[andrewstuart2]

"The case for identifiers" is really more of a case for surrogate keys. Surrogate keys need not be opaque, but rather are distinguished by the fact that they're assigned by an authority and may be completely unrelated to the properties of an entity.

Natural keys, meaning entity identification by some unique combination of properties, are hard to get right (oops, your email address isn't unique, or it's a mailing list) and a pain to translate into a name (`where x = x' and y = y' and z = z'`, or `/x/x'/y/y'/z/z'`, etc.).

Surrogate keys, on the other hand, make it easy to identify one and only one object forever, but only so long as everybody uses the same key for the same thing.

And as mentioned in the article, the most appropriate is usually both. Often you don't have the surrogate key, so you need to look up by the natural key, but when you do have the surrogate key, it's fastest and most likely to be correct if you use that in your naming scheme.