Re: [apps-discuss] The acct: scheme question

Graham Klyne <> Tue, 22 May 2012 15:24 UTC

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Date: Tue, 22 May 2012 16:22:54 +0100
From: Graham Klyne <>
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Subject: Re: [apps-discuss] The acct: scheme question
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On 22/05/2012 14:57, Paul E. Jones wrote:
> The debate over the "acct" URI scheme still seems to be centered on the
> argument that we either do not need a URI scheme at all or we can re-use an
> existing scheme.  I am very much opposed to a scheme-less solution, since
> RFC 6415, link relations, and Web-Linking, HTML, and all related work upon
> which WebFinger depends relies on URIs.  The URI is what is used to
> differentiate one type of entity from another.  A query for "mailto:", for
> example, might return information about one's mail servers, mail accounts
> (e.g., POP or IMAP configuration information), etc.  A query for "xmpp:"
> might return information about one's XMPP server, buddy list, etc.  A query
> for "sip:" might return information about a user's SIP registrar, outbound
> SIP proxy, or other configuration information.
> Of course, one could build a WebFinger server to return everything about a
> user regardless of the URI scheme.  I just think that is an inappropriate
> way to respond to a WebFinger query.  The "acct" URI was intended to be the
> single URI scheme that would return information about a person (or possibly
> a thing) that holds an account at a given domain.  It would be the one URI
> scheme that would return information like vcards, OpenID identifiers,
> references to social networking pages, photo sharing resources, etc.  It
> might also return other URIs like""  or
> "", which is information about me and ways to
> contact me.

It's a clever idea to use the URI scheme to get information about different 
kinds of account.  But I find myself deeply uneasy about it, though not yet 
entirely sure why...

Maybe it's because it seems to violate the Web architectural principle of URI 

OTOH, it seems quite reasonable to me that (say) one might use
to reference information about different kinds of account.  They're just 
different URIs referencing different stuff.  So why not the same for different 
scheme names?

Unlike a path component in an HTTP URI, a scheme name comes with some quite deep 
wired-in semantics: administrative, technical or both.  What assurances do we 
have that the webfinger use of the scheme name will not end up conflicting with 
the scheme's own semantics?  If the URI is a simply a name for routing a request 
for information, and nothing more, which is what seems to be the case when 
looking at, then the case for having 
a special URI scheme acct: appears to be rather weak - it seems to me that a URN 
namespace, or any other form of URI created to refer to a users personal 
information would serve just as well.

If, on the other hand, webfinger makes additional operational, administrative or 
technical associations with an acct: URI, the whole idea of using an arbitrary 
scheme name for accessing different information seems to be dangerous, as the 
scheme has been loaded with additional semantics that might conceivably conflict 
with semantics of existing schemes.


(For the avoidance of doubt: these comments are made in a purely personal capacity.)