Guide to Entity Framework with

How is the EDM represented?
The EDM uses the following 
three types of XML files to represent the C-Space, 
C-S Space, and the S-Space respectively:
• 
Conceptual Schema Definition Language (.CSDL)
: This represents the C-S 
Space and is used to map the entity types used in the conceptual model
• 
Mapping Schema Language (.MSL)
: This represents the C-S Space and is 
used to map the logical model to the conceptual model
• 
Store Schema Definition Language (.SSDL)
: This represents the S-Space
and is used to map the schema information of the Logical layer

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Introducing the ADO.NET Entity Framework
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]
If you use the ADO.NET EDM Designer tool to generate your EDM, you 
will have one 
.edmx
file that contains the CSDL, MSL, and SSDL sections 
bundled into one single file. At runtime, the 
.csdl
, 
.msl
, and 
.ssdl
files are created in the application's output directory.
These files store the metadata information as XML for each of the preceding layers.
You can also create abstract and complex types in your EDM. You can 
derive from an abstract type to create sub-types, but no instance of the 
abstract type can be created. You can also create complex types. That is, 
types that don't have any identity of their own. A typical example of a 
complex type is the 
Address
type.
We will skip further discussion on each of the sections of an EDM until 
Chapter 3
, 
Entities, Relationships, and the Entity Data Model
.
The Object Model (O-Space)
When working with Entity Framework, you will have an Object Model on top
of all the EDM layers. You need to model the Object Model using .NET objects. 
The following figure illustrates how the Object Model fits in with the EDM layers:
The Object Model or the O-Space
The O-C Mapping Layer
The Mapping Layer or the C-S Space (Modeled using MSL)
The Logical Model or the S-Space (Modeled using SSDL)
The Conceptual Model or the C-Space (Modeled using CSDL)
The Object Model and its relationship with other layers

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Chapter 1