I don't think we should give up on the idea of reusing Locations so quickly. Assuming we go with Locations as SDOs, it certainly is a problem if you reuse someone's Location and they change it from underneath you. I was first thinking that there should be immutable SDOs - in other words, the unique USA Location SDO CAN'T be changed. If we had a set of the common ones (defined in some library/repo somewhere) then we could just use their ids. Duplicates are allowed, but hopefully few people would need to create their own USA Location SDO. I was thinking of an extra property (on all SDOs?) - final. If final is true for an SDO, then a new version couldn’t be created.
Adding immutable objects to the spec might be a good idea in general, but I think a simpler way to handle this is just to "trust" that the library/repo contains objects that will not change. In other words, locations created by a certain (well-known) identity (SDO-Immutable-Library) could be reused with little concern that they are going to change. And if they DO change - maybe that is a feature - after all, all those Soviet-Union Location SDOs are no longer too useful...
