Editing Vienna Development Method (section)

==History==
The origins of VDM-SL lie in the [[IBM]] Laboratory in [[Vienna]] where the first version of the language was called the '''V'''ienna '''D'''efinition '''L'''anguage (VDL).<ref>Bjørner&Jones 1978, [https://link.springer.com/content/pdf/bfm%3A978-3-540-35836-7%2F1.pdf Introduction], p.ix</ref> The VDL was essentially used for giving [[operational semantics]] descriptions in contrast to the VDM – Meta-IV which provided [[denotational semantics]]<ref>Introductory remarks by Cliff B. Jones (editor) in Bekič 1984, p.vii</ref>
<blockquote>
«Towards the end of 1972 the Vienna group again turned their attention to the problem of systematically developing a compiler from a language definition. The overall approach adopted has been termed the "Vienna Development Method"... The meta-language actually adopted ("Meta-IV") is used to define major portions of PL/1 (as given in ECMA 74 – interestingly a "formal standards document written as an abstract interpreter") in BEKIČ 74.»<ref>Bjørner&Jones 1978, [https://link.springer.com/content/pdf/bfm%3A978-3-540-35836-7%2F1.pdf Introduction], p.xi</ref>
</blockquote>

There is no connection between [[Meta-IV]],<ref>Bjørner&Jones 1978, p.24.</ref> and Schorre's [[META II]] language, or its successor [[Tree Meta]]; these were [[compiler-compiler]] systems rather than being suitable for formal problem descriptions.

So Meta-IV was "used to define major portions of" the [[PL/I]] programming language. Other programming languages retrospectively described, or partially described, using Meta-IV and VDM-SL include the [[BASIC programming language]], [[FORTRAN]], the [[APL programming language]], [[ALGOL]] 60, the [[Ada programming language]] and the [[Pascal programming language]]. Meta-IV evolved into several variants, generally described as the Danish, English and Irish Schools.

The "English School" derived from work by [[Cliff Jones (computer scientist)|Cliff Jones]] on the aspects of VDM not specifically related to language definition and compiler design (Jones 1980, 1990). It stresses modelling persistent<ref>See the article on [[Persistence (computer science)|persistence]] for its use within computer science.</ref> state through the use of data types constructed from a rich collection of base types. Functionality is typically described through operations which may have side-effects on the state and which are mostly specified implicitly using a precondition and postcondition. The "Danish School" ([[Dines Bjørner|Bjørner]] ''et al.'' 1982) has tended to stress a constructive approach with explicit operational specification used to a greater extent. Work in the Danish school led to the first European validated [[Ada programming language|Ada]] compiler.

An [[International Organization for Standardization|ISO]] Standard for the language was released in 1996 (ISO, 1996).