The Rhodo monographs are explained in this blog post.

I am with you on the notion that without proper resolver/locator using UUIDs is dangerous (as any other identifier).

Identifier to me is a unique ‘handle’ to one ‘thing’. Global identifier is a globally unique handle to one thing. Your example describes a usage of a global identifier, when two agents by ignorance of malevolence assign one handle to 2 different things. Such identifier stops to be a global identifier by definition. It still works fine as a local one. Situations like these can be resolved as you say by the appropriate resolver/locator.

What makes one thing to be ‘one thing’ is another story and is probably included in the wisdom of the food resolver.

UUIDs in my understanding allow someone to mint an identifier for their chocolate cake and then submit it to a locator, being pretty sure that there is no such UUID assigned to anything. If someone picks a created UUID for spicy pizza and submits it attached to a chocolate cake to a global food resolver, they won’t succeed. If they make their own UUID for spicy pizza, they can be quite sure their registration will come through without consulting food resolver beforehand.

UUID5s allow creation of exactly the same UUID in the same name space for the same text string by anyone using any popular modern programming language as long as they know the algorithm. It opens interesting opportunities and makes pizza/cake situation impossible.

For my projects I am nervous to use locators as identifiers. I remember time when there were no urls. There is no guaranty, that urls ability to resolve will persist in the future. Numbers on the other hand are used throughout whole human existence and don’t carry an overhead/ambiguity/inconsistency/semantic load of urls. A UUID is nothing but a 128bit number so I like to use it for identifying things. I also think it is silly to stop there and not use adequate resolvers of some kind, as you point in the post.

Saying all that, if something still escapes my understanding, sorry for my limitations, I’d like to try to wrap my head around it.

Dima

Thanks for you comment.

Not sure what you mean by ‘identify’ in this context. If I say 550e8400-e29b-41d4-a716-446655441234 stands for spicy pizza and you say it is chocolate gateaux then nobody else in the world can know what that particular UUID stands for. It stands for at least two things and possibly more. They don’t know whether to order it for first course of second course.

For me identity only makes sense within a particular context – with a particular issuing authority. An identity card I create myself doesn’t count for much but one issued by the state does. On the internet we have a perfectly good hierarchically managed system of authority for issuing identifiers called the DNS system. It is the singularity of the authority system that makes the identifiers valuable. As soon as you say there are multiple ways to ‘get’ to an object then the identifier no longer identifiers a single thing. It’s just namespaces really.

Anyhow this is making me hungry!

Roger

UUID is an identifier, and a good one. It is not a locator at all. The issues you mention appear when people try to use identifier without a proper locator mechanism. In case of UUIDs people would need to agree what locator to use.

The great thing about UUIDs — you do not mix two separate tasks together, they are ONLY identifiers, and nothing else. To be useful they have to be resolved by a locator, whatever it will be at the moment or circumstance LSID, PURL, a local database API… However when locator gets outdated it is easy to migrate to the next and great one.

UUID5 also creates an opportunity to have a distributed ‘minting’ service for uuids where a textual information needs a 1 to 1 unique identifier (which works well for example for name strings).

It is interesting that you conflate purpose and meaning. I think of purpose as being something that can be described in words. “We did it because . . .” where as meaning implies something ineffable that may or may not be fully expressible in words – hence poetry and the arts. So life might have a meaning but not a purpose and we may be at a loss to express what that meaning is. Ultimately any ‘notion’ is just that – something that we make up.