Very good point. At one time we didn't allow an equality comparison between
durations, largely because of concerns about how it should be defined, given
the XML schema definition of a duration as a 6-tuple (is P1Y equal to
P12M?). In the end we did introduce this notion, partly to ensure that every
document is deep-equal to itself. I think you are right to observe that this
makes the equality operators on the subtypes redundant, and that it also
means equality between duration and one of its subtypes should be
well-defined.
Can I suggest you raise this on the W3C bugzilla?
Michael Kay
http://www.saxonica.com/
-----Original Message-----
From: Frans Englich [mailto:frans(_dot_)englich(_at_)telia(_dot_)com]
Sent: 01 February 2006 01:05
To: xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com
Subject: [xsl] xdt:yearMonthDuration eq xs:duration
Saxon 8.6 fails this expression with XPTY0004, "Cannot compare
xdt:yearMonthDuration to xs:duration":
xdt:yearMonthDuration("P200Y2M") eq xs:duration("P200Y2M")
The XPath 2.0 book specifies these operators:
A eq B xdt:yearMonthDuration xdt:yearMonthDuration
A eq B xdt:dayTimeDuration xdt:dayTimeDuration
A eq B xs:duration xs:duration
It also says this:
<quote>
Any operator listed in the operator mapping tables may be
validly applied to
an operand of type AT if the table calls for an operand of
type ET and
type-matches(ET, AT) is true (see 2.5.4 SequenceType
Matching). For example,
a table entry indicates that the gt operator may be applied
to two xs:date
operands, returning xs:boolean. Therefore, the gt operator
may also be
applied to two (possibly different) subtypes of xs:date, also
returning
xs:boolean.
</quote>
Doesn't type-matches(xs:duration, xdt:yearMonthDuration) hold
true? My point
being that the expression should succeed because
xdt:yearMonthDuration is a
subtype of xs:duration and that the xs:duration-eq operator
therefore can be
applied. If that is the case, which I doubt, the eq/ne
operators for the two
XDT durations are redudant, since the xs:duration-eq/ne
operators covers
them.
What clause in any of the specifications disallow the above operand
combination? (and the others variations by the same principle)
Thanks in advance,
Frans
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