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Guidelines on usage of // in new URI schemes

From: Eran Hammer-Lahav <eran@hueniverse.com>
Date: Wed, 19 Aug 2009 22:48:22 -0700
To: "apps-discuss@ietf.org" <apps-discuss@ietf.org>, URI <uri@w3.org>
Message-ID: <90C41DD21FB7C64BB94121FBBC2E72343783606CBD@P3PW5EX1MB01.EX1.SECURESERVER.NET>
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
Received on Thursday, 20 August 2009 05:49:01 GMT

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