[DFDL-WG] Fw: date & time and latest ICU possible issues/conflicts

Tue Jan 22 11:08:13 EST 2013

I would agree that DFDL should drop the single 'V' character since they're
dropping it from ICU.

On Mon, Jan 21, 2013 at 1:23 PM, Steve Hanson <smh at uk.ibm.com> wrote:

> Clarification from CLDR via ICU on the* single 'V' re-use* issue:
>
> *"V" was originally designed for a variant of pattern "z" in CLDR. It had
> a valid reason to define a pattern different from "z", but we found that
> CLDR cannot collect such information differentiating "V" from "z". Also,
> there were no users who requested us (including ICU) to maintain proper
> data for differentiating "V" from "z". As the result, the data making the
> difference between "V" and "z" was deprecated, and we no longer have reason
> to keep pattern "V" except backward compatibility reason.*
>
> *So, strictly speaking, it's a backward compatibility problem. But -*
>
>    - *It still produces a text representation of the same calendar field.
>    *
>    - *"V" was not adopted by any other known implementations other than
>    ICU. *
>    - *The distinction between "V" and "z" had never worked as users would
>    expect. *
>    - *"z" is a Java compatible pattern for short abbreviated zone format,
>    and it is available from the very beginning. On the other hand, "V" was a
>    recent addition. *
>
> *CLDR technical committee including myself understand the risk, but all
> of us preferred cleaner pattern definition over the potential backward
> compatibility problem.**
> *
>
> Sound like DFDL should withdraw 'V', I doubt that any IBM customer will be
> using it. 'VVVV' is ok.
>
> Regards
>
> Steve Hanson
> Architect, Data Format Description Language (DFDL)
> Co-Chair, *OGF DFDL Working Group* <http://www.ogf.org/dfdl/>
> IBM SWG, Hursley, UK*
> **smh at uk.ibm.com* <smh at uk.ibm.com>
> tel:+44-1962-815848
> ----- Forwarded by Steve Hanson/UK/IBM on 21/01/2013 18:17 -----
>
> From:        Steve Hanson/UK/IBM
> To:        dfdl-wg at ogf.org,
> Date:        17/01/2013 10:04
> Subject:        Fw: [DFDL-WG] date & time and latest ICU possible
> issues/conflicts
> ------------------------------
>
>
> The ICU ticket has been answered, with reference to the following
> document:
>
> http://cldr.unicode.org/development/development-process/design-proposals/time-zone-offset-patterns
>
> *'x'/'X' symbols*
> In a not-too-distant ICU there will be new symbols 'x' and 'X' to handle Z
> as a time zone for ISO8601 date/times, effectively replacing 'ZZZZZ'. Both
> 'x' and 'X' will tolerate Z or +00:00 (or variants) on parsing, and on
> formatting X will result in Z and x will result in +00:00 (or variants).
>
> DFDL's use of 'U' is wider than this, as we allow 'U' to appear with any
> number of 'Z's, meaning that Z is accepted with non-ISO8601 date/times.
> DFDL also adds the use of 'I' symbol on its own to mean any ISO8601
> compliant date/time, and again we allow 'U' to appear with 'I'.
>
> However the motivating use case for adding 'U' was IBM MRM which supports
> this today. But it does so primarily for XML use cases, in particular
> ISO8601. I am not personally aware of an actual non-XML use case.
>
> I suggest we drop the DFDL-specific use of the 'U' symbol in conjunction
> with 'Z' and 'I' symbols from the DFDL specification via errata, and allow
> the use of 'ZZZZZ' instead, which at least will accept Z when parsing. When
> 'x'/'X' support appears in ICU, we can take a future errata to support it
> or leave until DFDL 2.0.
>
> IBM DFDL already supports 'U' but I am ok with deprecating it as I don't
> believe it will be being used for real.
>
> *'V' symbol*
> In a not-too-distant ICU there will be new symbols 'VV' and 'VVV' to
> handle time zones expressed as Time Zone Ids and localized locations,
> respectively. We can add that via errata in the future, or leave until DFDL
> 2.0.
>
> However, at the same time the meaning of V is changed slightly. DFDL
> supports 'V'. I have asked ICU for a clarification.
>
> *'O' symbol*
> In a not-too-distant ICU there will be new symbol 'O' to handle localized
> GMT format variants. We can add that via errata in the future, or leave
> until DFDL 2.0.
>
> Regards
>
> Steve Hanson
> Architect, Data Format Description Language (DFDL)
> Co-Chair, *OGF DFDL Working Group* <http://www.ogf.org/dfdl/>
> IBM SWG, Hursley, UK*
> **smh at uk.ibm.com* <smh at uk.ibm.com>
> tel:+44-1962-815848
> ----- Forwarded by Steve Hanson/UK/IBM on 17/01/2013 08:58 -----
>
> From:        Steve Hanson/UK/IBM
> To:        Mike Beckerle <mbeckerle.dfdl at gmail.com>,
> Cc:        dfdl-wg at ogf.org
> Date:        16/01/2013 18:20
> Subject:        Re: [DFDL-WG] date & time and latest ICU possible
> issues/conflicts
> ------------------------------
>
>
> ICU ticket raised as the help does not give an example.
>
> https://icu.sanjose.ibm.com/gcoctrac/ticket/469#ticket
>
> Regards
>
> Steve Hanson
> Architect, Data Format Description Language (DFDL)
> Co-Chair, *OGF DFDL Working Group* <http://www.ogf.org/dfdl/>
> IBM SWG, Hursley, UK*
> **smh at uk.ibm.com* <smh at uk.ibm.com>
> tel:+44-1962-815848
>
>
>
> From:        Mike Beckerle <mbeckerle.dfdl at gmail.com>
> To:        dfdl-wg at ogf.org,
> Date:        16/01/2013 15:11
> Subject:        [DFDL-WG] date & time and latest ICU possible
> issues/conflicts
> Sent by:        dfdl-wg-bounces at ogf.org
> ------------------------------
>
>
>
>
> Steve Lawrence is on the Daffodil Open Source DFDL team (on CC), and he
> has dug into date/time types.
>
> He raised some concerns to me that I really haven't been tracking at all,
> so I wanted to put in front of the rest of the group.
>
> The date time format syntax for the latest version of icu4j contains a 'U'
> character, which means "cyclic year name". However, the daffodil
> spec says the 'U' character, following a Z makes it so a timezone of UTC
> is represented as Z instead of +00:00.
>
> This seems to be a conflict, and would prevent us from ever upgrading to
> the newest version of ICU (which might be a good idea).
>
> I will point out that the latest version of ICU supports ZZZZZ (5 Z's),
> which is the ISO8601 timezone format. This doesn't add all the
> functionality that the DFDL 'U' gives. My question is, is this enough?
> Are there cases where the ZU, ZZU, etc. are necessary? I'm just
> concerned that the U is going to quite a bit more complexity, and want
> to make sure the updates to latest ICU don't address the DFDL-WG concerns.
>
> And if we still need the 'U', maybe it should change to a different
> letter to prevent conflicts with the latest ICU4J?
>
> I would point out that the ICU pattern language cannot deal with
> dual-purpose letters very well, i.e., ambiguities are introduced if the
> same letter both introduces a format, and if following another format
> string, modifies its behavior. E.g., does ZU mean Z modified by U, or Z
> first, and then U. So it seems pretty unfortunate if the ICU libraries
> added a conflicting use of letter U.
>
> I believe the point of DFDL's use of the U modifier for letters I and Z
> was to be absolutely clear on the GMT timezone 'Z' issue, i.e., to indicate
> that 'Z' is to be used, and -00:00 is not to be output, nor accepted when
> parsing. The ICU specification ZZZZZ says ISO format, but that allows
> either 'Z' or -00:00 to be used for GMT timezone, and it's not clear what
> it means on output.
>
> --
> Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | *
> www.tresys.com* <http://www.tresys.com/>
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>
> Unless stated otherwise above:
> IBM United Kingdom Limited - Registered in England and Wales with number
> 741598.
> Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
>
> Unless stated otherwise above:
> IBM United Kingdom Limited - Registered in England and Wales with number
> 741598.
> Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
>
>
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>   dfdl-wg mailing list
>   dfdl-wg at ogf.org
>   https://www.ogf.org/mailman/listinfo/dfdl-wg
>

-- 
Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology |
www.tresys.com
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