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Comment by IshKebab | Hacker News Reader

Why even are they URLs? The only reasonable suggestion I could find is that it was part of an abandoned or poorly adopted idea to also host the schema at that URL.

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Probably the same sort of thought process that led to the convention of Java packages being named com.example.whatever. It identifies the creator and gives you some structure to create a unique identifier.

Lot of half-baked ideas floating around in the early years of the commercial internet, but the Java thing held up better.

It's a way to ensure global uniqueness. In the end they're just compared byte-for-byte as strings.

Precisely, so why are they URLs and not something like Java's packages? Or just a URL without the `http://`?

Snarky answer: because they're the W3C and are high on their own supply ;-)

But it does allow more flexibility. If you don't want to be tied to a domain name, you can use a URN with a UUID like urn:uuid:4603d9d3-e895-4000-9077-0ab0f2776e1e

You could also just do `com.mydomain.uid.4603d....` if you wanted. But yeah I think your snarky answer is probably more than a little true!

In addition to the uniqueness others have mentioned, where do you find the canonical definition of the schema if it doesn’t have a url? So they just cut out the mapping and made them one.

This is nonsensical. Where did you get the XSD from? You could get a proper spec from the same place. Contrast this with JSON, which makes zero attempt. People (generally) prefer that. If you were dead-set on embedding the documentation URL in the namespace, you could at least remove the tripping hazard and use new "protocol" like `xsd-spec://host/specs/foo/v1.2` or something.

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