Case Study 2 – Contexts and efficiency/effectiveness balance

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This case study presents two main goals: testing the influence of the efficiency/effectiveness management in ALBidS, and demonstrating the importance of the context definition for the system’s performance. To do so, three simulations using the test scenario are presented. In the first one, Seller 2 uses ALBidS with no contexts and a 100%

preference for effectiveness. In the second, the preference for effectiveness is maintained at its maximum, but this time using context definition. To ease the understanding of the results, the contexts are defined using only two clusters for the day analysis. This way the only separation of contexts is week days, and weekends. In the third simulation, the context definition is equal to the second, but this time the preference goes 100% for efficiency.

Figures 4.7, 4.8 and 4.9 present the definitions for Seller 2’s use of ALBidS for the first, second, and third simulations, respectively.

Figure 4.7 – ALBidS definitions for Seller 2, for the first simulation.

As mentioned, the first simulation does not include the Context Analysis mechanism. However, it includes all supported strategies, with the efficiency/effectiveness balance at the higher preference for effectiveness.

Figure 4.8 – ALBidS definitions for Seller 2, for the second simulation.

Regarding the second simulation, the ALBidS definitions are exactly the same as in the first simulation, except for the use of the Context Analysis mechanism. This mechanism considers, for this case, only the clustering by two periods and two days.

Figure 4.9 – ALBidS definitions for Seller 2, for the third simulation.

In this case the Context Analysis mechanism is active, but the efficiency/effectiveness balance preference is attributed entirely to the efficiency.

Figure 4.10 presents the incomes obtained in each of the three simulations, along 61 simulated days, for the twelfth period of the day. The starting day for these simulations is Monday October 4^th, to facilitate the spotting of both, working days, and weekend days, in the graphs.

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b)

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Figure 4.10 – Incomes obtained by Seller 2 in the twelfth period of the considered 61 days, in: a) the first simulation, b) the second simulation, c) the third simulation.

Analyzing the chart presented in Figure 4.10 a), the pattern concerning the weekend days results is clearly visible. The achieved incomes are always much lower on weekends than during working days. This tendency is softened slowly over the days, but never completely. This is due to the consideration of all days in the same way, not taking into account the different characteristics that weekend days present.

This is visible by analyzing Figure 4.10 b), which by considering weekend days as a different context, and consequently treating these days independently from the rest, manages to get better results on weekends, with no degradation of the results of the business days. Looking closely at this graph, it is visible that the results improvement on weekends starts on the second weekend and continues improving until the end of the simulation

days. Regarding the first weekend (days 6 and 7) presents weak results, since the strategies stats for this context are still in an initial point, i.e., as initialized. This is easily visible by Figure 4.11, which presents the comparison of the incomes of Seller 2 in the first and second simulations.

Figure 4.11 – Incomes obtained by Seller 2 in the first and second simulations, for the twelfth period of the considered 61 days.

Concerning the third simulation, since the full preference is given to the efficiency of the method and not on its effectiveness, the results are much more unstable. However, it is still possible to see in Figure 4.10, the weekends’

worst results pattern in the beginning of the simulation, which is softened throughout the days, to the point that at the end it is almost imperceptible. This is due to the context definition, even with a low preference for effectiveness.

The comparison of the total incomes achieved by Seller 2 in the three simulations, in the total of the 61 days for the considered period is presented in Figure 4.12.

Figure 4.12 – Total Incomes obtained by Seller 2 in the twelfth period of the considered 61 days.

These results show the advantage of using context analysis to define the negotiating behaviour, since the simulation that used it – Simulation 2 is the one that achieved higher incomes. Regarding the third simulation, its preference for efficiency over effectiveness originated the achievement of worst incomes. However, this is compensated by the advantage in processing time, as presented in Table 4.1.

Table 4.1 – Average execution times of the three simulations for one negotiation period, presented in milliseconds.

The results presented in Table 4.1 are clear in what concerns the difference of execution times when using ALBidS with full preference for efficiency or effectiveness, as supported by the difference between Simulation 3 and the other two.

Regarding the difference between the first and second simulations, which refers to the use of the context analysis, it is minimal, taking into account the amount of the values.

This case study allowed showing the advantage of using the context definition, through the demonstration of the achievement of best incomes using this tool. It also presented the adequacy of using the efficiency/effectiveness management, to drastically decrease the simulation executing times, while still achieving good results.