Scandinavian Contributions to Object-Oriented Modeling Languages

The history of Scandinavian contributions to modeling languages is interesting in many respects. The most interesting part of the history is that some of mechanisms were conceived very early, years before modeling became mainstream. It is well-known that object-orientation started with SIMULA in 1967, but it is less known that SIMULA formed the basis for a modeling language already in 1973, and that the Ericsson AXE software structure (1976) was one of the foundations (via SDL) for composite structures in UML2. It is also interesting that there has been a development towards making mechanisms less particular: while early modeling languages had special structuring mechanisms, UML2 now cover this by composite classes. In addition, early modeling languages were executable, in fact they were combined modeling – and programming languages. After a period where modeling was just for the purpose of analysis and design, the trend is now towards executable models, i.e. almost going back to the original Scandinavian approach.