An important aspect with respect to the implementation of typed feature structures is the static typing of type systems. A type system is static if all type inference and checking can be performed at compile-time [Carpenter1992]. The advantage of static typing resides in the increased efficiency of feature structure implementation, an advantage also seen in programming languages, where the most efficient languages, like C, require static typing of their type systems.
For typed feature structures, static typing is ensured when unification of well-typed feature structures results in a well-typed feature structure.