Subject: RE: [xsl] Timezone concept broken in XPath 2.0? From: "Michael Kay" <mike@xxxxxxxxxxxx> Date: Mon, 10 Nov 2008 11:01:30 -0000 |
> It's easy enough to do it yourself. The reason I posted is > rather that whether or not adjust-dateTime-to-timezone($dt) > and its two fellows in XPath 2.0 return a correct result for > a given point in time $dt depends on whether or not the > offset from UTC at the time of processing matches the offset > from UTC in effect at $dt - and this strikes me as odd. There are a zillion features that aren't supported in the XPath function library. After all, it only contains a little over 100 functions: by way of comparison, the Java class library contains over 3700 classes, and heaven-knows how many methods. So the fact that the function you want is not present is not something one can regard as a bug. The fact that civil timezones aren't supported is largely because they aren't supported in XML Schema, which in turn is because they aren't supported in ISO 8601. Although it's true that many applications have to cope with civil time displacements, it's equally true that many applications have to cope with changing tax rates and exchange rates. Would you expect a generic function library to know about such things? I think there is something in the argument that this kind of thing belongs more in the application layer than the technology layer. There are many practical difficulties. How would we specify the result of such functions (by reference to the Olson database, or by reference to the decisions of national governments?) How far into the past and the future would we expect an implementation to have information about civil time zone displacements? Would we require the information to be available for the whole world, or only those parts of the world that a particular vendor is interested in? Would we need to have conformance rules requiring an implementation to be updated within N days of a legislative change (or a change to the Olson database?) What happens when there is disputed authority, e.g. as in Tibet? Michael Kay http://www.saxonica.com/
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