What is an MSC?
The Message Sequence Chart language (MSC) is a graphical and textual language for the description and specification of the interactions between system components. The main area of application for the Message Sequence Chart language is as an overview specification of the communication behaviour of real-time systems, in particular telecommunication switching systems. Message Sequence Chart diagrams (MSCs) may be used for requirement specification, simulation and validation, test-case specification and documentation of real-time systems. MSCs are often used in combination with other System Design Languages , in particular the ITU Specification and Description Language.You can learn the basics of the MSC by reading the short pdf tutorial on MSC, or the tutorial on MSC'96 (which also has an accompanying set of MSC'96 tutorial slides), or the TIMe MSC-92 tutorial in HTML (or as a PDF)or the TIMe MSC-96 tutorial in HTML (or as a PDF).
MSC was significantly updated in 1999 to MSC-2000.
Some tutorial slides
can be found at
http://www.sdl-forum.org/MSC2000present/index.htm.
You can also read a tutorial on the formalization of MSC, a paper on Algebraic Semantics of Basic Message Sequence Charts, and a thesis "Message Sequence Chart - Syntax and and Semantics" by Michel A. Reniers can be found at http://www.win.tue.nl/~michelr/Files/proefschrift.pdf.