The Z notation (universally pronounced zed) is a formal specification language used for describing and modelling computing systems. It is targeted at the clean specification of computer programs and the formulation of proofs about program behavior.

Z was developed by the Programming Research Group at Oxford University in the late 1970s and is based on the standard mathematical notation used in axiomatic set theory, lambda calculus, and first-order predicate logic. All expressions in Z notation are typed, thereby avoiding some of the paradoxes of naïve set theory. Z contains a standardized catalog (called the mathematical toolkit) of commonly used mathematical functions and predicates.

Although Z notation uses many non-ASCII symbols, the specification includes suggestions for rendering the Z notation symbols in ASCII and in LaTeX.

Standards

The ISO completed a Z standardization effort in 2002. This standard, entitled Information Technology - Z Formal Specification Notation - Syntax, Type System and Semantics, ISO/IEC 13568:2002, can be obtained directly from ISO.

13568_2002.zip, 1 MB PDF, 196 pages

See also

• Z++
• Formal methods

External links

• Jonathan Bowen's The Z notation
• Specification proposals by Ian Toyn
• Suppliers of the ISO formal specification
• Community Z Tools Project (CZT)