Purpose - The importance of context dependent modelling of complex systems, depending on the observer's point of view will be discussed. Thus, context is synonymous for the content of a problem in a frame of the goals, starting points and ways to achieve these aims. In this light, difficulties of model validation and a general method how to overcome them was discussed. The relations among subject object - model in the light of a systems approach; Charles Sanders Peirce's triad principle and the semiotic principle of communication was presented. Design/methodology/approach - The appropriateness of a system dynamics methodology, which is due to its transparency and clarity an excellent tool for modelling of complex systems. Findings - In the paper the equivalence of different methodologies was shown, whose differences and similarities can be judged only in context of a problem and the aims of researches. For illustration, the methodology is applied to a tourism system, which possesses the typical properties of global and local organisations. A verbal description of a tourism problem is followed by a causal loop diagram, which helps to discuss the problem categorically. Practical implications - As the methodology is implemented using quantitative model and POWERSIM tools; it offers the solution of national tourism strategy implication, selected from different scenarios. Originality/value - This paper presents a simulation model of the tourism in a frame of system dynamics, developed from qualitative models, as an illustration of the discussed methodology.
