Relational Databases and Distributed Systems

Logical Collection of Related Data DatabaseA database is a logically organised collection of related data, generally accessed by a set of programs known as a Database Management System (DBMS), which oversees the creation and use of the database and controls access to the data. The organisation of a database obviates the need to duplicate information to meet the various requirements of different groups of users, and ensures that the data always remains consistent. A large database requires extensive storage facilities. In some organisations and services, databases can be accessed over networks from microcomputers or as videotex. 'Relational' databases and hypertext techniques include extensive and complex cross-reference facilities so that information on related items may be retrieved. Many database programs have been designed to run on micro-computers. Some of these contain computer languages that enable users to change the operation of the database to suit their requirements. For example, a mailing list on a micro-computer constitutes a simple database in which--if the information were available in a structured format--the DBMS could be instructed to print out the addresses of all the people called Smith, or of everyone on the mailing list living in Melbourne, Australia.DataData (computing) is the information that has been prepared, often in a particular format, for a specific purpose. In computing, the term data is used for material distinct from instructions: for example, if a computer multiplies two numbers together, the numbers themselves are the data, operated on by an instruction (to multiply them together). In a more restricted sense, data may be the information input for a particular program, as opposed to the results or output. A third meaning uses data as a term for information not in the form of words, sounds, or images: such data is usually information that is stored in a highly organized and compact form suitable for data processing.Analogue computerAn analogue computer is a computer that uses continuously variable (analogue) quantities to represent numbers. A voltage between 0 and 1 volt might represent numbers between 0.0 and 100.0, for example. Analogue computers can perform complex arithmetical operations extremely quickly with very few components, but they are not very accurate. Digital computers Digital computers have replaced them almost entirely except in signal processing, where the basic analogue computing elements are still used very widely. Recent work suggests that analogue computing techniques might have a significant future in neural network computers. Neural networkThe neural network is a densely interconnected network of simple computer processing units (neurons) imitating some qualities of the biological nervous system. Unlike traditional computers, neural networks share out the computation simultaneously between many processors (parallel processing), enormously increasing their collective power. Consequently, neural networks are well-suited to the computationally intensive tasks of artificial intelligence, for example automatic speech recognition and image processing. The behaviour of a neural network is determined by the strength of its interconnections (synapses); large numbers of synapses help the network to recognize patterns in the presence of noise, and enable it to keep working after some of its synapses have been removed. HypertextHypertext is a generic term for computer systems used to store, retrieve, and view multi-dimensional documents. Hypertext systems are more flexible than conventional databases. Links may be made between parts of a hypertext document so that it can be read in a non-standard order, when pursuing a particular topic. Viewed text may be selected by using a mouse or keyboard, and displayed in a window. The first practical hypertext systems were developed in the 1980s...