Re: Boost.URL -- some notes

From: Gavin Lambert (boost_at_[hidden])
Date: 2022-06-08 23:18:07

On 9/06/2022 08:40, Дмитрий Архипов wrote:
>> 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

Which I did clarify further down.  I know this is the Internet, but you 
don't need to pick every little nit.

> 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.

Containing any leading slashes means that the URI contains a path, which 
means that it represents a location, which automatically makes it an URL 
and not an URN.

As I also said, while it is technically possible for a non-slash-leading 
URI to semantically represent a location and thus also be an URL, this 
is atypical and for most intents and purposes can and should be ignored 
as a useless distinction.  Especially in the context of a generic parser.

> 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?

Any URI that uses the http protocol is (by definition) an URL, because 
it is representing a location.  It does not stop being a location just 
because there is no valid resource at the server claiming to be the 
authority for that location at any particular point in time (or if there 
is no such server); that just makes it an unreachable location.