ср, 8 июн. 2022 г., 03:07 Gavin Lambert via Boost
The parsing-level distinction between the two is generically obvious and does not require recognition of the specific scheme; if the scheme colon is immediately followed by one or more slashes then it's an URL, otherwise it is not. But this is off-topic.
This is wrong, there's absolutely no syntactic distinction between URIs and URLs. The distinction is in their purpose. Consult this section: https://datatracker.ietf.org/doc/html/rfc3986#section-1.1.3 The two slashes mean that URI contains the authority part. One slash means it doesn't. What it means for the URI is essentially decided by the scheme or the application authors.
And on the other hand, http scheme is usually associated with the
idea of URL. But e.g. XML namespaces are identified by URIs, often those are http URIs, and there's absolutely no guarantee that the URI can be used to retrieve some document from the Internet.
They're still URLs, regardless of whether they resolve to a valid web resource or not. (They're also URIs, of course.)
How could they be URLs, when they aren't supposed to be used to Locate anything, and the defining characteristic of being a URL is that it describes how to get the thing?