count all the distinct timezones in an XML document using XPath

[Matthew Rawlings]

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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