You can easily get various schema information from the SQL statement by using the system catalog virtual class. For example, you can get the following schema information by using the catalog virtual class.
-- Classes that refer to the 'b_user' class
SELECT class_name
FROM db_attribute
WHERE domain_class_name = 'db_user';
-- The number of classes that the current user can access
SELECT COUNT(*)
FROM db_class;
-- Attribute of the 'db_user' class
SELECT attr_name, data_type
FROM db_attribute
WHERE class_name = 'db_user';