Many computation-intensive scientific applications feature complex workflows of distributed computing modules with intricate execution dependencies. Such scientific workflows must be mapped and executed in shared environments to support distributed scientific collaborations. We formulate workflow mapping as an optimization problem for latency minimization, whose difficulty essentially arises from the topological matching nature in the spatial domain, which is further compounded by the resource sharing complicacy in the temporal dimension. We conduct a rigorous analysis of the resource sharing dynamics in workflow executions, which constitutes the base for a workflow mapping algorithm to minimize the end-to-end delay. The correctness of the dynamics analysis is verified in comparison with an approximate solution, a dynamic system simulation program, and a real network deployment, and the performance superiority of the proposed mapping solution is illustrated by extensive comparisons with existing methods using both simulations and experiments.