Core Data syncing: This is where the rubber meets the road for
database-backed applications. Core Data is the application-level
database framework supplied by OS X and iOS that provides the
means for applications to store items, and data about those items,
in a single database. Yojimbo, our product, was one of the very
first to ship using Core Data storage — we’ve used it since
2006, and it works great for storing data locally in the way that
the product needs it to. Syncing database changes with iCloud,
however, is a very complicated and difficult job for Core Data.
That’s really the heart of it. Core Data really does “just work” for local storage, both on OS X and iOS, but that’s not the case with Core Data and iCloud.