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Question 12/17

Formal languages for telecommunication software and testing

(Continuation of Q12/17)


This Question supports the continued development of a variety of formal languages that are in wide-spread use in telecommunications system design and testing.
This Question covers definition and use of formal ITU system design languages to define the requirements, architecture, and behaviour of telecommunications systems: requirements languages, data description, behaviour specification, testing, and implementation languages. The formal languages for these areas of engineering are widely used in industry and ITU-T and commercial tools support them. The languages can be applied collectively or individually for specification of standards and the realization of products. The ITU system design languages of concern are:
• The User Requirements Notation is applied for the analysis of goals and the definition of use cases, particularly at the initial stages of design.
• Abstract Syntax Notation One (ASN.1) that has proved to be the notation-of-choice for many standardization groups for specification of information passed between entities, and with the associated encoding rules ensure the information can be passed unambiguously, securely and efficiently.
• The Specification and Description Language that allows the stimulus and response behaviour of entities to be specified, and can be combined with the specification of data units in ASN.1.
• A UML profile for the Specification and Description Language, that constrains UML models to a well-defined behaviour that avoids semantic variations inherent in the OMG standard and parts of UML not needed for behaviour covered by the Specification and Description Language.
• Message Sequence Chart notation that allows the sequence of messages between entities can be described, which can also be used to trace the way a system behaves.
• The Testing and Test Control Notation version 3 (TTCN-3) that allows tests for functionality and interoperability of systems to be specified and generic test suites to be written. TTCN-3 is being used in testing ITU-T Recommendations developed by the relevant ITU-T SGs and especially SG11, as the lead group on test specifications, conformance and interoperability testing. ITU-T is producing a large number of Recommendations. To achieve interoperability, it is essential that implementations of these Recommendations conform to the Recommendations.
• CHILL - The ITU-T Programming Language – that has been used widely in the past, though in recent years alternative approaches have been used such as generating code from the Specification and Description Language.
All these ITU system design languages are defined by Recommendations within the scope of this Question, except ASN.1 (and its associated encoding rules).
As well as defining the languages, the documents within the scope of this Question provide guidance on the definition, use and application of the languages (including to some extent ASN.1) for other study groups, external standards development organizations and countries. Recommendations ITU-T Z.110, Z.450, Z.500 and Z.Sup1 give guidance on use and application of the languages. Recommendations ITU-T Z.111 and Z.119 provide guidelines on how any new language Recommendation should be written and are used as included references in other Recommendations (in particular the Z.100 series and Z.150 series).
Recommendations, Supplements and Implementers Guides under responsibility of this Question as of 23 March 2016: X.292, Z.100, Z.101, Z.102, Z.103, Z.104, Z.105, Z.106, Z.107, Z.109, Z.110, Z.111, Z.119, Z.120, Z.121, Z.150, Z.151, Z.161, Z.161.1, Z.161.2, Z.161.3, Z.161.4, Z.161.5, Z.162, Z.163, Z.164, Z.165, Z.165.1, Z.166, Z.167, Z.168, Z.169, Z.170, Z.200, Z.450, Z.500, Z.Sup1, and Z.Imp100.
Texts under development: none.


Study items to be considered include, but are not limited to:
a) What maintenance of definitions of existing ITU system design languages (except ASN.1) adapted to further contemporary user requirements and emerging new architectures and frameworks are needed?
b) What new languages are needed for further contemporary user requirements and emerging new architectures and frameworks (such as the Internet of Things) taking into account Recommendation ITU-T Z.110?


Tasks include, but are not limited to:
a) Maintain Recommendations under responsibility of this Question;
b) Provide general advice to users of the language(s), methodology(y/ies), framework(s) for the language(s) covered by the Question study;
c) Promote the use of the methodologies, frameworks and languages covered by the Question study within other study groups and external SDOs.


• X.680/X.690 series.
• Q11/17, all ITU-T Questions using system design languages.
Study Groups:
• SG11, the Lead Study Group on test specifications, conformance and interoperability testing, all study groups that use the ITU system design languages (SGs 2, 11, 13, 16 and 20 in particular) or specify tests (SGs 2, 9, 11, 13, 15, 16 and 20 in particular), TSAG.
Other ITU-T groups:
Standardization bodies:
• European Telecommunications Standards Institute (ETSI) (TC MTS); Internet Engineering Task Force (IETF); ISO/IEC JTC 1 and its sub-committees that use the ITU system design languages.
Other bodies:
• Object Management Group (OMG); SDL Forum Society.​