The term "middleware" is defined by one's point of view. Many interesting categorizations exist, all centered around sets of tools and data that help applications use networked resources and services. Some tools, such as authentication and directories, are in all definitions of middleware. Other services, such as coscheduling of networked resources, secure multicast, object brokering, and messaging, are the particular interests of certain communities, such as scientific researchers or business systems vendors. This breadth of meaning is reflected in the following working definition: Middleware is "the intersection of the stuff that network engineers don't want to do with the stuff that applications developers don't want to do."