Re: [Michael Kay] RE: <enumeration> of duration types

Dave Peterson <davep@iit.edu> writes:

> It is true that in 1.0, P1Y and P12M are distinct duration values and
> equality is identity.  The general concensus was that this situation
> was unacceptable; it implies that P1Y and P12M are incomparable (not
> less-than, not greater-than, and not identical/equal).  This situation
> has been changed in 1.1.
>
> In 1.1:
>
> Durations have only a month property and a second property.  P1Y and
> P12M are identical; both are (12,0).  OTOH,
>
> Equality in 1.1 is not always identity, and in particular for duration
> both equality and order are determined by adding the durations to four
> standard dateTime values and checking the four resulting pairs of
> dateTime values.
>
> The rule is:  If all four resulting dateTime value pairs are equal,
> then the durations are equal.  If all four resulting dateTime values
> are ordered the same way, then the durations are ordered that way.
> If some of the resulting dateTime values are equal and others not,
> or if the order is not always the same direction, then the durations
> are incomparable.  Clearly then the order is properly tied to equality.
> This is the same algorithm used for order (but not equality) in 1.0.
>
> It's an interesting question whether equality so defined is in fact
> identity.  I believe it is, but I've never sat down and proved it.

So what about P365D?

ht
-- 
 Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
                     Half-time member of W3C Team
    2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
            Fax: (44) 131 650-4587, e-mail: ht@inf.ed.ac.uk
                   URL: http://www.ltg.ed.ac.uk/~ht/
[mail really from me _always_ has this .sig -- mail without it is forged spam]

Received on Monday, 18 April 2005 14:39:43 UTC