1、STD-ITU-T RECMN SERIES A SUPP 1-ENGL 1778 qb2571 Ob54070 717 INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Series A Supplement I (09198) SERIES A: ORGANIZATION OF THE WORK OF THE ITU-T Guidelines on quality aspects of protocol related Recommendations Sup
2、plement I to ITU-T A-series Recommendations (Previously CCITT Recommendations) - - STD-ITU-T RECMN SERIES A SUPP 1-ENGL 1778 48b2571 Ob54071 b55 ITU-T A-SERIES RECOMMENDATIONS ORGANIZATION OF THE WORK OF THE ITU-T For further details, please refer to ITU-T List of Recommendations. SUPPLEMENT 1 TO IT
3、U-T A-SERIES RECOMMENDATIONS GUIDELINES ON QUALITY ASPECTS OF PROTOCOL RELATED RECOMMENDATIONS Summary This Supplement provides guidelines on the quality aspects of protocol related ITU-T Recommendation with the objective of: 1) improving the quality of protocol related Recommendations; and 2) helpi
4、ng to improve the interoperability of products based on these Recommendations. In order to encourage the widest possible use of ITU-T Protocol Related Recommendations, it is important that these Recommendations are of the highest possible quality. Several aspects of Quality that play an important ro
5、le for users of these ITU-T Recommendations have been selected for this purpose. These are: readability, completeness, correctness, consistency, unambiguity, implementability and testability. Annex A of this Supplement contains a quality check-list to assist the developers of protocol related Recomm
6、endations in determining which sections of the Quality Guidelines have been addressed. Source Supplement 1 to ITU-T A-series Recommendations was prepared by ITU-T TSAG (1997-2000) and was approved under the WTSC Resolution No. 5 procedure on the 1 lth of September 1998. I STD.ITU-T RECMN SERIES A SU
7、PP 1-ENGL 1798 = 48b257L Ob54093 428 FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying techn
8、ical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which
9、, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a co
10、llaborative basis with IS0 and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that the practice or
11、 implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation developme
12、nt process. As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are theref
13、ore strongly urged to consult the TSB patent database. O ITU 1998 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. 11 A series - Supp
14、lement 1 (09/98) CONTENTS 1 2 3 4 5 6 7 7.1 7.2 7.3 7.4 8 9 9.1 9.2 9.3 9.4 9.5 9.6 9.7 10 10.1 10.2 10.3 Scope Purpose . Objective . Field of application . Definitions Acronyms . Developing high quality Recommendations Overview of the quality aspects Upfront identification . Formal Description Tech
15、niques . Overview of the process . Quality checks Specific guidelines Readability Completeness of Recommendations . 9.2.1 Conformance section . 9.2.2 Tools for completeness checking 9.2.3 Testing methodology . 9.3.1 Validation of specifications . 9.3.3 Publication phase . 9.3.4 Maintenance Consisten
16、cy . Unambiguity . Implementability . Correctness . 9.3.2 Abstract Test Suite (ATS) . 9.6.1 Reduction of the number of options 9.6.2 Best technical solutions . Testability . Use of tools in developing Recommendations . Timely Recommendations Early error detection . Lower cost A series . Supplement 1
17、 (09/98) 1 1 1 1 1 2 4 4 4 5 5 5 5 5 5 6 6 6 6 6 7 7 7 7 . 111 Page 11 References 7 Annex A - Quality Check-list for Protocol Related Recommendations . 8 A. 1 General Check-list 8 A.2 Specific Check-list 8 iv A series - Supplement 1 (09/98) Introduction In order to encourage the widest possible use
18、of ITU-T Protocol Related Recommendations, it is important that these Recommendations are of the highest possible quality. Several aspects of Quality that play an important role for users of these ITU-T Recommendations have been selected for this purpose. They are: readability, completeness, correct
19、ness, consistency, unambiguity, implementability and testability. A series - Supplement 1 (09/98) V Supplement 1 to A-series Recommendations GUIDELINES ON QUALITY ASPECTS OF PROTOCOL RELATED RECOMMENDATIONS (Geneva, 1998) 1 Scope This Supplement covers the readability, correctness, completeness, con
20、sistency, unambiguity, implementability and testability aspects of quality of Protocol Related Recommendations and specifies a process which can assist in the development of higher quality Recommendations. 2 Purpose The purpose of the quality guidelines is to serve as a reference to ensure a consist
21、ent, high quality standard of Protocol Related Recommendations and the same level of understanding of this subject by all Study Groups. 3 Objective The main objective of this supplement is to improve the quality of ITU-T Protocol Related Recommendations and help to improve the interoperability of pr
22、oducts which are based on these ITU-T Recommendations. 4 Field of application The criteria and the process apply primarily to new Protocol Related Recommendations under development, but may be applied to the evaluation of the quality of the existing protocol related Recommendations. The quality aspe
23、cts should be applied by the relevant Study Groups beginning with the planning phase and continuing through all subsequent phases leading to approval of the Recommendation, and in some cases, through the implementation phase. 5 Definitions This supplement defines the following terms. 5.1 formal desc
24、ription technique (FDT): Standardized languages e.g. SDL, MSC and ASN. 1 , and other techniques, e.g. GDMO, intended for formal specification of system behaviour, structure and data. 5.2 Specification and description language (SDL): Internationally standardized formal language for speciQing and desc
25、ribing real-time systems. 5.3 message sequence charts (MSC): Internationally standardized language for describing sequences of messages interchanged between system components and their environment, 5.4 abstract test suite (ATS): A test suite composed of abstract test cases. A series - Supplement 1 (
26、09198) 1 5.5 abstract test case: A complete and independent specification of the actions required to achieve a specific test purpose, defined at the level of abstraction of a particular Abstract Test Method, starting in a stable testing state and ending in a stable testing state. 5.6 abstract test m
27、ethod: The description of how an Implementation Under Test is to be tested, given an appropriate level of abstraction to make the description independent of any particular realization of a Means of Testing, but with enough detail to enable abstract test cases to be specified for this test method. 5.
28、7 executable test suite (ETS): A test suite composed of executable test cases. 5.8 executable test case: A realization of an abstract test case. 5.9 tree and tabular combined notation (TTCN): A standardized notation for speciing conformance test suites in a manner that is independent of test methods
29、, layered software architectures or protocols and which reflects the abstract testing methodology defined in Recommendations X.290 and X.291. 5.10 validation: A process of checking a specification to ensure that it is syntactically and semantically correct and represents the intended behaviour. 5.11
30、 conformance clause: A part of a standard or Recommendation which identifies what in the standard or Recommendation should be met in order to conform to the standard or Recommendation. 5.12 specification: Prescription of the design of an aspect of a product or a set of products. 5.13 implementation
31、conformance statement (ICs): A statement made by the supplier of an implementation or system claimed to conform to a given specification, stating which capabilities have been implemented. The ICs can take several forms: protocol ICs, profile ICs, profile specific ICs, managed object ICs and informat
32、ion object ICs. 5.14 implementation extra information for testing (IXIT): A statement made by the supplier or an implementor of an IUT which contains or references all of the information (in addition to that given in ICs) related to the IUT and its testing environment, which will enable the test lab
33、oratory to run an appropriate test suite against the IUT. An IXIT can take several forms: protocol IXIT, profile IXIT, profile specific IXIT, and information object IXIT. 5.15 test tool: Hardware and/or software, excluding the test suite itself, used to carry out or assist in carrying out the testin
34、g required. 5.16 means of testing (MOT): Hardware andor software, and the procedures for its use, including the executable test suite itself, used to carry out the testing required, 5.17 implementation under test (IUT): An implementation of one or more requirements specifications, being that part of
35、 a system which is to be studied by testing. 5.18 interoperability testing: Testing to assess the ability of two or more systems to exchange information and to make mutual use of the information that has been exchanged. 5.19 reference implementation: An implementation of one or more standards or spe
36、cifications, against which a Means of Testing and test tools for those standards or specifications are tested for the purpose of validation of those Means of Testing or test tools. 6 Acronyms This Supplement uses the following abbreviations. ASN. 1 Abstract Syntax Notation One ATS Abstract Test Suit
37、e 2 A series - Supplement 1 (09/98) ETS Executable Test Suite FD Formal Definition FDT Formal Description Technique IUT Implementation Under Test MOT Means of Testing MSC Message Sequence Chart PICS Protocol Implementation Conformance Statement PIXIT Protocol Implementation Extra Information for Tes
38、ting SDL Specification and Description Language TTCN Tree and Tabular Combined Notation 7 Developing high quality Recommendations 7.1 In preparing new Recommendations or making an assessment of the quality of existing Recommendations, the following aspects should be considered: Readability - This re
39、quires that a Recommendation is well structured and can be easily read and understood. This implies good use of the natural languages with adequate use of figures, examples and references. Completeness - A Recommendation should be complete in the sense that it includes all parts necessary for its im
40、plementation. This includes clearly identified, precise and unambiguous specifications, and may include the Abstract Test Suite, the Protocol Implementation Conformance Statement Proforma and the Protocol Implementation Extra Information for Testing Proforma. Correctness - Specifications should be e
41、rror-free and represent the intended behaviour; this applies especially to the parts of the Recommendation expressed using formal description techniques. Consistency - Different parts of the Recommendation or a set of related Recommendations should not contain contradictory information. Unambiguity
42、- A Recommendation should not be subject to different interpretations; implementations from different suppliers should be compatible; this is especially important where interoperability is required in a multi-vendor environment. Implementability - A specification should not be unnecessarily complex.
43、 This means that the specification should permit only a minimum number of optional features, avoiding those options whose sole purpose is to achieve consensus. The specification should be based on the best technical solution. Testability - If products are based on a specification contained in a Reco
44、mmendation, it should be possible to test whether the product conforms to the specification. Overview of the quality aspects 7.2 Upfront identification Each Study Group should identi upfi-ont during the formulation of the Study Group Questions and subsequently in the development phase of Recommendat
45、ions, which quality aspects need to be fulfilled based on market requirements. A check-list to facilitate this identification is contained in Annex A. A series - Supplement 1 (09/98) 3 As a general guideline, all Recommendations that address the interoperability of equipment, networks, protocols or
46、services should consider all quality aspects addressed here. 7.3 Formal Description Techniques Formal specifications should be made available in machine-readable format to allow companies to use their facilities for simulation, Validation, automatic code generation or other types of automatic proces
47、sing, should they wish to do so. Guidelines on the use of FDTs are contained in Recommendation Z.110. It provides criteria for their use and should, therefore, be taken as a reference in conjunction with this Supplement. It is planned to extend the scope of Recommendation Z. 110 to cover a wider ran
48、ge of applications developed by groups such as, OMG, TINA-C. Whenever a discrepancy between a natural language description and a FD, or between two FDs, is detected, the discrepancy should be resolved by changing the natural language description or the FDs without necessarily giving preference to on
49、e over the other(s). 7.4 Overview of the process The quality of Recommendations is closely connected with the use of Formal Description Techniques (FDTs) and the use of computer-based tools. The main components of the quality process are formal specifications, validation of specifications and testing of prototype implementations. Figure 1 illustrates the complete process. The main component of the process is the formal specification expressed using an FDT. In this process, a precise and unambiguous formal specification may first be produced from the natural language specifica
