Let me try to answer this. Anyone else can jump in as far as their opinion on Spark.
Spark is indeed a platform developed by DoFactory. Spark offers a better and faster alternative to the Entity Framework. However, it does much more. It provides the architecture for, say 80% of the application including Domain objects, Repository and Service Layers, and tools and techniques related to Security, Business Rules, Transactions (Unit of Work Pattern), Caching, OAuth, and more.
Anyhow, the REST interface in the Spark reference application is built on Web API. This means that if you use .NET 4.5 you can indeed build your own REST implementation on a 'Patterns in Action'-type architecture. You will need to handle your own data access for which you could use Entity Framework, LINQ-to-SQL,or ADO.NET or anything else.
Hope this helps.
Jack Poorte, Sep 26, 2013