A persistent object service (POS) that interfaces to a set of one or more relational database management systems. A persistent object is mapped to one or more tables in a relational database based on the object's attribute types and the object's relationships with other objects. If the object inherits from another object, the mapping creates multiple tables, a top level table for base attributes, and a set of one or more child tables that contain extended attributes of the inherited objects. A routine for storing an object converts persistent object operations to a sequence of SQL statements for storing the object in the relational database.