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Professional ADO.NET 3.5 with LINQ and the Entity Framework by Roger Jennings

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Chapter 10. Defining Storage, Conceptual, and Mapping Layers

The primary feature that distinguishes the ADO.NET Entity Framework (EF) from the myriad other object/relational mapping (O/RM) tools for .NET is its layered approach to the mapping process for creating an Entity Data Model (EDM). Layered mapping prevents simple changes to the relational data store's schema from causing changes in the EDM object graph's structure that force source code modifications. For example, DBAs can split or combine tables without requiring rewriting code if the changes can be accommodated by modifying the XML content of the storage and mapping layers only. Entity SQL (eSQL) queries at the EntityClient level and eSQL or LINQ to Entities queries at the ObjectServices level use the same mapping files.

The EDM is part of Microsoft's wide-ranging Entity Data Platform strategy that Michael Pizzo, a data architect in Microsoft's Data Programmability Group, described in an April 2007 blog post entitled "Microsoft's Data Access Strategy."

Microsoft envisions an Entity Data Platform that enables customers to define a common Entity Data Model across data services and applications. The Entity Data Platform is a multi-release vision, with future versions of reporting tools, replication, data definition, security, etc., all being built around a common Entity Data Model.

Successive releases are expected to include SharePoint lists, Web services, and well-established XML document formats, such as Atom, InfoPath, or ...

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