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Question N/17 - Specification and Implementation Languages
(continuation of Questions 13/17, 24/17, 25/17 and part of Question 14/17 studied during 2001-2004)

1. Motivation

The Specification and Implementation Languages for which the Question is responsible are:
  • Specification and Description Language – SDL (Z.100 series Recommendations);
  • Extended Object Definition Language – eODL (Z.130 series Recommendations);
  • CHILL (Z.200).
The language SDL has become a mature language that is in use, both in industry for system development, as well as within ITU-T itself. The language is being widely used and there is good tool support for the language, and use has been extended to SDL becoming increasingly also an implementation language.

In addition eODL was defined for a technology-independent development of software components. For an early description of their behaviour eODL is combined with SDL by language mapping. Furthermore other language mappings should allow technology-depended transfers to the component implementations in other languages and their deployment. Preposition of all theses mappings is a modelling of distributed systems in eODL described from a perspective of different but related views: computational, implementation, deployment, and target environment view. The development of tools is on the way.

Furthermore, when an interface or protocol is designed which carries data using ASN.1, there are encoding rules that can be used to determine exactly how the information is encoded. However, when Specification and Implementation Languages are used with ASN.1, there is no specific mechanism to establish what encoding rules are used for information on interfaces, or where the ASN.1 encoding rules may (or may not apply).

Developments in the Object Management Group (OMG) language UML have led to a closer alignment of UML and SDL, with SDL primarily targeting the real-time communication systems with high emphasis on formality and capabilities for validation.

The set of relevant Recommendations for this Question are SDL (Z.100), use of data and ASN.1 with SDL (proposed Z.104, Z.105, and Z.107), Interchange Formats (Z.106), joint use of SDL and UML (Z.109), and eODL (Z.130). These Recommendations need to be adapted and maintained, and possibly new ones identified, to meet the needs of users in ITU and industry, and to the development of languages elsewhere, such as at OMG. This Question also includes any issues regarding CHILL (Z.200), though CHILL is no longer considered appropriate for further study.

The development of Specification and Implementation Languages are market-driven. The needs for the language developments come from users, equipment manufacturers, operating organizations, ITU, and other standards bodies (in particular ETSI). Some of these needs are identified directly and some come through tool suppliers who are subject to market pressure.

The collaboration between experts from ITU-T and the SDL Forum Society needs to continue and strengthen the very effective practice established in prior study periods.

2. Question

What new Recommendations and changes to existing Recommendations, or other provisions are required to:

a) Ensure the release of Specification and Implementation Languages that are adapted to further contemporary user requirements;

b) Support the use of Specification and Implementation Languages in emerging new architectures and frameworks;

c) Establish a coherent set of Specification and Implementation Languages supporting development from high-level design to implementation to execution and deployment;

d) Support of new versions of related languages such as ASN.1 and IDL;

e) Enable improved joint use of UML with ITU-T Specification and Implementation Languages;

f) Support the computational modelling of a new generation of telecommunication systems;

g) Enable computational objects to be configured statically; and

h) Allow different natural languages and systems of writing to be used with Specification and Implementation Languages to aid human understanding? (for example, the use of Hindi in eODL diagrams).

3. Tasks

a) Maintain a master list of corrections of the current version of all Recommendations under maintenance.

b) Maintain the formal basis for SDL Recommendations, thereby placing emphasis on ease of use and easy maintainability, and continue to maintain the formal basis.

c) Continue study of new uses of Specification and Implementation Languages.

d) Issue new versions of Z.10x and Z.13x Recommendations as and when needed. It is envisaged that updates will be produced and published as Study Group reports or addenda to Z.10x and Z.13x Recommendations, and these changes consolidated into these Recommendations. The direction of the effort should be towards relative stability of the languages but with improved usability: both as languages on their own and in combination with each other.

e) Assist in the development of UML profiles for ITU-T Specification and Implementation Languages (Z.109 and the proposed Z.139) under Question P/17 on System design Languages Framework and Unified Modelling Language.

4. Relationships

Recommendations: X.68x, X.69x, Z.12x, Z.15x, X.901, X.902, X.903, X.920, X.931, Z.600

Questions: M/17, O/17, P/17, Q/17 and R/17

Study Groups: All Study Groups that use ITU-T Specification and Implementation Languages, in particular, support of the use of SDL for methodology and signalling specifications in ITU-T SG 11.

Standardization bodies: ETSI (TC MTS); OMG

Other bodies SDL Forum Society, representing the users of SDL


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