diff --git a/Database.md b/Database.md
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 # Database
 
+Used database schema is generated by ORM framework Doctrine from ReCodEx API code. Tables are directly mapped to _entities_, which are PHP classes annotated with data provided by ORM framework. In the following text there is a brief description of each such entity. There may be some additional database tables for many-to-many relations between entities, but these tables are not discussed in detail because there are only two columns with keys to both related tables in each one.
+
 ## Assignment
 
 ## Comment