2.1 Natural Languages and Artificial Languages
A natural language is an ordinary hereditary language, spoken by a group of individuals as their native tongue. An example of a natural language is English. Natural languages are mainly studied by linguists, even though philosophers and computer scientists also study language through the philosophy of language and through computational linguistics. The above definition excludes Esperanto from the set of natural languages, as well as all present or future computer languages. These languages are called artificial languages. A subclass of the artificial languages is that of machine languages which as the name implies, are used by a machine to code letters, numbers, instructions, and storage locations in such a way that a computer does not require any translation in order to function according to its coded instructions. Pascal, C++, and Prolog are examples of machine languages. Formal languages are also artificial languages. A formal language, put simply, is a set of symbols that is accompanied by rules for concatenating the symbols into sequences. The special notation used in describing a game of chess is an example of a formal language, as are languages used to calculate in logic or mathematics. In computer science the ability of various formal languages to reflect the subtleties in descriptions of natural language is carefully studied, especially within the fields of conceptual modelling, database theory, and software engineering. Interest here lies mainly in the expressive power of languages. Other factors such as correctness, soundness, and completeness are discussed later in Chapter 4. The ideal language for any one given purpose is the smallest, yet that which allows everything required of it to be expressed with the greatest of ease. With such a language at our disposal the representation of a message could be made more abstract and manageable than would have been possible in the original natural language. Yet this could be achieved without losing content in the process. In Fig: 2-2, a simple classification of languages is presented.
Fig: 2-2 The relation among four different classes of languages, with examples