A few common thoughts. I think it is not only necessary to improve already existing special KeyPath syntax to make it available in Core Data. Now we have Swift Server APIs Project (https://swift.org/server-apis/). May be it is time to begin such preparation steps in collections/databases direction and KeyPath improvements will be only part of future Swift 10 databases support? lynch.sft proposal can be a good start for it but in this case it will be only first step of big problem. It can be premature in context of Swift 5 but I use Swift and Core Data actively and lack of safety is big problem. It is good discussion in any case.