telecommunication

Communication between parties at a distance from one another. Modern telecommunication systems—capable of transmitting telephone, fax, data, radio, or television signals—can transmit large volumes of information over long distances. Digital transmission is employed in order to achieve high reliability with minimal noise, or interference, and because it can transmit any signal type, digital or analog. For digital transmission, analog signals must be subjected to a process of analog-to-digital conversion; most television, radio, and voice communications are analog and must be digitized before transmission. Transmission may occur over cables, wireless radio relay systems, or via satellite links.

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United Nations agency headquartered in Geneva. Its roots can be traced to 1865, when the International Telegraph Union was established to coordinate international development of the telegraph. It acquired its present name in 1934 and became a UN specialized agency in 1947. Its activities include regulating allocation of radio frequencies, setting standards on technical and operational matters, and assisting countries in developing their own telecommunications systems.

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Technique of using knowledge from various branches of engineering and science to introduce technological innovations into the planning and development stages of a system. Systems engineering was first applied to the organization of commercial telephone systems in the 1920s and '30s. Many systems-engineering techniques were developed during World War II in an effort to deploy military equipment more efficiently. Postwar growth in the field was spurred by advances in electronic systems and by the development of computers and information theory. Systems engineering usually involves incorporating new technology into complex, man-made systems, in which a change in one part affects many others. One tool used by systems engineers is the flowchart, which shows the system in graphic form, with geometric figures representing various subsystems and arrows representing their interactions. Other tools include mathematical models, probability theory, statistical analysis, and computer simulations.

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Q-Systems are a method of directed graph transformations according to given grammar rules, developed at the Université de Montréal by Alain Colmerauer in the late 1960's for use in natural language processing. The Université de Montréal's machine translation system, TAUM-73, used the Q-Systems as its language formalism.

Each Q-System consists of a set of rewriting rules, which apply to the sentence, which is represented by a directed acyclic graph, using one-way unification. The output of the analysis is again a directed graph (usually containing only one edge); this allows several Q-Systems to be chained, each of them performing a specialized task, together forming a complex system. For example, TAUM 73 consisted of fifteen chained Q-Systems.

Further refinement of the ideas in Q-Systems led to Prolog, designed by Colmerauer along with Robert Kowalski in the 1970's.

References

• Colmerauer, A: Les systèmes Q ou un formalisme pour analyser et synthétiser des phrases sur ordinateur. Mimeo, Montréal, 1969.

External links

• The birth of Prolog (PDF) — describes the Q-systems in Part II