Experiences with the use of the MSC language for complex system specifications have shown that certain extensions are necessary in order to arrive at sufficiently transparent and manageable descriptions. Extended HMSCs, where MSC reference symbols may either be presented by hypertext-like descriptions or, in an expanded form, as detailed MSCs, appear to be especially suitable for a compact and transparent MSC representation. For an effective usage of such advanced MSC constructs, a corresponding tool support seems to be mandatory where interactively the event structures of special paths can explicitly be expanded while others remain hidden as MSC references that contain solely textual descriptions. The name `HyperMSCs' is proposed for such extended HMSCs. Beyond that, the communication between MSC references, operator expressions or HMSCs demands a generalisation of the gate concept.