Re: telephone URLs, comments on draft-antti-telephony-url-04

Roy T. Fielding (fielding@kiwi.ics.uci.edu)
Sat, 27 Jun 1998 01:39:47 -0700


To: "Vaha-Sipila Antti (NMP)" <antti.vaha-sipila@nmp.nokia.com>
cc: URI distribution list <uri@Bunyip.Com>
In-reply-to: Your message of "Fri, 26 Jun 1998 14:17:27 +0200."
             <355C4C5517A5D111A25800805FEA72A115C491@nmpies02tr.nmp.nokia.com> 
Date: Sat, 27 Jun 1998 01:39:47 -0700
From: "Roy T. Fielding" <fielding@kiwi.ics.uci.edu>
Message-ID:  <9806270139.aa11280@paris.ics.uci.edu>
Subject: Re: telephone URLs, comments on draft-antti-telephony-url-04 

>This is true. Unfortunately, not all phone numbers are accessible using
>a global numbering scheme. Such a case might be a freephone number which
>is only accessible from a certain country; numbers under a company PBX;
>network specific numbers (my mobile phone operator uses a three-number
>code to access my voice mailbox), etc.

You can do that with a notation for local-only within the URI.
You don't need a separate scheme for that.

>> A URL is a Uniform Resource Locator, and "uniform" means that a
>> URL should identify the same resource no matter where it is accessed.
>
>Yes, but doesn't the "locator" mean that information about the method of
>getting to that location should also be present? URNs (uniform resource
>names) are used it does not matter where the resource is accessed. Or
>have I mixed up the terminology?

A locator means it can be used to locate a resource.  It does not mean
the string contains location information.  For example, the http URL
defines names according to the naming authority of a particular server.
This does not mean you need to access that server in order to retrieve
a representation of that resource.  All that is needed is for the resource
namespace to be defined such that the client can determine a mechanism
for locating the resource.

There is only one naming authority (partitioned into sub-authorities)
for the entire telephone namespace.  Therefore, it makes sense to only
have one URL scheme for phone names.  The action to take (fax, talk,
etc.) should be independent of the URI.

>However, in this case, there might not be a "base" at all, since phone
>numbers may indeed be dialable only from inside a certain network or a
>branch exchange. Again, consider the special access number I have for my
>voice mailbox: whenever I dial XXX from my mobile, I get there, but I
>cannot do that from another phone, not even from another network than my
>home network, no matter what I dialled.
>
>In other words, phone numbers do not translate well into a hierarchical
>structure.

On the contrary.  What you described is a phone number with a
null national/regional context.  So define a representation of such
and put it in place of the national/regional context.

Phone numbers are a hierarchical structure.  You can tell that by the
way they are abbreviated in context.

>> I would like to (re)consider whether separate schemes for
>> 'tel', 'fax' and 'modem' should be used, rather than having
>> the 'call style' be a parameter, if such is necessary.
>> The URL uniformly locates the resource, and doesn't need to
>> specify the service that is to be obtained at that resource.
>
>HTTP and FTP URLs both locate a resource - a file. Implicitly they also
>specify which kind of connection has to be made to retrieve that file
>(which protocol to use).

Sorry, but that is completely wrong.  This is explained in the introduction
to the URI syntax spec.

....Roy