Distributed systems are computer systems consisting of a set of nodes connected by communications channels. The most familiar distributed system is, of course, the Internet, which consists of millions of computers connected by communications networks implemented with wires, optical fibers and microwave radio. Protocols such as TCP/IP and HTTP define how data are moved between nodes of the network. The network itself is quite complex, using computers to perform essential communications functions such as routing, name lookup, and error correction. To model a distributed system we abstract away details of the network and its protocols, and model nodes as concurrent processes and communications networks as channels over which processes can send and receive messages.
The most widely used formalism for modeling distributed systems is called Communicating Sequential Processes (CSP), after a 1978 article by that name, written by C.A.R. Hoare . CSP was the inspiration for the communications constructs in several programming languages such as OCCAM and ADA, as well as for the channel construct in PROMELA.
KeywordsBoolean Function Channel Capacity Channel Variable Message Type Communicate Sequential Process
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