ITU-T Z.101 PDF

Scope and objective

This Recommendation defines the basic features of the Specification and Description Language. The language defined in this document covers the essential features of the language, which is further defined in other Recommendations in the ITU-T Z.100 series. Together with Recommendations [ITU-T Z.100], [ITU-T Z.102], [ITU-T Z.103], [ITU-T Z.104], [ITU-T Z.105], [ITU-T Z.106] and [ITU-T Z.107], this Recommendation forms a reference manual for the language.

Objective

The objective of this Recommendation is to define the basic features of the Specification and Description Language in a canonical concrete syntax. The language defined in this Recommendation is a strict subset of SDL-2010.

The main features not included in this Recommendation are macros, specialization, context parameters, remote procedures and remote variables, state aggregation, priority input, enabling conditions, spontaneous transitions, exceptions, compound statements (other than as task bodies), object data types, synonyms and generic system definition. Where there is choice of syntax for the same abstract grammar the graphical syntax has been chosen, so that, for example, procedure diagram is used rather than procedure definition.

A specification in SDL-2010 starts with an instantiation of a system type. For that reason, Basic SDL-2010 does not include a system diagram. In Comprehensive SDL-2010 such a diagram is considered shorthand for the instantiation of a system type. Similarly, block diagrams and process diagrams are not included, only diagrams for agent types and other types such as composite state and procedure.

The canonical syntax is chosen to be the syntax supported by most tools in the cases where that is simply an alternative to the syntax introduced in SDL-2000 (for example, the use of the keyword returns rather than <result sign>).

Application

This Recommendation is part of the reference manual for the Specification and Description Language. The part of the language defined by this Recommendation does not usually include shorthand notation or Model clauses, so that a model written using only this part of SDL-2010 is not as concise or as readable as one using the full language. The part of the language defined in this Recommendation is mainly applicable if a model is required that is limited in the language features it uses, and it is intended that the model is presented in a concrete form that closely matches the abstract syntax.

In some cases, a Model clause or shorthand has been included, because this was considered the most practical way to describe a feature. One example is the Model clause for expression that explains how the concrete infix syntax maps to operation application.