Message Sequence Chart: Composition Techniques versus OO-Techniques - 'Tema con Variazioni'

Structural concepts for Message Sequence Charts (MSCs), i.e., composition, types, inheritance, and virtuality, are applied to a telecom example provided by the public switching systems division of the Siemens AG. The example contains several variations of the peripheral parts of an initial MSC which may be combined independently. The independent combinations of the peripheral variations are described by means of several new composition operators and by using object-oriented techniques (OO-techniques), i.e. types, inheritance, and virtuality. A comparison of both techniques shows that composition operators may provide a compact, easy, but abstract description, whereas some OO-techniques allow a graphical, intuitive, but not compact specification. Typical OO-techniques like inheritance and virtuality seem to be less fruitful for the description of at least the provided example. A combination of composition operators and OO-techniques, e.g., a variant type concept employing the alternative composition operator, may combine the advantages of both techniques.