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Fwd: LC-21 non-Gregorian dates

From: C. M. Sperberg-McQueen <cmsmcq@acm.org>
Date: Thu, 05 Oct 2000 23:31:45 -0600
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To: W3C XML Schema Comments list <www-xml-schema-comments@w3.org>
The XML Schema Comments list should have been CC'd on this mail.

>Date: Thu, 05 Oct 2000 20:50:41 -0600
>To: David RR Webber <Gnosis_@compuserve.com>
>From: "C. M. Sperberg-McQueen" <cmsmcq@acm.org>
>Subject: LC-21 non-Gregorian dates
>Dear Mr. Webber:
>The W3C XML Schema Working Group has spent the last several months
>working through the comments received from the public on the last-call
>draft of the XML Schema specification.  We thank you for the comments
>you made on our specification during our last-call comment period, and
>want to make sure you know that all comments received during the
>last-call comment period have been recorded in our last-call issues
>list (http://www.w3.org/2000/05/12-xmlschema-lcissues).
>Among other issues, you raised the point registered as issue LC-21,
>which suggests that XML Schema define, or allow the definition of,
>date types for non-Gregorian calendars.
>We thank you for posing this issue.  In various guises and in
>combination with other issues which proved to be related, it has
>occupied a great deal of our time during the last-call period.
>There is a great deal of sympathy in the WG for providing, in the long
>term, systematic support for non-Gregorian calendars, localized
>notations for common types, and so on.  On this question your
>leanings, the goals of the W3C internationalization WG, and the intent
>of the XML Schema WG are all the same.
>In the short term, however, it proved rather difficult to achieve
>consensus on how best to achieve, or set the stage for later
>achieving, those long-term goals.  The input of the W3C
>internationalization WG was consistently and strongly against allowing
>any value of any simple type to have more than a single lexical form;
>their goal as I understand it is to encourage the development of
>systems with the ability to localize data formats appropriately for
>the particular user they are facing at any given time, and the policy
>of 'sender makes right' is a step toward ensuring that such systems
>are not too difficult to build.
>We are clearly not now in a position to define date types for every
>calendar now in use (let alone those of historical importance which
>might occur in documents to be published on the Web).  For a long
>while, the WG considered a proposal to define a set of 'abstract'
>simple types (e.g. an AbstractDate type) from which schema authors
>could derive localized concrete types (e.g. a Mosaic date in a
>particular format).  In the short term, it would not be feasible to
>provide a way for a schema author to define a mapping between the
>localized form and the canonical representation of a given value, so
>it would be impossible to enforce maximum and minimum values on such
>localized types.  This struck some WG members as taking most of the
>utility out of the proposal, but some WG members insisted that it
>could be useful for an application to know what value space a given
>lexical form represented, even without knowing which value it denoted.
>Eventually, a fuller proposal was developed, but integrating it into
>the design proved to raise a number of difficult design questions.
>The WG was unwilling to answer these questions before they had
>received adequate consideration and the implications were fully clear,
>and so in the end the proposal for abstract simple types, which was
>intended in part to allow schema authors to define types for
>non-gregorian dates (and in the long run to provide a foundation for
>standardizing such types) was rejected.  It will not be part of XML
>Schema 1.0.
>The WG regrets that we were unable to find a way to incorporate a
>reliable method for integrating non-Gregorian dates into XML Schema
>1.0; we hope that we will be able to turn to this question in a later
>version of XML Schema.
>It would be helpful to us to know whether you are satisfied with the
>decision taken by the WG on this issue, or wish your dissent from the
>WG's decision to be recorded for consideration by the Director of
>the W3C.
>with best regards,
>-C. M. Sperberg-McQueen
>  World Wide Web Consortium
>  Co-chair, W3C XML Schema WG
Received on Thursday, 5 October 2000 21:49:49 UTC

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