Encyclopedia of Computer Science and Technology

426 Shannon, Claude E.Service-oriented architecture is a new approach thatfocuses on services (basic functions, such as displayingand processing forms or formatting data) and providesstandardized ways for them to be accessed by programs.Applications in turn are then built up by “plugging in” therequired services and organizing them to meet the requiredlogic and sequence of processing.In order to be accessed, each service provides “metadata”(usually in XML files) that describes what data isused by a service and what it provides. The descriptionitself can be provided using Web Services Description Language(WSDL), including network addresses (ports) forconnecting to the service, the operations supported, andthe abstract format of the expected data. (For more on themessage protocol, see soap.)There are three basic roles that must be filled in designingan SOA system: The service provider creates a service(often a Web service) and “exposes” aspects of the serviceand controls access to it (through security policies). Theservice broker provides a registry of available services andtells requesters how to connect to them. (For more on brokers,see corba.) Finally, the requestor in an applicationfinds and requests services as needed.In general SOA can be seen as part of the trend towarddecentralized, loosely coupled computing (see distributedcomputing). Because all services communicate throughthe network, it is easy to reallocate or scale up services asneeded. It is also easier to upgrade software and reuse it fornew applications. (For more on combining services providedby applications, see mashups.) However, SOA bringschallenges of its own in terms of making services trulyinteroperable and conforming to standards that are stillevolving.went on to make important contributions to the young disciplineof artificial intelligence (AI).Shannon was born in Gaylord, Michigan, on April 30,1916. He received bachelor’s degrees in both mathematicsand electrical engineering at the University of Michigan in1936. He went on to MIT, where he earned a master’s degreein electrical engineering and a Ph.D. in mathematics, bothin 1940. Shannon’s background thus well equipped himto relate mathematical concepts to practical engineeringissues.While a graduate student at MIT, Shannon was incharge of programming an elaborate analog computercalled the Differential Analyzer that had been built byVannevar Bush (see analog computer and Bush, Vannevar).Actually “programming” is not quite the rightword: To solve a differential equation with the DifferentialAnalyzer, it had to be translated into a variety of physicalsettings and arrangements of the machine’s intricate electromechanicalparts.The Differential Analyzer was driven by electrical relayand switching circuits. Shannon became interested in theunderlying mathematics of these control circuits. He realizedthat their fundamental operations corresponded to theBoolean algebra he had studied in undergraduate mathematicsclasses (see Boolean operators). It turned out that theseemingly abstract Boolean AND, OR and NOT operationshad a practical engineering use. Shannon used the resultsof his research in his 1938 M.S. thesis, titled “A SymbolicAnalysis of Relay and Switching Circuits.” This work washonored with the Alfred Nobel prize of the combined engineeringsocieties (this is not the same as the more famousNobel Prize).Further ReadingErl, Thomas. SOA Principle of Service Design. Boston: Pearson Education/PrenticeHall, 2007.Hurwitz, Judith, et al. Service Oriented Architecture for Dummies.Hoboken, N.J.: Wiley, 2007.Josuttis, Nicolai M. SOA in Practice: The Art of Distributed SystemDesign. Sebastapol, Calif.: O’Reilly, 2007.QAT SOA Resource Center. Available online. URL: http://www.soaresourcecenter.com/. Accessed November 14, 2007.Service-Oriented Architecture (SOA). TechRepublic. Availableonline. URL: http://search.techrepublic.com.com/search/Service-Oriented+Architecture+( SOA).html. Accessed November14, 2007.Weerawarana, Sanjiva, et al. Web Services Platform Architecture.Upper Saddle River, N.J.: Prentice Hall PTR, 2005.Shannon, Claude E.(1916–2001)AmericanMathematician, Computer ScientistThe information age would not have been possible withouta fundamental understanding of how information couldbe encoded and transmitted electronically. Claude ElwoodShannon developed the theoretical underpinnings for moderninformation and communications technology and thenClaude Shannon developed the fundamental theory underlyingmodern data communications, as well as making contributions tothe development of artificial intelligence. (Lucent TechnologiesBell Labs)