Abstract:    The platform business model under the Internet has been applied in more and more fields. This paper uses case study methods to explore the value creation logic of platform business models in the Internet context. We draw on the relevant ideas of the value network model and combine the value creation theory and the main features of the platform business model, and describe the basic modules of the platform business model from the six main aspects (that is, "participants", "external requirements", "value proposition", "key business", "core resources", "profit model"). According to the mutual relationship of the six modules, a network model for the value creation of platform business models in the Internet context is constructed. The explanation of the six main modules is as follows.
   Participants: In a platform-based business model, participants can be customers, partners, vendors, and other stakeholders. Usually, there is an interdependent and mutually reinforcing "positive feedback" feature among the various stakeholders involved in the platform, which is one of the key factors for the value creation of the platform business model. External requirements: Dynamic changes in the external market environment, industrial environment, and technological innovations may all pose new demands on enterprises. There are often intricate relationships between external influences and dynamic changes in consumer demand. Value proposition: The value proposition explains to some extent the reasons why consumers buy enterprise products or services, and confirms the practical significance of enterprises to consumers. Key business: The key business is to ensure that the business model is practical and the most important thing the company must do. The goal of key business is to create value for the service. Core resources: Core resources are the most important factors to make the business model work, such as intellectual assets, human resources, financial assets, and key technologies. Profit model: The profit model is the way that the business model obtains income, which may include advertising fees, rental fees, usage fees, product sales, and the like. In addition, while obtaining income, different pricing mechanisms can be adopted according to the actual situation of the platform, such as fixed pricing and dynamic pricing. 
    In the research process, due to the large time span and the complex relationship between the elements of the business model, the method of case study is adopted. Alibaba is an enterprise that entered the Internet platform earlier in China, which has formed a huge business ecosystem. Its successful experience has a good reference for the development of many other platform-based enterprises. Therefore, this study chooses Alibaba as the case study. Based on a comprehensive analysis of the development process of Alibaba, the development process of the Alibaba is divided into three main stages, namely the start and development stage (1999-2003), the transition and expansion stage (2004-2010), the maturity and prosperity stage (Since 2011).
This paper studies the value creation logic of Alibaba in the three development stages by using the network model of value creation. In the first phase, Alibaba concentrated its core resources to develop an Internet trading platform that focuses on the provision and integration of information flow and is committed to solving various obstacles in the traditional business model. In the second phase, Alibaba′s business scope has expanded to multiple areas, and its external needs are more complex, with more participants, more diverse types, and more extensive coverage. At the same time, compared with the first stage, the profit model of this stage has made a new breakthrough, and the model and channel of value creation are also more abundant. In the third stage, supported by e-commerce platform, Alibaba has formed a huge business ecosystem by centering on the core e-commerce business and the payment business and finance business supporting the e-commerce system, as well as supporting local life services, medical and health care, digital media, entertainment business and intelligent terminals. The speed, breadth and depth of its value creation have far exceeded the traditional business model.
    Based on the comprehensive analysis of the evolution process of Alibaba′s business model in different development stages, the results show that: Firstly, the more of Internet platform participants, the richer of types and the wider of coverage area, the easier it is to form a closely connected value network, which helps Internet platform enterprises realize value growth. Secondly, capturing external demand in real time and taking timely countermeasures can promote the platform to create new value. Thirdly, diversified Internet platform enterprises should be supported by core business and radiate the development of other businesses. With the change of external demand, core supporting business needs to keep pace with the times and constantly adapt to the changing external environment. Fourthly, the business ecosystem supported by the Internet platform can promote the platform value in all directions from multiple fields. 
   We draw the following management enlightenment: Firstly, the Internet platform not only needs to acquire users, but also needs to retain users. Platform companies can attract users in a variety of ways. In addition, platform companies should establish operating mechanism to improve user satisfaction and improve users′ dependence on platform products or services. Secondly, Platform companies need to actively foster their own dynamic capabilities to accurately capture external requirements. While the Internet platform continuously provides content that meets users′ expectations, it also needs to update itself and capture new user demands. Thirdly, Internet platform companies should put the development of core support business in the first place. In addition, diversified platform companies should prioritize the expansion of their core business-related areas in the expansion of their business scope. On the one hand, the core business has a radiant role to the related business, on the other hand, the related business has a deepening role to the core business. Fourthly, drive the value creation of the Internet platform with a range economy. Internet platform enterprises should not only pay attention to the development of their own fields, but also pay attention to other areas related to them. The platforms cooperate and develop together to create a mutually beneficial ecosystem.

Key words: platform, business model, internet, value