Development of an MSC/UML Test Format

The development of an Message Sequence Chart (MSC) based graphical representation of the Tree and Tabular Combined Notation (TTCN) is part of the ETSI project STF 156 on 'Specification of a Message Sequence Chart/UML format, including validation for TTCN-3' (The term TTCN-3 denotes the third edition of TTCN). Experiments with different kinds of MSC representations show that certain extensions of the MSC language are requested in order to obtain a sufficiently transparent and readable MSC test format. Extended HMSCs where reference symbols may either contain hypertext-like descriptions or, in the expanded form, the detailed event structure of basic MSCs appear to be especially suitable for a compact and transparent test case representation. For an effective usage of such advanced MSC constructs, a corresponding tool support appears to be mandatory where the event structure of special paths in the test case is described explicitly while others are hidden in MSC references containing pure textual descriptions. We propose the name 'HyperMSCs' for such extended HMSCs. A significant difference between the standard TTCN format and the MSC format refers to the behavior description of several test components. In the concurrent case, a TTCN test case describes the communication of the main test component (MTC) and its ports. The behavior description of parallel test components (PTCs) is provided by separate functions. A simple translation of this partitioning into MSCs leads to separate MSC specifications for the different test components which have to be merged somehow by an appropriate join operation. However, such a 'local' view does not make use of the main advantage of the MSC language. The strength of MSC lies in the immediate description of the communication behavior which is provided by a 'global' view including all test components in the same diagram. The translation of TTCN into the MSC format is demonstrated using a simple example taken from the Inres protocol.