Summary

Scope-objective

This Recommendation defines SDL (Specification and Description Language) intended for unambiguous specification and description of telecommunication systems. The scope of SDL is elaborated in clause 1. This Recommendation is a reference manual for the language.

Coverage

SDL has concepts for behaviour, data description and (particularly for larger systems) structuring. The basis of behaviour description is extended finite state machines communicating by messages. Data description is based on data types for values and objects. The basis for structuring is hierarchical decomposition and type hierarchies. These foundations of SDL are elaborated in the respective main clauses of this Recommendation. A distinctive feature of SDL is the graphical representation.

Applications

SDL is applicable within standard bodies and industry. The main applications areas for which SDL has been designed are stated in 1.2, but SDL is generally suitable for describing reactive systems. The range of application is from requirement description to implementation.

Status/Stability

This Recommendation is the complete language reference manual supported by guidelines for its usage in Supplement 1. Annex F gives a formal definition of SDL semantics. The main text of this Recommendation is stable and needs to be issued immediately to meet market needs, but further study is required to complete Annex F. Appendix I records the status of ITU-T Rec.Z.100, and should be updated as further studies are completed. Although further language extensions are anticipated in the future, SDL‑2000 as defined in this Recommendation should meet most user needs for some years. The current version is based on wide user experience of SDL and recent additional user needs.

The main text is accompanied by annexes:

-           Annex A                                 Index of non-terminals

-           Annex B                                  Reserved for future use (Annex B (03/93) is no longer valid)

-           Annex C                                 Reserved for future use (Annex C (03/93) is no longer in force)

-           Annex D                                 SDL predefined data

-           Annex E                                  Reserved for examples

-           Annex F                                  SDL Formal Definition (published separately)

-           Appendix I                  Status of ITU-T Rec. Z.100, related documents and Recommendations

-           Appendix II                 Guidelines for the maintenance of SDL

-           Appendix III               Systematic conversion of SDL-92 to SDL-2000

ITU-T Rec. Z.100 has also an independently published supplement:

-           Z.100 Supplement 1    SDL+ methodology: use of MSC and SDL (with ASN.1)

Associated work

One method for SDL usage within standards is described in ITU-T Rec. Q.65. A recommended strategy for introducing a formal description technique like SDL in standards is available in ITU-T Rec. Z.110. For references to additional material on SDL, and information on industrial usage of SDL, see http://www.sdl-forum.org.

Background

Different versions of SDL have been recommended by CCITT and ITU-T since 1976. This version is a revision of ITU-T Rec. Z.100 (03/93) and incorporates Addendum 1 to ITU-T Rec. Z.100 (10/96) and parts of ITU-T Rec. Z.105 (03/95). This version is a technical update of ITU-T Rec. Z.100 (11/99) that incorporates a number of technical corrections and amendments, and without the textual phrase alternative syntax, which has been moved to ITU-T Rec. Z.106 (2002).

Compared to SDL as defined in 1992, the version defined in ITU-T Rec. Z.100 (11/99) and in this version has been extended in the areas of object-oriented data, harmonization of a number of features to make the language simpler, and features to enhance the usability of SDL with other languages such as ASN.1, ITU-T ODL (ITU-T Rec. Z.130), CORBA and UML. Other minor modifications have been included. Though care has been taken not to invalidate existing SDL documents, some changes may require some descriptions to be updated to use this version. Details on the changes introduced can be found in 1.5.