Re: What are the characteristics of a good type system for XML
Jeni Tennison scripsit: > John brought up the issue of types that don't have total ordering. The > lack of total ordering of durations and date/times with or without > timezones has been a real pain in XPath 2.0 because for optimisation > purposes you really need just one of $a = $b or $a != $b to be true. > You could, of course, introduce three-valued logic to cope with the > ambiguity, but I'd be interested if anyone had any other bright ideas. IMHO the whole notion of times without zones is so much $*@(. The value type should be just UTC instants or periods, and it should be possible to specialize the type Date to the type ESTDate, or America_New_York_Date, supplying the default timezone as part of the type. The problem of incommensurable durations (which is longer, 60 sec or 1 min?) is much more serious, and I don't see that anything can reliably be done about it. Durations are simply not totally-ordered. -- "Do I contradict myself? John Cowan Very well then, I contradict myself. jcowan@r... I am large, I contain multitudes. http://www.ccil.org/~cowan --Walt Whitman, _Leaves of Grass_ http://www.reutershealth.com
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