Editing Formal methods (section)

===Specification===
{{Main|Formal specification}}
Formal methods may be used to give a formal description of the system to be developed, at whatever level of detail desired. Further formal methods may depend on this specification to synthesize a program or to verify the correctness of a system. 

Alternatively, specification may be the only stage in which formal methods is used. By writing a specification, ambiguities in the informal requirements can be discovered and resolved. Additionally, engineers can use a formal specification as a reference to guide their development processes.<ref>{{cite journal|last1=Utting|first1=Mark|last2=Reeves|first2=Steve|date=August 31, 2001|title=Teaching formal methods lite via testing|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/stvr.223|journal=Software Testing, Verification and Reliability|volume=11|issue=3|pages=181–195 |doi=10.1002/stvr.223}}</ref>

The need for formal specification systems has been noted for years. In the [[ALGOL 58]] report,<ref>{{cite conference | first = J.W. | last = Backus | title = The Syntax and Semantics of the Proposed International Algebraic Language of Zürich ACM-GAMM Conference | book-title = Proceedings of the International Conference on Information Processing | publisher = UNESCO | year = 1959 }}</ref> [[John Backus]] presented a formal notation for describing [[Syntax (programming languages)|programming language syntax]], later named [[Backus normal form]] then renamed [[Backus–Naur form]] (BNF).<ref>[[Donald Knuth|Knuth, Donald E.]] (1964), Backus Normal Form vs Backus Naur Form. ''[[Communications of the ACM]]'', 7(12):735–736.</ref> Backus also wrote that a formal description of the meaning of syntactically valid ALGOL programs was not completed in time for inclusion in the report, stating that it "will be included in a subsequent paper." However, no paper describing the formal semantics was ever released.<ref>{{cite book|last1=O'Hearn|first1=Peter W.|last2=Tennent|first2=Robert D.|title=Algol-like Languages|date=1997}}</ref>