Encyclopedia of Computer Science and Technology

310 middlewareBott, Ed, Carl Siechert, and Craig Stinson. Microsoft Windows VistaInside Out. Redmond, Wash.: Microsoft Press, 2007.Minasi, Mark, and Byron Hynes. Administering Windows VistaSecurity: The Big Surprises. Indianapolis: Wiley/SYBEX, 2007.Simpson, Alan. Alan Simpson’s Windows XP Bible. 2nd ed. Indianapolis:Wiley, 2005.———. Alan Simpson’s Windows Vista Bible. Indianapolis: Wiley,2007.Smith, Ben, and Brian Komar. Microsoft Windows Security ResourceKit. 2nd ed. Redmond, Wash.: Microsoft Press, 2005.“Windows Products and Technologies History.” Microsoft. Availableonline. URL: http://www.microsoft.com/windows/WinHistoryIntro.mspx. Accessed August 15, 2007.middlewareOften two applications that were originally created for differentpurposes must later be linked together in order toaccomplish a new purpose. For example, a company sellingscientific instruments may have a large database of productspecifications, perhaps written in COBOL some years ago.The company has now started selling its products on theInternet, using its Web server and e-commerce applications(see e-commerce). Prospective customers of the Web siteneed to be able to access detailed information about theproducts. Unfortunately, the Web software (perhaps writtenin Java) has no easy way to get information from the company’sold product database. Rather than trying to convert theold database to a more modern format (which might taketoo long or be prohibitively expensive), the company maychoose to create a middleware application that can mediatebetween the old and new applications.There are a variety of types of middleware applications.The simplest and most general type of facility is the RPC(Remote Procedure Call), which allows a program runningon a client computer to execute a program running on theserver. DCE (Distributed Computing Environment) is amore robust and secure implementation of the RPC conceptthat provides file-related other operating system services aswell as executing remote programs.More elaborate architectures are used to link complexapplications such as databases where a program running onone computer on the network must get data from a server.For example, an Object Request Broker (ORB) is used in aCORBA (Common Object Request Broker Architecture) systemto take a data request generated by a user and find serverson the network that are capable of fulfilling the request(see coRBA).Middleware is often inserted into a program to allowfor better monitoring or control of distributed processing.For example a TP (transaction processing) monitor is amiddleware program that keeps track of a transaction thatmay have to go through several stages (such as point of saleentry, credit card processing, and inventory update). TheTP monitor can report whether any stage of the transactionprocessing failed (see transaction processing).Middleware can also be put in charge of load balancing.This means distributing transactions so that they are evenlyapportioned among the servers on the network, in order toavoid creating delays or bottlenecks.While use of middleware may not be as “clean” a solutionas designing an integrated system from the bottom up, theeconomic realities of a fast-changing information environment(particularly with regard to deployment on the Web)often makes middleware an adequate second-best choice.Further ReadingBritton, Chris, and Peter Bye. IT Architectures and Middleware:Strategies for Building Large, Integrated Systems. 2nd ed. UpperSaddle River, N.J.: Addison-Wesley Professional, 2004.Myerson, Judith M. The Complete Book of Middleware. Boca Raton,Fla.: CRC Press, 2002.Puder, Arno, Kay Römer, and Frank Pilhofer. Distributed SystemsArchitecture: A Middleware Approach. San Francisco: MorganKaufman, 2006.“What Is Middleware?” ObjectWeb. Available online. URL: http://middleware.objectweb.org/. Accessed August 15, 2007.military applications of computersWar has always been one of the most complex of humanenterprises. Even leaving actual combat aside, the U.S. militaryand defense establishment constitute a huge employer,research and training agency, and transportation network.Managing all these activities require sophisticated database,inventory, tracking, and communications systems. Whenthousands of private defense contractors of varying sizesare considered as part of the system, the complexity andscope of the enterprise become even larger.Specifically, military information technology applicationscan be divided into the following broad areas: logistics,training, operations, and battle management.LogisticsIt is often said that colonels worry about tactics while generalspreoccupy themselves largely with logistics. Logisticsis the management of the warehousing, distribution, andtransportation systems that supply military establishmentsand forces in the field with the equipment and fuel theyneed to train and to fight. Logistics within the United Statesis analogous to similar problems for very large corporations.The same bar codes, point of use terminals, and othertracking, inventory, and distribution systems that Amazon.com uses to get books quickly to customers while avoidingexcessive inventory are, in principle, applicable to modernizingmilitary logistic systems.An added dimension emerges when logistical supportmust be supplied to forces operating in remote countries,possibly in the face of efforts by an enemy to disrupt supply.Such considerations as efficient loading procedures toaccommodate limited air transport capacity, prioritizationof shipping to provide the most urgently needed items, andtransportation security can all come into play. (The militaryhas pioneered the use of retinal scanners and other systemsfor controlling access to sensitive areas. See biometrics.)The need for mobility and compactness makes laptopsand even palmtops the form factors of choice. Military or“milspec” versions of computer hardware are generally builtwith more rugged components and greater resistance toheat, moisture, or dust.