1、 International Telecommunication Union ITU-T Z.120TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (02/2011) SERIES Z: LANGUAGES AND GENERAL SOFTWARE ASPECTS FOR TELECOMMUNICATION SYSTEMS Formal description techniques (FDT) Message Sequence Chart (MSC) Message Sequence Chart (MSC) Recommendation ITU-
2、T Z.120 ITU-T Z-SERIES RECOMMENDATIONS LANGUAGES AND GENERAL SOFTWARE ASPECTS FOR TELECOMMUNICATION SYSTEMS FORMAL DESCRIPTION TECHNIQUES (FDT) Specification and Description Language (SDL) Z.100Z.109 Application of formal description techniques Z.110Z.119 Message Sequence Chart (MSC) Z.120Z.129User
3、Requirements Notation (URN) Z.150Z.159 Testing and Test Control Notation (TTCN) Z.160Z.179 PROGRAMMING LANGUAGES CHILL: The ITU-T high level language Z.200Z.209 MAN-MACHINE LANGUAGE General principles Z.300Z.309 Basic syntax and dialogue procedures Z.310Z.319 Extended MML for visual display terminal
4、s Z.320Z.329 Specification of the man-machine interface Z.330Z.349 Data-oriented human-machine interfaces Z.350Z.359 Human-machine interfaces for the management of telecommunications networks Z.360Z.379 QUALITY Quality of telecommunication software Z.400Z.409 Quality aspects of protocol-related Reco
5、mmendations Z.450Z.459 METHODS Methods for validation and testing Z.500Z.519 MIDDLEWARE Processing environment architectures Z.600Z.609 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T Z.120 (02/2011) i Recommendation ITU-T Z.120 Message Sequence Chart (MSC) Summary
6、 Scope/objective The purpose of recommending MSC (Message Sequence Chart) is to provide a trace language for the specification and description of the communication behaviour of system components and their environment by means of message interchange. Since in MSCs the communication behaviour is prese
7、nted in a very intuitive and transparent manner, particularly in the graphical representation, the MSC language is easy to learn, use and interpret. In connection with other languages it can be used to support methodologies for system specification, design, simulation, testing, and documentation. Co
8、verage This Recommendation presents a syntax definition for Message Sequence Charts in textual and graphical representation. An informal semantics description is provided. Application MSC is widely applicable. It is not tailored for one single application domain. An important area of application for
9、 MSC is an overview specification of the communication behaviour for real time systems, in particular telecommunication switching systems. By means of MSCs, selected system traces, primarily “standard“ cases, may be specified. Non-standard cases covering exceptional behaviour may be built on them. T
10、hereby, MSCs may be used for requirement specification, interface specification, simulation and validation, test case specification and documentation of real time systems. MSC may be employed in connection with other specification languages, in particular SDL. In this context, MSCs also provide a ba
11、sis for the design of SDL-systems. Status/Stability MSC is stable. This Recommendation is a maintenance update of the 2004 version correcting a number of errors and consolidating Appendix I into the main text. Otherwise it is intended to be the same as the 2004 version, which was a natural continuat
12、ion of its 1999 version, refining concepts including: extended data interface, and references to default SDL interface, defined in ITU-T Z.121; uni-directional time constraints; in-line high level expressions. Associated work Recommendation ITU-T Q.65 (2000), The unified functional methodology for t
13、he characterization of services and network capabilities including alternative object oriented techniques. Recommendation ITU-T X.210 (1993) | ISO/IEC 10731:1994, Information technology Open Systems Interconnection Basic Reference model: Conventions for the definition of OSI services. Recommendation
14、 ITU-T X.292 (2002), OSI conformance testing methodology and framework for protocol Recommendations for ITU-T applications The tree and tabular combined notation (TTCN). Recommendation ITU-T Z.100 (2002), Specification and Description Language (SDL). Recommendation ITU-T Z.121 (2003), Specification
15、and Description Language (SDL) data binding to Message Sequence Charts (MSC). UML 2.0, OMG 2003. ii Rec. ITU-T Z.120 (02/2011) History Edition Recommendation Approval Study Group 1.0 ITU-T Z.120 1993-03-12 X 1.1 ITU-T Z.120 Annex B 1995-03-06 10 2.0 ITU-T Z.120 1996-10-18 10 2.1 ITU-T Z.120 Annex C
16、1996-10-18 10 2.2 ITU-T Z.120 Annex B 1998-04-01 10 3.0 ITU-T Z.120 1999-11-19 10 3.1 ITU-T Z.120 (1999) Cor. 1 2001-12-14 10 4.0 ITU-T Z.120 2004-04-29 17 4.1 ITU-T Z.120 (2004) Amend.1 2008-09-19 17 4.2 ITU-T Z.120 (2004) Amend.2 2009-09-25 17 5.0 ITU-T Z.120 2011-02-13 17 Rec. ITU-T Z.120 (02/201
17、1) iii FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible f
18、or studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T stu
19、dy groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis
20、 with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory p
21、rovisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use
22、of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no p
23、osition concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, pr
24、otected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2011 All rights reserved. No par
25、t of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. iv Rec. ITU-T Z.120 (02/2011) Table of Contents Page 1 Introduction 1 1.2 Objectives of MSC . 1 1.2 Organization of the Recommendation 1 1.3 Meta-language for textual grammar . 2 1.4 Meta-l
26、anguage for graphical grammar . 3 2 General Rules . 6 2.1 Lexical Rules 6 2.2 Visibility and Naming Rules 12 2.3 Comment 13 2.4 Drawing Rules 14 2.5 Paging of MSCs 15 3 Message Sequence Chart document . 15 4 Basic MSC 17 4.1 Message Sequence Chart 17 4.2 Instance . 22 4.3 Message 24 4.4 Control Flow
27、 . 27 4.5 Environment and gates . 32 4.6 General ordering . 39 4.7 Condition 41 4.8 Timer 43 4.9 Action . 46 4.10 Instance creation . 47 4.11 Instance stop . 48 5 Data concepts 48 5.1 Introduction 48 5.2 Syntax interface to external data languages . 48 5.3 Semantic interface to external data languag
28、es 51 5.4 Declaring data . 53 5.5 Static data . 54 5.6 Dynamic data 55 5.7 Bindings 56 5.8 Data in message and timer parameters . 58 5.9 Data in instance creation parameters 60 5.10 Data in action boxes . 60 5.11 Required data types 61 Rec. ITU-T Z.120 (02/2011) v Page 6 Time concepts . 61 6.1 Timed
29、 semantics . 62 6.2 Relative timing . 62 6.3 Absolute timing 62 6.4 Time domain . 63 6.5 Static and dynamic time variables 63 6.6 Time offset 63 6.7 Time points, measurements, and intervals . 63 6.8 Time points . 63 6.9 Measurements . 64 6.10 Time interval 64 7 Structural concepts 67 7.1 Coregion .
30、68 7.2 Inline expression . 69 7.3 MSC reference 73 7.4 Instance decomposition 77 7.5 High-level MSC (HMSC) . 85 8 Message Sequence Chart Document 90 8.1 MSC Documents 90 8.2 Instance decomposition 91 8.3 Instance inheritance 93 9 Simple Message Sequence Charts 94 9.1 Basic MSC 94 9.2 Message overtak
31、ing 95 9.3 MSC basic concepts 96 9.4 MSC-composition through labelled conditions 97 9.5 MSC with time supervision 99 9.6 MSC with message loss 101 9.7 Local conditions . 101 10 Data . 103 11 Time 106 12 Creating and terminating processes 110 13 Coregion . 110 14 General ordering . 111 14.1 Generaliz
32、ed ordering within a coregion . 111 14.2 Generalized ordering between different instances . 112 vi Rec. ITU-T Z.120 (02/2011) Page 15 Inline expressions . 113 15.1 Inline expression with alternative composition 113 15.2 Inline expression with gates . 115 15.3 Inline expression with parallel composit
33、ion . 116 16 MSC references 117 16.1 MSC reference 117 16.2 MSC reference with gate 119 17 High-level MSC (HMSC) . 119 17.1 High-level MSC with free loop 119 17.2 High-level MSC with loop . 120 17.3 High-level MSC with alternative composition . 121 17.4 High-level MSC with parallel composition 123 A
34、ppendix I Application of MSC . 125 I.1 Introduction 125 I.2 Problems . 125 I.3 General undecidable results 129 I.4 Syntactical description of MSC subclasses 129 I.5 Summary of results . 134 I.6 Recommendations 135 Bibliography. 136 Rec. ITU-T Z.120 (02/2011) 1 Recommendation ITU-T Z.120 Message Sequ
35、ence Chart (MSC) 1 Introduction 1.2 Objectives of MSC Message Sequence Charts (MSC) is a language to describe the interaction between a number of independent message-passing instances. The main characteristics of the MSC language are the following. MSC is a scenario language. An MSC describes the or
36、der in which communications and other events take place. Additionally, it allows for expressing restrictions on transmitted data values and on the timing of events. MSC supports complete and incomplete specifications. It has the possibility to describe incomplete behaviours used in early analysis an
37、d for documentation purposes. MSC is a graphical language. The two-dimensional diagrams give overview of the behaviour of communicating instances. The textual form of MSC is mainly intended for exchange between tools and as a base for automatic formal analysis. MSC is a formal language. The definiti
38、on of the language is given in natural language as well as in a formal notation. MSC is a practical language. MSC is used throughout the engineering process. Its use ranges from domain analysis and idea generation via the requirements capture and design phases to testing. MSC is used in slightly dif
39、ferent ways in the various phases, and it is important that MSC has formal expressive power as well as intuitive appearance. MSC is widely applicable. It is not tailored for one single application domain. MSC supports structured design. Simple scenarios (described by Basic Message Sequence Charts) c
40、an be combined to form more complete specifications by means of High-level Message Sequence Charts. MSCs are gathered in an MSC document. A modular design of scenarios is supported by mechanisms for decomposition and reuse. MSC is often used in conjunction with other methods and languages. Its forma
41、l definition enables formal and automated validation of an MSC with respect to a model described in a different language. MSC can, for example be used in combination with SDL and TTCN. The usual interpretation of a scenario specified in an MSC is that the actual implementation should at least exhibi
42、t the behaviour expressed in the scenario. Alternative interpretations are also possible. An MSC can, for example, be used to specify disallowed scenarios. 1.2 Organization of the Recommendation The document is structured in the following manner: In 2, general rules concerning syntax, drawing and pa
43、ging are outlined. In 3, a definition for the Message Sequence Chart document is provided. Section 4 contains the definition of Message Sequence Charts and the basic constituents, i.e., instance, message, general ordering, condition, timer, action, instance creation and termination. Section 5 contai
44、ns the data concepts and Section 6 defines the concepts for Time. In 7, higher level concepts concerning structuring and modularisation are introduced. These concepts support a top down specification and permit a refinement of individual instances by means of coregion ( 7.1) and instance decompositi
45、on ( 7.4). Inline expressions are defined in 7.2 and MSC references 7.3. High level MSC ( 7.4) permits MSC composition and reusability of (parts of) MSCs on different levels. In 8, examples are provided for all MSC-constructs. Annex A contains an index for the s and non-terminals. 2 Rec. ITU-T Z.120
46、 (02/2011) 1.3 Meta-language for textual grammar In the Backus-Naur Form (BNF) a terminal symbol is either indicated by not enclosing it within angle brackets (that is the less-than sign and greater-than sign, ) or it is one of the two representations and . The angle brackets and enclosed word(s) ar
47、e either a non-terminal symbol or one of the two terminals or . Syntactic categories are the non-terminals indicated by one or more words enclosed between angle brackets. For each non-terminal symbol, a production rule is given either in concrete textual grammar or in concrete graphical grammar. For
48、 example := inst A production rule for a non-terminal symbol consists of the non-terminal symbol at the left-hand side of the symbol :=, and one or more constructs, consisting of non-terminal and/or terminal symbol(s) at the right-hand side. For example, and and in the example above are non-terminal
49、s; inst is a terminal symbol. Sometimes a symbol includes an underlined part. This underlined part stresses a semantic aspect of that symbol, e.g., is syntactically identical to , but semantically it requires the name to be a Message Sequence Chart name. At the right-hand side of the := symbol several alternative productions for the non-terminal can be given, separated by vertical bars (|). For example, := | expresses that an is either a or a . Syntactic elements may be grou
