The tension in planning definite reference derives from the need to serve both the referring and informing functions. The referring function is mainly concerned with the Sem slot of the NP-specification: the task is to point uniquely at the filler of this slot, distinguishing it from all other entities. The planner may need to use any or all of the syntactic slots of the nucleus to do this.
On the other hand, the informing function is primarily concerned with the Agenda slot - the function is satisfied if all the facts in this slot are expressed somewhere in the NP (whether nucleus or satelite). While these facts can be placed in satelite position, it is often more coherent to place them within the nucleus.
As such, the two functions are in competition for the syntactic slots, and structural decisions good for one function may be sub-optimal for the other. The usual approach is to allow the referring component to go first, generating the desired referring form. Then, the needs of the informing component are fitted into this structure.
However, we have found it far more rewarding to allow all syntactic decisions to be mutually negotiated between the two functions. Below, we describe the definite description algorithm as used in ILEX.