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Re: Telephone number type

From: C. M. Sperberg-McQueen <cmsmcq@blackmesatech.com>
Date: Tue, 12 Sep 2017 12:38:33 -0600
Cc: "C. M. Sperberg-McQueen" <cmsmcq@blackmesatech.com>, XForms <public-xformsusers@w3.org>
Message-Id: <3A027591-2A0A-4949-94A5-2031B85F3965@blackmesatech.com>
To: Steven Pemberton <Steven.Pemberton@cwi.nl>
On Sep 12, 2017, at 3:43 AM, Steven Pemberton <Steven.Pemberton@cwi.nl> wrote:

> While we're at it, since it is a regularly occurring field in forms,
> how about adding a telephone number type?

> I went looking for suitable standards to reference, and I found
> this:

>	E.123 : Notation for national and international telephone
>	numbers, e-mail addresses and web addresses
>	http://www.itu.int/rec/T-REC-E.123-200102-I/en

> This is actually about how to represent telephone numbers on printed
> materials, but seems usable.

> It doesn't give a formal syntax, only examples and descriptions,
> from which I extract the following syntax:

>  telephone: international | local.
>  international: "+" digits+
>  local: prefix? digits+
>  prefix: "(" digits+ ")"
>  digits: digit (spacing digit)?
>  digit: ["0"-"9"]
>  spacing: " " | "-"

> However, looking at
> ttps://en.wikipedia.org/wiki/National_conventions_for_writing_telephone_numbers
> some countries seem to expect to be able to bracket the area code
> even in an international number,

In some business cards in my collection, parentheses are used not
around an area code but around the country code, sometimes with the
leading "+" inside the parentheses.  A card (from someone in the EU
bureaucracy — which I expect means the pattern is not idiosyncratic to
one individual has:

  (+352) 999 99-99999

Here and elsewhere 9s replace some digits, in the interests of data

Other examples of this pattern (i.e. "(" "+"? country-code ")")
include numbers in the Czech Republic and (with no plus sign) Canada.

  (+420) 999 999 999
  (1) 905 999 9999

Sometimes parentheses are used around a part of the number used in
some cases but not in others.  In all the cases I remember seeing,
it’s a zero between the country code and the in-country number; the
parentheses appear to mean “when calling internationally, omit the
zero, and when calling within the country omit the country code and
include the zero”.  E.g.

   +44 (0) 9999 999999

I think I have seen this most often in German phone numbers, but the
examples in my collection of business cards include ones from the UK,
the Netherlands, and Sweden, as well (and most of my German cards
don't use this pattern, which tells me something but I'm not sure what).

> so we should be a bit laxer; for instance:

>  telephone: prefix? area? digits+
>  prefix: "+" digits+
>  area: "(" digits+ ")"
>  digits: digit (spacing digit)?
>  digit: ["0"-"9"]
>  spacing: " "+ | "-"

> I think this regexp covers it:

> 	"+"? digs+ ("(" digs+ ")" digs+)?

> where:

> 	digs: [0-9] ("-" [0-9])?

> and after every terminal there may follow spaces.

My collection of business cards includes examples with the following
characters used as separators in addition to parentheses, blank, and
  . (i.e. full stop)
  &#183; (i.e. mid-dot)
  “  “ (i.e. two blanks, or extra-wide blank)

I don’t know how important it might be to support such variations.  As
far as I know, they have no well established meaning, although in my
examples / is used only (without white space) between the area code
and the local number and | is sometimes used only (with white space on
either side) between the country code and the in-country number (and
in other cases as the sole separator character)

> That produces this monstrosity:

> <pattern value="^\ *\+?([0-9]\ *(\-\ *[0-9]\ *)?)+(\(([0-9]\ *(\-\ *[0-9]\ *)?)+\)\ *([0-9]\ *(\-\ *[0-9]\ *)?)+)?\ *$"/>

> which you can try out here (scroll to the bottom):


> Let me know if you find cases that don't work.

In addition to the examples given above (some of which work and others
of which don't), some cards in my collection have numbers with the

  800,999.9999 x349
  (1) 905 999 9999 x99999

If extensions are part of a number, these need to work; if not, not.

Also: it appears to be a consequence of the regex that any two hyphens
must be separated by at least two decimal digits.  So the following
Czech number attested in my collection is legal (it appears that '2'
is one of the area codes for Prague)

  +420 (2) 9999 9999

and so is a number with just blanks:

  +420 2 9999 9999
but the following variant is not legal:


I have not seen anything with that last illegal pattern in my
collection, but the other examples in the collection do provide plenty
of examples of (1) separators before and after area codes, (2) use of
whitespace as the only separator, and (3) use of hyphen as the only
separator.  So I am inclined to think it might appear in Real Life.

Do any telephone systems in the world still use lettered exchanges?
The first telephone number I learned as a child began not "366" but
"EM-6" or "Emerson 6".  If that convention is still in use anywhere,
letters will be needed to represent it.

And of course many commercial organizations use numbers that spell out
words; the phone-in number for the quiz show "Whad'Ya Know" (now
defunct), which ran on public radio stations in the U.S. for thirty
years, was 1-800-WHA-KNOW.  Do such numbers need to be supported?

To try to boil it down, the following number patterns are not
supported by the regex given; whether they should be is in each case a
policy question:

  a  (+352) 999 99-99999
  b  999.999.9999
  c  0711/9999-999
  d  613  999-9999 (two blanks or one-em space after area code)
  e +33 | 99 99 99 99  
  f  800,999.9999 x349
  g  (1) 905 999 9999 x99999
  h  +420-2-9999-9999
  i  EM6-9999
  j  1-800-WHA-KNOW

The following number patterns are supported (but use parentheses to
enclose something other than an area code)

  z  (1) 905 999 9999
  y  +44 (0) 9999 999999

Pattern h seems plausible but is not attested in the collection of business cards
I examined; patterns i and j are not attested but specifications of
phone numbers in this form are reasonably well attested (though for
pattern i all the attestations may be decades old by now).

I thank you for an entertaining couple of hours.  (The project leader
to whom I will explain in 45 minutes that I got nothing done on that
project this morning because I was thinking about telephone numbers
may however be less inclined to thank you.  Oh, well.)

C. M. Sperberg-McQueen
Black Mesa Technologies LLC
Received on Tuesday, 12 September 2017 18:39:12 UTC

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