symbolijoukko

Symbolijoukko is a term used to refer to a collection of symbols that can be used within a formal system, such as a programming language, a formal grammar, or a mathematical framework. The concept is closely related to the idea of an alphabet in formal language theory. A symbolijoukko may be finite or infinite, though most practical applications use a finite set of symbols.

In formal languages and computing, the symbolijoukko defines the basic building blocks from which strings and tokens are constructed. For example, a decimal digit set {0,1,2,3,4,5,6,7,8,9} or a more extensive operator and punctuation set used by a programming language. In text processing, the broader term merkkijoukko (character set) is often used to describe the symbols that can appear in text; a symbolijoukko can be seen as a specific subset of a character set chosen for a particular formal purpose, such as lexical analysis or grammar design.

A key role of the symbolijoukko in theory is to determine the alphabet over which strings are defined. In automata theory, finite automata and formal grammars operate on strings formed from the symbolijoukko, and the size and composition of the set influence parsing, language recognition, and the design of tokens and operators. Unicode and other comprehensive character sets serve as large-scale symbolijoukko frameworks from which smaller, application-specific sets are derived.

See also: alphabet, formal language, automata theory, character set, token.