This work presents a methodology to formally model and to build collaborative three dimensional interaction tasks in virtual environments using three different tools: Petri Nets, Interaction Technique Decomposition taxonomy and Object-Oriented concepts. The user operations in the Virtual Environment are represented as Petri Net nodes and these nodes, when linked, represent the interaction process stages. The integration of these approaches results in a modular application, based on the Petri Nets formalism that allows for specification of collaborative interaction tasks, and also the reuse of developed blocks in new virtual environment projects.