In logic, a metavariable (also metalinguistic variable or syntactical variable) is a symbol or symbol string which belongs to a metalanguage and stands for elements of some object language. For instance, in the sentence
- Let A and B be two sentences of a language ℒ
the symbols A and B are part of the metalanguage in which the statement about the object language ℒ is formulated.
The convention is that a metavariable is to be uniformly substituted with the same instance in all its appearances in a given schema. This is in contrast with nonterminal symbols in formal grammars where the nonterminals on the right of a production can be substituted by different instances.
Attempts to formalize the notion of metavariable result in some kind of type theory.
- Hunter, p. 13.
- Shoenfield 2001, p. 7.
- Corcoran 2006, p. 220.
- Tennent 2002, pp. 36–37, 210.
- Masahiko Sato, Takafumi Sakurai, Yukiyoshi Kameyama, and Atsushi Igarashi. "Calculi of Meta-variables" in Computer Science Logic. 17th International Workshop CSL 2003. 12th Annual Conference of the EACSL. 8th Kurt Gödel Colloquium, KGC 2003, Vienna, Austria, August 25-30, 2003. Proceedings, Springer Lecture Notes in Computer Science 2803. ISBN 3-540-40801-0. pp. 484–497
- Corcoran, J. (2006). "Schemata: the Concept of Schema in the History of Logic" (PDF). Bulletin of Symbolic Logic. 12: 219–240.
- Hunter, Geoffrey. Metalogic: An Introduction to the Metatheory of Standard First-Order Logic.
- Shoenfield, Joseph R. (2001) . Mathematical Logic (2nd ed.). A K Peters. ISBN 978-1-56881-135-2.
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