Chooses which of multiple components with the same interface to invoke 选择调用多个具有相同接口的组件中的哪一个。
2.
Grid services can maintain internal state to distinguish one instance of a grid service from another that provides the same wsdl interface 网格服务可以维护服务生命周期的内部状态(以便把一个服务实例与另一个提供相同接口的服务实例区分开) 。