For many years, the battle cry of those fed up with the implementation of models in computer programs was “modular modelling!”. If we had a modular modelling system, it was argued, then models could be easily constructed from a number of pre-programmed modules, and the effectiveness of the community as a whole would be greatly increased by the sharing of these modules, avoiding huge duplications of effort.
The submodel concept in Simile supports modular modelling. You can open up a separate window for a submodel (say, a vegetation submodel); clear the contents of the submodel (by doing File: New), then load a different vegetation model into the submodel window. Influence links with the rest of the model can then be made one by one.
Furthermore, Simile supports plug-and-play modularity (which is what is normally meant by “modular modelling”). If two or more vegetation submodels have been designed to share a common set of influences (in and out) with the rest of the model, then the information about this interfacing can be stored in a file (an interface specification file). When you next load one of the submodels from a file, you simply refer to the interface specification file, and all the influence links are made in one quick operation.