A CLOS/SQL class may also be given the KnowledgeWorks mixin class, enabling rules to refer to these objects as if there were no database present. However, their database functionality carries over transparently. For example, consider the case where a slot in the database class is designated for deferred retrieval from the database. When the rulebase queries the contents of the slot, a database query will automatically be generated to retrieve and fill in the value of the slot, and the rulebase will continue as if the value had been there in the first place.
Details of the LispWorks Common SQL interface can be found in the LispWorks User Guide and Reference Manual .
KnowledgeWorks and Prolog User Guide (Unix version) - 6 Dec 2011