The Perk database connects to a database using OKBC operations [10] and refers to frames in the database by loading frames into the main memory for inferences. Its later versions employ object views and uses indexes to point to the required frames. EcoCyc system and PARKA-DB keep frames in relational database and load them into the main memory when required. Sophia also keeps frames in relational database and use SQL query for frames loading. All of them do not have the inference capability on the database side. Only tuples of relations are transfer to the expert systems.