Re: [Uri-review] Request for review

[Graham Klyne <[e-mail]>]

Hi Tim,

A short answer here is that you need the colon after the scheme name because 
that's what the URI specification, which represents a community consensus, says.

A pragmatic response is that many contexts allow either a URI or a relative 
reference to be used (e.g. HTML <a href="...">).  So it's important for a 
processor to be able to distinguish between these cases.  The colon after the 
sceme name is what makes that possible 
(https://tools.ietf.org/html/rfc3986#section-4.1).

(BTW, I wasn't suggesting you were treating anything as arbitrary.  But in 
practice, some choices *are* arbitrary, and for interoperability we need to 
agree some such choices.)

#g
--


On 29/05/2020 17:45, Timothy Mcsweeney wrote:
> Hi Graham,
> 
> I would never treat suggestions from this list as arbitrary, quite the contrary.
> I want to change the format of this reply just for a minute to express my 
> deductions.
> 
> This is an excerpt from the conversation in my head:
> 
> 
> If you take away all the components and subcomponents of a URI, what's leftover?
> The colon.
> And what governs the colon?
> The dereferencing algorithm.
> Does http use a colon in its dereferencing?
> It does.
> What about a URN?
> It does.
> FTP and Mailto?
> Yup the same.
> So If you change the colon to a number sign would you get them same output?
> Yes.
> All of them?
> Yes.
> Can you prove it?
> Yes.
> Why do all the delimiters have quotes around them?
> Because they are interchangeable.
> Interchangeable everywhere?
> No, just within the scope of their placement.  That's why URNs can use a bunch 
> of colons and not interfere with the first colon after the URN scheme name.
> But it says the colon is required doesn't it?
> I can not pinpoint the sentence that says that.
> But section 3, the colon is in the generic syntax, you can see that right?
> Yes but the title of section 3 is "Syntax Components" and the colon is not a 
> component.
> Wait, what does generic mean?
> Not specific.
> So the generic syntax is not specific?
> That's right.
> So [RFC3986] is a specification that is defining something that is not specific?
> Yup, says it right there in the abstract.
> 
>  From here my mental conversation took a left turn.  But I wanted to put this 
> out here so that the members of this list didn't think my intent was for purely 
> self interest reasons but that we can all use what's here.
> Tim
> 
>> On May 29, 2020 at 6:01 AM Graham Klyne < [e-mail] 
>> <mailto:[e-mail]>> wrote:
>>
>>
>> Hmmm... I find that bit of RFC3986 isn't immeditely clear. But on closer study,
>> I think it's simply saying that the characters are "safe" in the sense that
>> they are protected from change by URI normalization, hence that when used as
>> delimiters there is no risk that the interpretation of the URI is affected by
>> URI normalization (see also section 6 of RFC 3986).
>>
>> But some of these reserved characters already have defined purposes in URI
>> structure, and any scheme-dependent use needs to take care not to interfere with
>> such use. For example, using "#" as a delimiter within a URI path would
>> interfere with it's already-defined purpose to delimit a fragment.
>>
>> Also, current URI structure *requires* that the ":" is used to delimit the
>> scheme name from the rest of the URI. Suggestions by others on this list to use
>> ":" rather than "#" are not entirely arbitrary.
>>
>> As a rule of thumb, I would suggest that if you do need scheme-specific
>> delimiters (and it's not clear to me that you do), then using one from the
>> "sub-delims" set is more likely to avoid conflicts with generic URI syntax and
>> interpretation.
>>
>> #g
>> -- 
>>
>>
>> On 28/05/2020 02:06, Timothy Mcsweeney wrote:
>>> Hi Dave,
>>>
>>> By "safe" I meant like ".....
>>>
>>> safe to be
>>> used by scheme-specific and producer-specific algorithms for
>>> delimiting data subcomponents within a URI"
>>>
>>> Like it says in section 2.2 of RFC3986.
>>>
>>> Tim
>>>
>>>> On May 27, 2020 at 8:48 PM Dave Thaler < [e-mail] 
>>>> <mailto:[e-mail]>> wrote:
>> >> s/URL/URI/ in both cases in my response J
>> >>
>> >> *From:*Uri-review < [e-mail] 
>> <mailto:[e-mail]>> *On Behalf Of *Dave Thaler
>> >> *Sent:* Wednesday, May 27, 2020 5:47 PM
>> >> *To:* Timothy Mcsweeney < [e-mail] <mailto:[e-mail]>>; 
>> [e-mail] <mailto:[e-mail]>
>> >> *Subject:* Re: [Uri-review] Request for review
>> >>
>> >>
>> >> I don’t understand your question.   The URL syntax is fixed by that RFC.
>> >>
>> >> I don’t know what you mean by “safe” or “valid”.
>> >>
>> >> If by “valid” you mean “allowed by RFC 3986”, the answer is that they may only
>> >> appear in a URL literally
>> >>
>> >> if they have the exact meaning in the RFC, otherwise they must be pct-encoded.
>> >>
>> >> *From:*Uri-review < [e-mail] 
>> <mailto:[e-mail]>
>> >> <mailto: [e-mail] <mailto:[e-mail]>>> 
>> *On Behalf Of *Timothy Mcsweeney
>> >> *Sent:* Wednesday, May 27, 2020 5:05 PM
>> >> *To:* [e-mail] <mailto:[e-mail]> <mailto: 
>> [e-mail] <mailto:[e-mail]>>
>> >> *Subject:* Re: [Uri-review] Request for review
>> >>
>> >>
>> >> Hi Dave,
>> >>
>> >>
>> >> If the other six gen-delims from the reserved set were safe and valid, would
>> >> you oppose their use in URIs?
>> >>
>> >>
>> >> Tim
>> >>
>> >>
>> >>
>> >>
>> >> On May 24, 2020 at 6:08 PM Dave Thaler < [e-mail] 
>> <mailto:[e-mail]>
>> >> <mailto: [e-mail] <mailto:[e-mail]>>> wrote:
>> >>
>> >> Hi Tim,
>> >>
>> >> Correct the colon is not part of the hier-part, the hier-part is what
>> >> comes after the colon.  RFC 3986 says:
>> >>
>> >> URI         = scheme ":" hier-part [ "?" query ] [ "#" fragment ]
>> >>
>> >> Only strings that conform to the above are URIs.
>> >>
>> >> So “drop#sd54g54” is not a URI because it does not conform to the above
>> >> syntax, as it has no “:”
>> >>
>> >> “drop:sd54g54” on the other hand would be a valid URI.
>> >>
>> >> This is what folks are saying when they say if you just change the “#” to
>> >> a “:” in your draft then it becomes legal.
>> >>
>> >> Dave
>> >>
>> >> *From:*Uri-review < [e-mail] 
>> <mailto:[e-mail]>
>> >> <mailto: [e-mail] <mailto:[e-mail]>>> 
>> *On Behalf Of *Timothy Mcsweeney
>> >> *Sent:* Sunday, May 24, 2020 11:26 AM
>> >> *To:* Erik Wilde < [e-mail] <mailto:[e-mail]> 
>> <mailto: [e-mail] <mailto:[e-mail]>>>;
>> >> [e-mail] <mailto:[e-mail]> <mailto: 
>> [e-mail] <mailto:[e-mail]>>
>> >> *Subject:* Re: [Uri-review] Request for review
>> >>
>> >>
>> >> Hi Erik,
>> >>
>> >>
>> >> Thank you, I will have another look at my reference to section 3.
>> >>
>> >> Would you agree that in " https://ietf.org
>> >> < "" rel="noopener" 
>> target="_blank">https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fietf.org%2F&data=02%7C01%7Cdthaler%40microsoft.com%7Cb115c7f8c70b410eb98308d802a0a8f4%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637262236339204192&sdata=UJ7TQnKfGZMnWkBKZCVozZQhn%2BGir1saiPQoNGV2C9M%3D&reserved=0>" 
>>
>> >> the colon is not part of the hier-part?
>> >>
>> >> On May 24, 2020 at 12:02 PM Erik Wilde < [e-mail] 
>> <mailto:[e-mail]>
>> >> <mailto: [e-mail] <mailto:[e-mail]>>> wrote:
>> >>
>> >>
>> >>
>> >> hey tim.
>> >>
>> >>
>> >> On 2020-05-24 17:53, Timothy Mcsweeney wrote:
>> >>
>> >> Yes, I agree and understand that the same way as you.   But when
>> >> the "#"
>> >>
>> >> leaves the client it is not leaving as a fragment,
>> >>
>> >> what people are telling you is that "#" and anything following it never
>> >>
>> >> leaves the client, by definition..
>> >>
>> >>
>> >> it is leaving as a
>> >>
>> >> way to separate the URI components, <scheme> and <path> or for http it
>> >>
>> >> would be separating <scheme> and <authority>.  It is this that
>> >> makes me
>> >>
>> >> believe that even if the colon is required for http resolution, it is
>> >>
>> >> not necessarily required for all URI.
>> >>
>> >> this discussion could be more productive if you had a brief look at the
>> >>
>> >> specs you're depending on. the very first rule shown in
>> >>
>> >> https://tools.ietf.org/html/rfc3986#section-3
>> >> < 
>> https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Ftools.ietf..org%2Fhtml%2Frfc3986%23section-3&data=02%7C01%7Cdthaler%40microsoft.com%7Cb115c7f8c70b410eb98308d802a0a8f4%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637262236339214150&sdata=upZbOkALJ8SuEk%2FpLLqhdDDUNMhdpSmjWqpMAyITzc8%3D&reserved=0> 
>>
>> >> is
>> >>
>> >>
>> >> URI = scheme ":" hier-part [ "?" query ] [ "#" fragment ]
>> >>
>> >>
>> >> each URI is defined like this and must have a colon.
>> >>
>> >>
>> >> cheers,
>> >>
>> >>
>> >> dret.
>> >>
>> >>
>> >> --
>> >>
>> >> erik wilde | mailto: [e-mail] <mailto:[e-mail]> 
>> <mailto: [e-mail] <mailto:[e-mail]>> |
>> >>
>> >> | http://dret.net/netdret
>> >> < 
>> https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fdret.net%2Fnetdret&data=02%7C01%7Cdthaler%40microsoft.com%7Cb115c7f8c70b410eb98308d802a0a8f4%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637262236339214150&sdata=hq8QVDrXxRmV3iS6DF7R%2FeXFtDKntMcYOHnLSMqx5zo%3D&reserved=0> 
>>
>> >> |
>> >>
>> >> | http://twitter.com/dret
>> >> < 
>> https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Ftwitter.com%2Fdret&data=02%7C01%7Cdthaler%40microsoft.com%7Cb115c7f8c70b410eb98308d802a0a8f4%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637262236339224105&sdata=9V5l2cgygLF2GJbT9Eh0ptd2mv4YRbvZm6oaYSrf8fE%3D&reserved=0> 
>>
>> >> |
>> >>
>> >>
>>>
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