| The Evolution of TTCN |
The Evolution of TTCN
Work on Tree and Tabular Combined Notation (TTCN) first started in 1984 in
ISO/IEC JTC 1/ SC 21 and in CCITT SG VII as part of the work on OSI conformance
testing methodology and framework. It was standardized as twin texts ISO/IEC
9646-3 and CCITT Rec. X.292 in 1992 as one of the set of 7 twin texts (ISO/IEC
9646 and CCITT X.290-series) on OSI conformance testing. Since then TTCN was
widely used for describing protocol conformance test suites in standard
organizations such as ITU-T, ISO/IEC, ATM Forum, and ETSI and in industries. The
main characteristics of TTCN that contributed to its wide acceptance are that:
- its Tabular Notation allows its user to describe easily and naturally in
a tree form all possible scenarios of stimulus and various reactions to it
between the tester and the Implementation Under Test (IUT),
- its verdict system is designed such that to facilitate conformance
judgment on the test result agrees against the test purpose, and
- it provides a mechanism to describe appropriate constraints on received
messages so that conformance of the received messages can be mechanically
evaluated against the test purpose.
However, the first edition of TTCN was not suitably designed to describe the
concurrent behavior within the tester or within IUT or between them and the need
for an extension to deal with concurrent behavior efficiently was soon
recognized. In the process of extension, in addition to concurrency mechanism,
the concepts of module and package were newly introduced to TTCN to increase
reusability and to achieve encapsulation. Also manipulation of ASN.1 encoding
was made possible beyond simple syntax declaration. The TTCN extended in this
way was adopted as TTCN version 2 (TTCN-2) in ISO/IEC in 1998 and in ITU-T in
1998.
In spite of the improvements in TTCN-2, TTCN was designed from the beginning
with OSI-based protocol conformance testing in mind and even TTCN-2 was not
adequate for various kinds of testing such as interoperability testing,
robustness testing, regression testing, system testing and integration testing
or for various emerging testing application areas such as mobile protocol,
Internet protocol, service testing, module testing, CORBA-based platform testing
and API testing. Therefore a more flexible and powerful test description
language was called for. In order to meet such a need, the Special Task Force (STF)
133 and 156 of ETSI started working on a new version of TTCN in 1998 and
completed it in October 2000.
TTCN-3 retained the proven features of TTCN-2 but was designed to provide the
new features listed above. A single most visible difference is that the previous
versions adopted as the main description notation the Tabular Notation and its
textual counterpart a machine-processible language for translation to programs
whereas in TTCN-3 the usual programming language-like notation is adopted as the
core language with the Tabular Notation and MSC as presentation languages.
Comparing it with TTCN-2, TTCN-3 has improvements in that TTCN-3 has a
- well-defined syntax, interchange format and static semantics and
- precise execution algorithm (operational semantics).
The major new capabilities of TTCN-3 are:
- different presentation formats (e.g. tabular and MSC presentation
formats),
- dynamic concurrent testing configurations,
- operations for synchronous and asynchronous communications,
- ability to specify encoding information and other attributes (including
user extensibility),
- data and signature templates with powerful matching mechanisms,
- type and value parameterization,
- assignment and handling of test verdicts,
- test suite parameterization and test case selection mechanisms, and
- combined use of TTCN-3 and ASN.1 (and potential use with other languages
such as IDL)..
In October 2000, TTCN-3 was approved in ETSI. Then it was submitted to ITU-T
as Z.140 (series). Z.140 and Z.141 were approved July 2001. Certainly TTCN-3 is
a significant improvement over TTCN-2 in precision, expressiveness and
capability to meet emerging testing needs. However, the industry and standard
organizations put a lot of investment in developing TTCN and TTCN-2 test suites
and would not want the investment to be simply discarded or demoted today when
TTCN-3 does not provide backward compatibility for the preceding versions and
new features require some extent of test-drives. Meanwhile, TTCN-2 can continue
to serve the test specification needs until TTCN-3 makes its way to such needs
and becomes accepted.
References:
TTCN
[1] CCITT Recommendation X.292, OSI conformance testing methodology and
framework for protocol Recommendations for CCITT applications – The Tree and
Tabular Combined Notation (TTCN), 1992
[2] ISO/IEC 9646-3, Information technology – Open systems interconnection
– Conformance testing methodology and framework – Part 3: The Tree and
Tabular Combined Notation (TTCN), 1992
TTCN-2
[1] IUT-T Recommendation X.292, OSI conformance testing methodology and
framework for protocol Recommendations for ITU-T applications – The Tree and
Tabular Combined Notation (TTCN), 1998
[2] ISO/IEC 9646-3, Information technology – Open systems interconnection
– Conformance testing methodology and framework – Part 3: The Tree and
Tabular Combined Notation (TTCN), 1998
TTCN-3
[1] ETSI, "Methods for Testing and Specification (MTS); The Tree and
Tabular Combined Notation version 3; TTCN-3: Core Language", October 2000.
[2] ITU-T Recommendation Z.140, The Tree and Tabular Combined Notation
version 3 (TTCN-3): Core Language, 2001
[3] ITU-T Recommendation Z.141, The Tree and Tabular Combined Notation
version 3 (TTCN-3): Tabular Presentation Format, 2001
Further Information:
TTCN
[1] Anthony Wiles, "The Tree and Tabular Combined Notation – A
Tutorial," http://www.etsi.org/ptcc/ptcc_downloads.htm
- TTCN
TTCN-2
[1] Anthony Wiles, "The Tree and Tabular Combined Notation – A
Tutorial," http://www.etsi.org/ptcc/ptcc_downloads.htm
- TTCN
[2] ETSI, PEX Competence Center, "Tutorial: TTCN Version 2",
Presentation Slides.
TTCN-2++
[1] ETSI, "Information technology – Open Systems Interconnection
Conformance testing methodology and framework; The Tree and Tabular Combined
Notation (TTCN-2++), TR 101 666 V1.0.0, May 1999.
TTCN-3
[1] Jen Grabowski, Dieter Hogrefe, "Towards the Third Edition of TTCN,"
The IFIP 12th International Conference on Testing of Communicating
Systems (TestCom 1999), Budapest, Hungary, 1999.
[2] Jen Grabowski, Anthony Wiles, Colin Willcock, Dieter Hogrefe, "On
the design of the new testing language TTCN-3," The IFIP 13th
International Conference on Testing of Communicating Systems (TestCom 2000),
Ottawa, Canada, 2000.
[3] Anthony Wiles, "TTCN-3: An Introductory Overview," Presentation
Slides, ETSI 2000.
[4] IUT-T SG7 "TD2054: A very short introduction to TTCN-3", Jan
2001.
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