Important note: GCL is not really a symbolic model. It contains only components (elements and relationships). Whenever a symbolic model for communication is built (e.g. a sentence), one needs to choose components from GCL. As any use of GCL is materialised in a symbolic model and because there is no proper word for it, GCL is considered by extension a symbolic model. Technology uses models on a very large scale. Image models have initially been used, but nowadays, due to the high costs of the image models and for other reasons, symbolic models and the use of computers are favoured (e.g. symbolic models are built currently for buildings, suspension bridges, airplanes and spacecrafts, with the help of computers). For training purposes, symbolic models are built and used for simulation of nuclear plants, or flight behaviour, or anything, where it is necessary that future crew/staff to gain experience beforehand. Present technology is based in fact almost exclusively on symbolic models. Application 3: From the iron to the space shuttle Apparently an iron is too simple to require a design based on a symbolic model. False. Let's take a simple technological detail: the holes used for steam exhausts for moisturising the tissue. Some questions are, e.g. how many holes it needs, where, what shape and dimensions are needed for uniform moisturising of the tissue with minimum water consumption and at lowest costs. Clearly, it is possible to build analogic models, which can be tested experimentally. Based on the analogic (image) models one can obtain certain results, but there is no guarantee that the optimal solution was found. The existing image model cannot be modified, as such. If we want to make any change in the image model we have to rebuild it from scratch, as we already know, which implies time and money. The vaporisation and dispersion process of the steam through a complex structure as the surface of the iron, tissue and the support, is very complex. Physicists, based on symbolic models, with help of computers, solve this type of problem. The rebuilding of the model in order to find a better solution is far simpler on a symbolic model, than on an image model. If in the case of an iron, the highest risk is that the customers won't buy the non-performing iron, in other cases the risks involved are unacceptable. For instance, the space shuttle was 'verified' for reentering the atmosphere on a symbolic model. This phase of the flight, by far the most dangerous, would have been impossible to test before the actual flight. The crew was trained on symbolic models in all the phases of the flight, and in all normal and exceptional situations. The astronauts have learned to fly for reentering the atmosphere, based mainly on training on symbolic models.