To obtain value from the graphical representations that are used by different stakeholders during the system development process, they must be integrated. This is important to achieve a holistic understanding about system specification. Integration can be reached via modelling process. Currently, most of information system modelling methods present different modelling aspects in disparate modelling dimensions and therefore it is difficult to achieve semantic integrity of various diagrams. In this paper, we present semantically integrated conceptual modelling method for information system analysis and design. The foundation of this modelling method is based on interactions. This way of modelling provides possibility of integration of business processes and business data. The inference rules of interactions help in reasoning about the decomposition of concepts. In this method, decomposition of the system is graphically described as classification, inheritance or composition of organizational and technical system components.