I'm still stuck on this. I've tried to flatten out the relationship, same error. I recreated the test app using the Document architecture, same issue. There is no "custom" code in my app, nor is there any in the EventManager that would cause things to be different.

I simply cannot see the "the answer." (providing there is an answer)

You might get more response posting about this on one of the developer mailing lists - start at lists.apple.com

Thanks hayne! I'll give that a shot.

Again, thanks hayne - I wasn't aware of the "lists." On the MS Windows side, all is done by forum and not by email lists. A bit easier in my mind, however, it gets the job done.

At any rate, I did get something figured out. Creating a "key" table works (when the bindings are set correctly).

In other words, e'en though Person & Hat have a many-to-many relationship, it APPEARS that CoreData can't directly support that. The developer must put a key table between to hold the relationships. Thus, an entity called Person_Hat needs to exist that has to-one relationships with Person & Hat, which are the inverse of the to-many relationships from Person & Hat. I got that functional this morning.

Though Apple dox clearly show many-to-many relationships as a possibility, a strict many-to-many isn't necessarily supported.

I'm still waiting to hear back from the list as to any particular reason why that doesn't/cant work.

Thanks again for any assistance.

Peace, Love, and Light

/s/ Jon C. Munson II