I have successfully used Oracle with Olingo from java JPA and EclipseLink
I guess that you didn't define an entity set (Books) for an entity type (Book for example) within your EDM provider. To check this, you can have the look at the root URL of your service (for example http://services.odata.org/V4/OData/OData.svc/). I think that, in your case, no collection entry is defined...
Yes this is perfectly possible, just include the child path in the $filter e.g. say we have a header Aircraft and child Airline /Aircraft would list all aircraft for all Airlines Aircraft?$filter=Airline/Code eq 'BA' would list all Aircraft for BA only For you 2nd query, to return the child and...
A key is required for an entityType in olingo and odata, because if there is no unique key for an entity then we won't be able to use getEntity (to query the data of just one entity from a given entitySet) on it , as well as navigation properties and...
it is a bit long story about the missing Microsoft.OData.Service 6.x, it does exist but is not officially released to public. unlike Its previous version that is for odata V3 protocol, 6.x library is for odata V4 protocol, since Microsoft OData team decided to move away from WCF Data service,...