count all the distinct timezones in an XMLdocumentusing XPath

[Matthew Rawlings]

Thanks to David Carlisle and Mike Kay I found my mistakes and solved the
problem. The final form of the XPath I used is below:

 

count(distinct-values(//((element(*, xs:date)|attribute(*,
xs:date))/timezone-from-date(.),(element(*, xs:dateTime)|attribute(*,

xs:dateTime))/timezone-from-dateTime(.)))) eq 1

 

I am glad I can express it in pure XPath rather than XQuery as then I can
use it in a xs:assert in a schema written in XML Schema 1.1.

 

I agree with Mike's point about polymorphism - why can't timezone-from-date
and timezone-from-dateTime be the one function with either a xs:date or
xs:dateTime parameter. Both functions return a xs:duration and do the same
thing. It would make the XPath much simpler.

 

 

 

 

  _____  

From: http://x-query.com/mailman/listinfo/talk [mailto:http://x-query.com/mailman/listinfo/talk] On Behalf
Of Michael Kay
Sent: 12 December 2008 11:48
To: 'Matthew Rawlings'; http://x-query.com/mailman/listinfo/talk
Subject: RE:  count all the distinct timezones in an
XMLdocumentusing XPath

 

The nearest to a map() function is the "for" expression

 

count(distinct-values(for $x in //element(*, xs:date) return
timezone-from-date($x), 

                               for $x in //element(*, xs:dateTime) return
timezone-from-dateTime($x), 

                               for $x in //element(*, xs:time) return
timezone-from-time($x))) eq 1

 

But there is also the "simple mapping operator" "/" -

 

//element(*,xs:date)/timezone-from-date(.)

 

It's rather tedious that there's no polymorphism (or support of union types)
so that the different date/time types have to be enumerated like this.

 

Note that if a dateTime has no timezone, timezone-from-dateTime() will
return (), which is ignored in counting the distinct values.

 

Michael Kay

http://www.saxonica.com/ 

 


  _____  


From: http://x-query.com/mailman/listinfo/talk [mailto:http://x-query.com/mailman/listinfo/talk] On Behalf
Of Matthew Rawlings
Sent: 12 December 2008 11:27
To: http://x-query.com/mailman/listinfo/talk
Subject:  count all the distinct timezones in an XML
documentusing XPath

How can I count all the distinct timezones in a single XML document using
XPath?

 

I have an XML document with many elements and attributes with the type
xs:date or xs:datetime. One of the rules of the system receiving my document
is that all timezones must be the same in the document. Ideally I would like
to express this constraint purely in XPath 2 rather than XQuery so I can put
the constraint in a xs:assert statement.

 

If there was a map function in XPath I would write something like this:

 

count(distinct-values(map(fn:date-from-timezone(), //(element(*,
xs:date)|attribute(*, xs:date)|element(*, xs:datetime)|attribute(*,
xs:datetime))))) eq 1

 

This XPath would return true if all timezones were the same, and false
otherwise.

 

However there is no map function in XPath, so how can I achieve the same
thing without it? What is the nearest I could get.

 

- Matthew

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