MESSAGE SEQUENCE CHART COREGION ENHANCEMENT

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Motorola

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Abstract

Message sequence charts (MSCs) are used extensively in the development of complex systems to describe the flow of information between func- tional units in a system.

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MOTOROLA Technical Developments

MESSAGE SEQUENCE CHART COREGION ENHANCEMENT

by Bhavesh G. Patel, Gregory A. Dertz, Surender Kumar and Rick Rohles

INTRODUCTION

  Message sequence charts (MSCs) are used extensively in the development of complex systems to describe the flow of information between func- tional units in a system.

  The ITUT organization has standardized the use of MSCs in their 2.120 publication. In this stan- dard, Functional Entities are drawn as vertical columns and the exchange of information is shown using arrows (messages) initiated from one column

and being consumed by another column. In certain situations, the ordering of messages is not important or unspecified in the MSC. For this situation, Z. 120 introduces the concept of "coregion", where the region in which message ordering is unspecified or unimportant is denoted by a dashed line in a column bracketing all such messages. In Figure 1, the order- ing of Message 1 and Message 2 is not specified. The messages can be initiated in any order by Functional Entity I (FE 1). Also the messages can be consumed in any order by FE 2.

I _I

Message I I d

I I I I I I

I

I

Message 2 '

I I

Fig. 1 Co-regions in Message Sequence Charts

(7 Motorola. Inc. ,997

164 December 1997

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MOTOROLA Technical Developments

PROBLEM

  The existing Z. 120 Message Sequence Chart co- region specification does not provide a means to specify the valid permutations of messages within a coregion.

  Z. 120 introduces the coregion concept and only specifies that messages initiated from or consumed by a coregion can be in any order. However, there is no mechanism to specify which message order permutations are valid within a coregion. It assumes that all permutations are valid.

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SOLUTION

  This paper describes a mechanism for MSCs that adds specificity regarding the valid permuta- tions of messages being initiated from and/or consum...