Editing Specification language (section)

==Overview==
Specification languages are generally not directly executed. They are meant to describe the ''what'', not the ''how''. It is considered an error if a requirement specification is cluttered with unnecessary implementation detail.

A common fundamental assumption of many specification approaches is that programs are modelled as [[algebra]]ic or [[model theory|model-theoretic]] structures that include a collection of [[set (mathematics)|sets]] of data values together with [[function (mathematics)|functions]] over those sets.  This level of abstraction coincides with the view that the correctness of the input/output behaviour of a program takes precedence over all its other properties.

In the ''property-oriented'' approach to specification (taken e.g. by [[Common Algebraic Specification Language|CASL]]), specifications of programs consist mainly of logical [[axiom]]s, usually in a [[logical system]] in which equality has a prominent role, describing the properties that the functions are required to satisfy—often just by their interrelationship.
This is in contrast to so-called [[model-based specification|model-oriented specification]] in frameworks like [[Vienna Development Method|VDM]] and [[Z notation|Z]], which consist of a simple realization of the required behaviour.

Specifications must be subject to a process of ''refinement'' (the filling-in of implementation detail) before they can actually be implemented. The result of such a refinement process is an executable algorithm, which is either formulated in a programming language, or in an executable subset of the specification language at hand. For example, [[Hartmann pipeline]]s, when properly applied, may be considered a [[dataflow]] specification which ''is'' directly executable.  Another example is the [[actor model]] which has no specific application content and must be ''specialized'' to be executable.

An important use of specification languages is enabling the creation of [[Mathematical proof|proof]]s of [[program correctness]] (''see [[Automated theorem prover|theorem prover]]'').