Language involves both structure and process. Giving each its due, we present a cognitive process model and show how its empirical success is related to claims about syntactic structure. Innate constraints on syntax are a central issue in linguistic theory, so it is a matter of concern that a widely accepted view of phrase structure constraints (X-bar theory) appears to be violated in some recent comprehension experiments with children. However, what is directly observed in the experiments is not a syntactic structure but the execution of a plan. We present a language of process for representing such plans and thereby provide a unified explanation of several developmental phenomena, including the results of the above experiments and of new experiments suggested by our approach. The explanation is in terms of the cognitive resources required to formulate and execute a plan. Since the explanation is based on nonsyntactic processing, the children's syntax need no longer be held faulty. This conclusion invigorates the claim that the range of phrase structures available to children is biologically constrained.