Re: Guidelines on usage of // in new URI schemes

*Hello*

See RFC 2718 - Guidelines for new URL Schemes
http://www.ietf.org/rfc/rfc2718.txt

2.1.2 Improper use of "//" following "<scheme>:"

Contrary to some examples set in past years, the use of double
slashes as the first component of the <scheme-specific-part> of a URL
is not simply an artistic indicator that what follows is a URL:
Double slashes are used ONLY when the syntax of the URL's <scheme-
specific-part> contains a hierarchical structure as described in RFC
2396. In URLs from such schemes, the use of double slashes indicates
that what follows is the top hierarchical element for a naming
authority. (See section 3 of RFC 2396 for more details.) URL
schemes which do not contain a conformant hierarchical structure in
their <scheme-specific-part> should not use double slashes following
the "<scheme>:" string.


On Thu, Aug 20, 2009 at 8:48 AM, Eran Hammer-Lahav <eran@hueniverse.com>wrote:

> I am in the process of proposing a new URI scheme to identify user accounts
> [1]. This is part of the WebFinger protocol [2] effort.
>
> This email is *not* an invitation to debate the merits of this new URI
> scheme (just yet). I am sure we will have many lively discussions about it
> shortly but I would like to present a proposal before we have a public
> debate about it here.
>
> The new scheme has two components, a local identifier (username,
> screenname, handle, etc.) and a host (which can resolve and authenticate the
> local identifier). When looking at the URI specification (RFC 3986) and at
> the new URI guidelines (BCP 35), it is hard to figure out what is an
> appropriate use of // in new schemes.
>
> In this case, we have a requirement to keep the URI (the part after the
> scheme:) looking as close to an RFC-822 identifier (username@host) and
> that means two options:
>
> acct:username@host
> acct://username@host
>
> The 'username@host' part seems to fit perfectly into the URI authority as
> defined by RFC 3986. However, since the URI does not have a path, it does
> not really contain a hierarchical structure (just the top level host).
>
> The benefit of using // in this case is that existing URI parsing code can
> be used unmodified to process the new URI. It is a simple profile which only
> allows the userinfo and host subcomponents of the authority component, and
> no other URI components. Since the new scheme will be often used with URI
> templates and other facilities often used with http: URIs, it is very
> convenient to have a common structure (even if it is only a subset). I don't
> see any down side to using // other than defying expectations established by
> the mailto: URI scheme.
>
> The benefit of not using // is that it makes the URI follow the well
> establish pattern in mailto: and save two bytes. The down side is that it
> requires spelling out how to break the URI path into sub components specific
> to this scheme.
>
> So far the feedback I received is focus on style which is perfectly valid,
> but I want to make sure I am not missing anything. My preference is to reuse
> as much as possible and therefore include the //.
>
> Any suggestions?
>
> EHL
>
> [1]
> http://www.hueniverse.com/hueniverse/2009/08/making-the-case-for-a-new-acct-uri-scheme-for-accounts.html
> [2] http://code.google.com/p/webfinger
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