Collaborative tagging systems are an example of socially-aware, self-organising, complex systems. The multi-agent systems paradigm coordinated by self-organisation mechanisms has been used as an effective way for the design and modeling of such systems. Existing tagging systems do not take full advantage of their complex systems characteristics, especially in adapting to their environment and allowing emergence. In this paper, we propose a model for designing a tagging system, using a multi-agent system approach, governed by the co-evolution of the social and spatial organisations of the agents. We show how the proposed system has new functionalities that could enhance current collaborative tagging systems.