[...] * In current practice the most frequently used is a decision of the development team based on the results of the various tests and evaluations conducted as part of the model development process. Another approach is to engage users in the choice and validation process. At any rate, conducting model validation concurrently with the development of the simulation model enables the model development team to receive inputs earlier on each stage of model development. ↵\↵* Therefore, ICT Tools for speeding up, automating and integrating model validation process into policy model development process are necessary to guarantee the validity of models with an effective use of resources. It has finally to be noticed that model validation is not a discrete step in the simulation process. It needs to be applied continuously from the formulation of the problem to the implementation of the study findings as a completely validated and verified model does not exist.