5. Conclusions and remarks
WOM marketing processes with both positive and negative comments have been modeled as the SIPNS model, and a measure of the overall profit of WOM marketing campaigns has been proposed. The SIPNS model has been shown to admit a unique equilibrium, and the impact of different factors on the equilibrium has been determined. Furthermore, extensive experiments have shown that the equilibrium is much likely to be globally attracting. Finally,the influence of different factors on the expected overall profit has been ascertained. On this basis, some promotion strategies have been suggested. Toward this direction, lots of efforts are yet to be made. It is well known that the structure of the WOM network has significant influence on the performance of a viral marketing [35, 36]. The proposed SIPNS model is a populationlevel model and hence does not allow the analysis of this influence. To reveal the impact of the WOM network on the performance, network-level spreading models [37–40] or individual-level spreading models [41–47] are better options. The profit model presented in this paper builds on the uniform-profit assumption. However, in everyday life different products may have separate profits. Hence, it is of practical importance to construct a non-uniform profit model. Also, a customer may purchase multiple items a time, and the corresponding model is yet to be developed. Typically, WOM marketing campaigns are subject to limited budgets. The dynamic optimal control strategy against malicious epidemics [48–52] may be borrowed to the analysis of WOM marketing so as to achieve the maximum possible net profit.
