From my understanding I though the data layer should isolate the Data Technology from the rest of the application, for me this also include the schema in this case the data entity. Recently I've been looking at the Silk project from Patterns & Practices http://silk.codeplex.com/, and noticed that data entities are translated in the business layer rather than in the data layer.
I think the advantage is that it avoid the data layer to reference an assembly containing the business model. However the fact that it expose data entities publicly is from my understanding a disadvantage because external components may be dependent of the data schema.
I would like to understand why they translate data entities in the business layer and what are the advantages?
I know that they use code first entity framework, so that the entities doesn't have data technology related dependency, however there responsibility is still to structure the data model not the business model.