CSDL, SSDL and MSL sections in an EDMX file

• CSDL (Conceptual Schema definition language) is the conceptual abstraction which is exposed to the application.
• SSDL (Storage Schema Definition Language) defines the mapping with your RDBMS data structure.
• MSL (Mapping Schema Language) connects the CSDL and SSDL.

CSDL, SSDL and MSL are actually XML files.