URN validity as a valid URL string

[pzb]

What is the issue with the URL Standard?

In the examples table in section 4, urn:isbn:9780307476463 is listed as a valid URL string. At first glance, it seems to be a absolute-URL string, but appears to fail because:

• urn is a URL-scheme string that is not a special scheme, therefore must be followed by a relative-URL string
• isbn:9780307476463 does not start with / so it cannot be a scheme-relative-URL string or path-absolute-URL string
• leaving the only the path-relative-scheme-less-URL string for relative-URL string , but
• isbn:9780307476463 fails the test of "does not start with: a URL-scheme string, followed by U+003A (:)"

How is the URN string a valid URL string if it doesn't have a valid relative-URL string?

The term "opaque path" is used in various places in the spec, but does is not used in the definition of valid URL string. One solution might be to better define "opaque path" and use it in the definition.

[domenic]

• the test of "does not start with: a URL-scheme string, followed by U+003A (:)"

This test applies to 9780307476463, not the whole URL.

Remember that the sub-definition of "absolute-URL string" that you're looking at is:

a URL-scheme string that is not an ASCII case-insensitive match for a special scheme, followed by U+003A (:) and a relative-URL string

So we've already accounted for isbn:, and now we're looking at whether what remains (9780307476463) matches "relative-URL string".

I'll close this since I'm pretty sure the spec is fine here, but happy to continue discussing and reopen if I've missed something.

[pzb]

The full URL is urn:isbn:9780307476463. The scheme is urn and the relative-URL string is isbn:9780307476463. isbn is not a scheme.

Another example URL is arn:aws:ec2:us-east-1:4575734578134:instance/i-054dsfg34gdsfg38. The scheme is arn and the relative-URL string is aws:ec2:us-east-1:4575734578134:instance/i-054dsfg34gdsfg38. aws is not a scheme in this context.

Both of these URLs use opaque paths, but it appears that URL Writing does not account for opaque paths. The URL parsing section of the spec does account for opaque paths.

[annevk]

1. a URL-scheme string that is not an ASCII case-insensitive match for a special scheme, followed by U+003A (:) and a relative-URL string
2. a path-relative-scheme-less-URL string