  We propose a treatment of coordination based on the concepts of functor,
argument and subcategorization. Its formalization comprises two parts which are
conceptually independent. On one hand, we have extended the feature structure
unification to disjunctive and set values in order to check the compatibility
and the satisfiability of subcategorization requirements by structured
complements. On the other hand, we have considered the conjunction {\em et
(and)} as the head of the coordinate structure, so that coordinate structures
stem simply from the subcategorization specifications of {\em et} and the
general schemata of a head saturation. Both parts have been encoded within HPSG
using the same resource that is the subcategorization and its principle which
we have just extended.
