Process is linear in t h e n u m b e r o f e l e m e n z s in ~he input message, . the realization decision for each element is m a d e only once and m a y not be revised. The representation for pending realization decisions and planned linguistic actions (the results of earlier decisions) is a surface-level syntactic phrase structure augmented by explicit labelings for its constituent positions (hereafter referred to as the tree).3 This working-structure is used simultaniously for control (determining w h a t action to take next)
