In this contribution we present a theoretical approach which has been utilized to inform the coordination of the development of complex systems. Coordination is regarded as a form of human activity in which individual and social aspects as well as technical ones need to be considered. We analyze human activity from an interaction point of view in which various types of signs mediate the relation between individual cognition and phenomena in the environment. The sign-mediated interaction is apprehended as having a connectional, conceptual and linguistic facet. From a cognitive and semiotic analysis of these facets, we conjecture that the following constituents are fundamental for human activity: intersubjectivity, experiential learning, contextuality, spatiality, temporality, stabilizing core and tool usage. These constituents are employed in structuring human activity from a coordination point of view as activity domains. A framework for articulating activity domains is described. Thi...