codes as similar to the MDD methodology proposed in this study. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Name** & **Need** & **Offer** & **Lower Limit** & **Upper Limit** \\ \hline CUSTOMER A & netbook & Coconut & 150 & 200 \\ CUSTOMER B & netbook & Coconut & 200 & 250 \\ CUSTOMER C & coconut & Netbook & 0.0045 & 0.0048 \\ \hline \hline \end{tabular}
\end{table}