In logic, syntax is anything having to do with formal languages or formal systems without regard to any interpretation or meaning given to them. Syntax is concerned with the rules used for constructing, or transforming the symbols and words of a language, as contrasted with the semantics of a language which is concerned with its meaning.
The symbols, formulas, systems, theorems and proofs expressed in formal languages are syntactic entities whose properties may be studied without regard to any meaning they may be given, and, in fact, need not be given any.
Syntax is usually associated with the rules (or grammar) governing the composition of texts in a formal language that constitute the well-formed formulas of a formal system.
In computer science, the term syntax refers to the rules governing the composition of well-formed expressions in a programming language. As in mathematical logic, it is independent of semantics and interpretation.
Syntactic entities
Symbols
A symbol is an idea, abstraction or concept, tokens of which may be marks or a metalanguage of marks which form a particular pattern. Symbols of a formal language need not be symbols of anything. For instance there are logical constants which do not refer to any idea, but rather serve as a form of punctuation in the language (e.g. parentheses). A symbol or string of symbols may comprise a well-formed formula if the formulation is consistent with the formation rules of the language. Symbols of a formal language must be capable of being specified without any reference to any interpretation of them.
Formal language
A formal language is a syntactic entity which consists of a set of finite strings of symbols which are its words (usually called its well-formed formulas). Which strings of symbols are words is determined by the creator of the language, usually by specifying a set of formation rules. Such a language can be defined without reference to any meanings of any of its expressions; it can exist before any interpretation is assigned to it – that is, before it has any meaning.
Formation rules
Formation rules are a precise description of which strings of symbols are the well-formed formulas of a formal language. It is synonymous with the set of strings over the alphabet of the formal language which constitute well formed formulas. However, it does not describe their semantics (i.e. what they mean).
Propositions
A proposition is a sentence expressing something true or false. A proposition is identified ontologically as an idea, concept or abstraction whose token instances are patterns of symbols, marks, sounds, or strings of words. Propositions are considered to be syntactic entities and also truthbearers.
Formal theories
A formal theory is a set of sentences in a formal language.
Formal systems
A formal system (also called a logical calculus, or a logical system) consists of a formal language together with a deductive apparatus (also called a deductive system). The deductive apparatus may consist of a set of transformation rules (also called inference rules) or a set of axioms, or have both. A formal system is used to derive one expression from one or more other expressions. Formal systems, like other syntactic entities may be defined without any interpretation given to it (as being, for instance, a system of arithmetic).
Syntactic consequence within a formal system
A formula A is a syntactic consequence within some formal system 
of a set Г of formulas if there is a derivation in formal system of A from the set Г.
Syntactic consequence does not depend on any interpretation of the formal system.
Syntactic completeness of a formal system
A formal system 
is syntactically complete (also deductively complete, maximally complete, negation complete or simply complete) iff for each formula A of the language of the system either A or ¬A is a theorem of . In another sense, a formal system is syntactically complete iff no unprovable axiom can be added to it as an axiom without introducing an inconsistency. Truth-functional propositional logic and first-order predicate logic are semantically complete, but not syntactically complete (for example the propositional logic statement consisting of a single variable "a" is not a theorem, and neither is its negation, but these are not tautologies). Gödel's incompleteness theorem shows that no that is sufficiently powerful, such as the Peano axioms, can be both consistent and complete.
Interpretations
An interpretation of a formal system is the assignment of meanings to the symbols, and truth values to the sentences of a formal system. The study of interpretations is called formal semantics. Giving an interpretation is synonymous with constructing a model. An interpretation is expressed in a metalanguage, which may itself be a formal language, and as such itself is a syntactic entity.
See also
References
- Dictionary Definition
- Hunter, Geoffrey (1996) [1971]. Metalogic: An Introduction to the Metatheory of Standard First-Order Logic. University of California Press (published 1973). p. 7. ISBN 9780520023567. OCLC 36312727. (accessible to patrons with print disabilities)
- Dummett, M. (1981). Frege: Philosophy of Language. Harvard University Press. p. 82. ISBN 9780674319318. Retrieved 2014-10-15.
- Lear, J. (1986). Aristotle and Logical Theory. Cambridge University Press. p. 1. ISBN 9780521311786. Retrieved 2014-10-15.
- Creath, R.; Friedman, M. (2007). The Cambridge Companion to Carnap. Cambridge University Press. p. 189. ISBN 9780521840156. Retrieved 2014-10-15.
- "syntactic consequence from FOLDOC". swif.uniba.it. Archived from the original on 2013-04-03. Retrieved 2014-10-15.
- Hunter, Geoffrey, Metalogic: An Introduction to the Metatheory of Standard First-Order Logic, University of California Press, 1971, p. 75.
- "A Note on Interaction and Incompleteness" (PDF). Retrieved 2014-10-15.
- Wijesekera, Duminda; Ganesh, M.; Srivastava, Jaideep; Nerode, Anil (2001). "Normal forms and syntactic completeness proofs for functional independencies". Theoretical Computer Science. 266 (1–2). portal.acm.org: 365–405. doi:10.1016/S0304-3975(00)00195-X.
- Barwise, J. (1982). Handbook of Mathematical Logic. Elsevier Science. p. 236. ISBN 9780080933641. Retrieved 2014-10-15.
- "syntactic completeness from FOLDOC". swif.uniba.it. Archived from the original on 2001-05-02. Retrieved 2014-10-15.
External links
Media related to Syntax (logic) at Wikimedia Commons
In logic syntax is anything having to do with formal languages or formal systems without regard to any interpretation or meaning given to them Syntax is concerned with the rules used for constructing or transforming the symbols and words of a language as contrasted with the semantics of a language which is concerned with its meaning This diagram shows the syntactic entities which may be constructed from formal languages The symbols and strings of symbols may be broadly divided into nonsense and well formed formulas A formal language is identical to the set of its well formed formulas The set of well formed formulas may be broadly divided into theorems and non theorems The symbols formulas systems theorems and proofs expressed in formal languages are syntactic entities whose properties may be studied without regard to any meaning they may be given and in fact need not be given any Syntax is usually associated with the rules or grammar governing the composition of texts in a formal language that constitute the well formed formulas of a formal system In computer science the term syntax refers to the rules governing the composition of well formed expressions in a programming language As in mathematical logic it is independent of semantics and interpretation Syntactic entitiesSymbols A symbol is an idea abstraction or concept tokens of which may be marks or a metalanguage of marks which form a particular pattern Symbols of a formal language need not be symbols of anything For instance there are logical constants which do not refer to any idea but rather serve as a form of punctuation in the language e g parentheses A symbol or string of symbols may comprise a well formed formula if the formulation is consistent with the formation rules of the language Symbols of a formal language must be capable of being specified without any reference to any interpretation of them Formal language A formal language is a syntactic entity which consists of a set of finite strings of symbols which are its words usually called its well formed formulas Which strings of symbols are words is determined by the creator of the language usually by specifying a set of formation rules Such a language can be defined without reference to any meanings of any of its expressions it can exist before any interpretation is assigned to it that is before it has any meaning Formation rules Formation rules are a precise description of which strings of symbols are the well formed formulas of a formal language It is synonymous with the set of strings over the alphabet of the formal language which constitute well formed formulas However it does not describe their semantics i e what they mean Propositions A proposition is a sentence expressing something true or false A proposition is identified ontologically as an idea concept or abstraction whose token instances are patterns of symbols marks sounds or strings of words Propositions are considered to be syntactic entities and also truthbearers Formal theories A formal theory is a set of sentences in a formal language Formal systems A formal system also called a logical calculus or a logical system consists of a formal language together with a deductive apparatus also called a deductive system The deductive apparatus may consist of a set of transformation rules also called inference rules or a set of axioms or have both A formal system is used to derive one expression from one or more other expressions Formal systems like other syntactic entities may be defined without any interpretation given to it as being for instance a system of arithmetic Syntactic consequence within a formal system A formula A is a syntactic consequence within some formal system FS displaystyle mathcal FS of a set G of formulas if there is a derivation in formal system FS displaystyle mathcal FS of A from the set G G FSA displaystyle Gamma vdash mathrm F S A Syntactic consequence does not depend on any interpretation of the formal system Syntactic completeness of a formal system A formal system S displaystyle mathcal S is syntactically complete also deductively complete maximally complete negation complete or simply complete iff for each formula A of the language of the system either A or A is a theorem of S displaystyle mathcal S In another sense a formal system is syntactically complete iff no unprovable axiom can be added to it as an axiom without introducing an inconsistency Truth functional propositional logic and first order predicate logic are semantically complete but not syntactically complete for example the propositional logic statement consisting of a single variable a is not a theorem and neither is its negation but these are not tautologies Godel s incompleteness theorem shows that no that is sufficiently powerful such as the Peano axioms can be both consistent and complete Interpretations An interpretation of a formal system is the assignment of meanings to the symbols and truth values to the sentences of a formal system The study of interpretations is called formal semantics Giving an interpretation is synonymous with constructing a model An interpretation is expressed in a metalanguage which may itself be a formal language and as such itself is a syntactic entity See alsoSymbol formal Formation rule Formal grammar Syntax linguistics Syntax programming languages Mathematical logic Well formed formulaReferencesDictionary Definition Hunter Geoffrey 1996 1971 Metalogic An Introduction to the Metatheory of Standard First Order Logic University of California Press published 1973 p 7 ISBN 9780520023567 OCLC 36312727 accessible to patrons with print disabilities Dummett M 1981 Frege Philosophy of Language Harvard University Press p 82 ISBN 9780674319318 Retrieved 2014 10 15 Lear J 1986 Aristotle and Logical Theory Cambridge University Press p 1 ISBN 9780521311786 Retrieved 2014 10 15 Creath R Friedman M 2007 The Cambridge Companion to Carnap Cambridge University Press p 189 ISBN 9780521840156 Retrieved 2014 10 15 syntactic consequence from FOLDOC swif uniba it Archived from the original on 2013 04 03 Retrieved 2014 10 15 Hunter Geoffrey Metalogic An Introduction to the Metatheory of Standard First Order Logic University of California Press 1971 p 75 A Note on Interaction and Incompleteness PDF Retrieved 2014 10 15 Wijesekera Duminda Ganesh M Srivastava Jaideep Nerode Anil 2001 Normal forms and syntactic completeness proofs for functional independencies Theoretical Computer Science 266 1 2 portal acm org 365 405 doi 10 1016 S0304 3975 00 00195 X Barwise J 1982 Handbook of Mathematical Logic Elsevier Science p 236 ISBN 9780080933641 Retrieved 2014 10 15 syntactic completeness from FOLDOC swif uniba it Archived from the original on 2001 05 02 Retrieved 2014 10 15 External linksMedia related to Syntax logic at Wikimedia Commons
