- From: <Noah_Mendelsohn@lotus.com>
- Date: Thu, 5 Jul 2001 12:03:36 -0400
- To: "Jeff Rafter" <jeffrafter@definedweb.com>
- Cc: vdv@dyomedea.com, xmlschema-dev@w3.org
Jeff Rafter writes: >> does this mean that an optional Time Zone Qualifier >> should be added Not sure, but there is some background that may be of interest. First, many readers fail to recognize that in XML Schema Datatypes, timezone indicators are in the lexical representations only. Their status is similar to leading zeros, or exponential notations (1E+2) vs. unnormalized floats (100.0); timezones are visible, but not considered to affect the value of the time or integer respectively. The times themselves are all effectively converted to a fixed UTC form for comparison or other use as values. This also has the interesting effect that two different times in different timezones can be considered equal for purposes of enumeration, as are the two floats above. I argued against this design for timezones in particular, as I think it violates least-astonishment for users, but there it is. I believe that users consider timezones more significant than leading zeros. No matter, that is the starting point for any future evolution. I would have preferred to allow no timezone at all than one that has such minimal effect on semantics and comparison. Also, Lotus (my employer) has some experience building timezone-aware applications. Turns out we have had bugs reported, in calendaring applications for example, that were caused by political rather than technical actions. A user schedules a meeting at 3PM in GMT-6, but they really think they're scheduling it in Chicago. Chicago changes its laws, and the calander rings the alarm too early or late...it is indeed GMT-6, but it's no longer 3PM in Chicago. These are real bugs from real users. Some people argued for making the timezone dependent on an online catalog...I think many of us feel that has a variety of undesireable characteristics. On the other hand, this should be taken as a warning that solving users' problems with timezones is not nearly as easy as it appears, and sometimes it is better to do less than to add complexity that doesn't solve the problem. For better or worse, schemas effectively provides timezone markers primarily as a convenience to those recording times in an XML document; it carries little or no semantics compared to the same time in UTC. ------------------------------------------------------------------------ Noah Mendelsohn Voice: 1-617-693-4036 Lotus Development Corp. Fax: 1-617-693-8676 One Rogers Street Cambridge, MA 02142 ------------------------------------------------------------------------
Received on Thursday, 5 July 2001 12:09:07 UTC