The backing store uses relational tables and SQL data types for ease of maintenance. The SQL (DDL) scripts use ANSI SQL type definitions (where supported by the target DBMS product).
Each ontology type in the backing store has its own primary table and zero or more second-level tables. There are only two levels of tables, which makes the database easier to manage and easier to understand. Because the backing store adheres to SQL standards and a straight-forward structure, standard database tools can be used to view backing store data.
Secondary tables are used for complex properties, that is, arrays, properties with history, and concept relationship properties. Each array and history-enabled property has a separate table. Only primitive properties are stored in the primary table.