Well, I finally have it working.
I've got several devices and locations that keep calendar, schedule, and contact information. I try to keep things organized, and there are some options for synchronizing one thing to another here and there, some of them third party software, some freeware, and some collaboration suite products. But keeping everything organized and up to date was elusive, and in various attempts to do so I lost all my contact information at least once and various calendar information was either lost or duplicated several times.
Finally, by combining several things in just the right way, I've got it. A major difficulty here is that there's no information-sync equivalent of the Spanning Tree Protocol&emdash;no way for various things to tell when things are being created or deleted in a loop. So one has to be very careful not to create loops, but also to be sure that one-way sync is used in those critical places to avoid two-way information transfer where "hairpin" loops would be created latently.
What I finally came up with is pretty Rube-Goldberg, but does meet all my requirements of preserving the identity of separate calendars across sync, allowing any change to propagate anywhere, operating over the net (and not via docking), and allowing adds/deletes/changes to be made anywhere.