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