- The current indexing system is largely prepared for secondary
indexes. This implies that if there are many clauses that match a given
key, the system could (JIT) create a secondary index. This secondary
index could exploit another argument or, if the key denotes a functor,
an argument inside the compound term.
- The `special cases' can be extended. This is notably attractive for static predicates with a relatively small number of clauses where a hash lookup is too costly.