Interfaces are something you can use with Telerik OpenAccess ORM in a two different ways. First, you can create interfaces in your Visual Designer, so that they will be part of the automatic code generation and the properties will be persistent. This functionality is not finalized yet - you will not be able to use the classes implementing an interface in a polymorphic manner. We are planning to include this feature in one of the future releases.
The other option would be to define the interfaces separately and implement them in partial classes (for your Domain Classes), which will be relatively independent from the auto-generated classes. This way you will prevent your implementation from being replaced by the code generation. The disadvantage is that the fields of those interfaces will not be persistent at all.
As per the abstract classes, they do not have direct representation in the Visual Designer, so you will have to follow the partial classes approach. In case your abstract classes have some persistent properties, you can model them as normal Domain Classes and limit their usage otherwise, like a private constructor for example.
Do not hesitate to get back to us if you have any questions.
the Telerik team