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 presented 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. Coverage 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 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. Thereby, 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 basis for the design of SDL-systems. Status/Stability MSC is stable. This Recommendation is a natural continuation of its 1999 version, refining concepts including: extended data interface, and references to default SDL interface, Z.121; uni-directional time constraints; in-line high level expressions. Associated work - ITU-T Recommendation Q.65 (2000), The unified functional methodology for the characterization of services and network capabilities inlcuding alternative object oriented techniques. - ITU-T Recommendation X.210 (1993) ISO/IEC 10731:1994, Information technology - Open Systems Interconnection - Basic Reference model: Conventions for the definition of OSI services. - ITU-T Recommendation X.292 (2002), OSI conformance testing methodology and framework for protocol Recommendations for ITU-T applications - The tree and tabular combined notation (TTCN). - ITU-T Recommendation Z.100 (2002), Specification and Description Language (SDL). - ITU-T Recommendation Z.121 (2003), Specification and Description Language (SDL) data binding to Message Sequence Charts (MSC). - UML 2.0, OMG 2003.