The purpose of recommending SDL (Specification and Description Language) is to provide a language for
unambiguous specification and description of the behaviour of telecommunication systems. The specifications and
descriptions using SDL are intended to be formal in the sense that it is possible to analyse and interpret them
unambiguously.
The terms specification and description are used with the following meaning:
a) a specification of a system is the description of its required behaviour; and
b) a description of a system is the description of its actual behaviour; that is, its implementation.
A system specification, in a broad sense, is the specification of both the behaviour and a set of general parameters of the
system. However, SDL is intended to specify the behavioural aspects of a system; the general parameters describing
properties like capacity and weight have to be described using different techniques.
NOTE ? Since there is no distinction between use of SDL for specification and its use for description, the term specification is used
in this Recommendation for both required behaviour and actual behaviour.
The general objectives when defining SDL have been to provide a language that:
a) is easy to learn, use and interpret;
b) provides unambiguous specification for ordering, tendering and design, while also allowing some issues to be
left open;
c) may be extended to cover new developments;
d) is able to support several methodologies of system specification and design.
ITU-T Z.100-2007 history
2007ITU-T Z.100-2007 Specification and Description Language (SDL) Study Group 17