| 词条 | Metavariable |
| 释义 |
In logic, a metavariable (also metalinguistic variable[1] or syntactical variable[2]) 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. John Corcoran considers this terminology unfortunate because it obscures the use of schemata and because such "variables" do not actually range over a domain.[3]{{rp|220|date=November 2012}} 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.[4] Attempts to formalize the notion of metavariable result in some kind of type theory.[5] See also
Notes1. ^{{harvnb|Hunter|page=13}}. 2. ^{{harvnb|Shoenfield|2001|page=7}}. 3. ^{{harvnb|Corcoran|2006|page=220}}. 4. ^{{harvnb|Tennent|2002|pages=36–37, 210}}. 5. ^Masahiko Sato, Takafumi Sakurai, Yukiyoshi Kameyama, and Atsushi Igarashi. "Calculi of Meta-variables{{dead link|date=January 2018 |bot=InternetArchiveBot |fix-attempted=yes }}" 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 References
4 : Metalogic|Variables (mathematics)|Syntax (logic)|Logic symbols |
| 随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。