With the advancement of enterprise information system, Services-Oriented Business Ecosystem (SOBE) has become an important pattern for the organization and management of the massive business services. At the same time, Internet Of Service (IOS) provides a business model in which service vendors and consumers can interactive with each other via the Internet. This paradigm makes it possible that services in SOBE be managed in an autonomous and coordinated manner. The challenge here is to really coordinate the distributed services and federate them to achieve the benefits of SOA. To address these shortcomings, this paper presents \"BSNet\", a formal model of the SOBE. The model consists of a three-layer business service correlation network which describes the relationships in SOBE.