Intercomputer communications

A group of computers becomes a network when intercomputer communication is estabhshed. Prior to the 1980s, all system suppliers used proprietaiy protocols to network their systems. Ad hoc approaches were sometimes used to connect third-pai ty equipment, which was not cost-effective in system maintenance, upgrade, and expansion. The recent introduction of standardized protocols has led to a decrease in initial capital cost. Most current DCS network protocol designs are based on the ISO-OSI seven-laver model. 

Introduction of XML formats was a very important step toward better intercomputer communication, but it is not a miraculous solution to all problems. Not every possible relation is easily expressed in XML (Wang et al. 2005), so specifications usually contain many implicit assumptions that are not properly formalized. The Resource Description Framework (RDF) provides a very powerful yet simple model for this formalization (Manola and Miller 2004). In this framework, any information is transformed to basic units called triplets that are combined to map the available information. This unifying mechanism can be used to express hierarchical vocabularies for domain knowledge description, as in RDF Schema (Brickley and Guha 2004) or its extension, Web Ontology Language (OWL) (Smith et al. 2004), both standardized by the W3C. 

Protocol A description of the messages and rules for interchanging messages in intercomputer communication. 

A group of computers can become networked once intercomputer communication is established. Prior to the 1980s, all system suppHers used proprietary protocols to network their systems. The recent introduction of standardized protocols is based on the ISO-OSI seven-layer model. The manufacturing automation protocol (MAP), which adopted the ISO-OSI standards as its basis, specifies a broadband backbone local area network (LAN). Originally intended for discrete component systems, MAP has evolved to address the integration of DCSs used in process control as well. TCP/IP (transmission control protocol/internet protocol) has been adopted for communication between nodes that have different operating systems. 

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