I was wondering if somebody would explain the difference between create_rules_index and create_entailment? I have read through the Semantic Technologies Developer's Guide, but I am still unclear as to when/why you would choose one over the other. They both seem to create a rules index and they both seem to utilize any user created rules.
create_rules_index was the inferencing API in 10gR2. create_entailment was introduced in 11g, and is the recommended API for all inferencing, for performance and other reasons. create_rules_index is available for backward compatibility reasons.