There is considerable confusion in the literature between a computer network
and a distributed system. The key distinction is that in a distributed system, a
collection of independent computers appears to its users as a single coherent system. Usually, it has a single model or paradigm that it presents to the users. Of-
ten a layer of software on top of the operating system, called middleware, is
responsible for implementing this model. A well-known example of a distributed
system is the World Wide Web. It runs on top of the Internet and presents a
model in which everything looks like a document (Web page).
network of networks.