Maintaining awareness is central to effective coordination and collaboration in complex human activities, but pervasive computing environment has not adequately addressed this requirement from a formal design perspective. Existing awareness solutions work only for relatively small-scale collaboration in traditional workplace, and they suffer from either inflexibility or lack of scalability if applied to pervasive computing environment. Based on our analysis of awareness life cycle, we propose a model of event-based awareness promotion mechanism. Our model extends focus-nimbus model and reaction-diffusion model with computational reasoning of dependencies and diffusion paths. The model is partially validated through implementation of our experimental environment, DACE (Dependency-based Awareness and Coordination Environment), which supports belief tracking, updates, and reasoning tasks and enhance the cognitive capability in awareness interpretation and use. Key principles of the DACE system are explained through a hypothetical scenario of search and rescue exercise typical in emergency response applications.