Re: [saxon] How can an empty array be an instance of an array that contains something?

It's the old paradox of universal quantification applied to an empty set: when there are no unicorns, "every unicorn has one horn" and "every unicorn has three horns" are both true. Bertrand Russell used the example "The present King of France is bald" (https://en.wikipedia.org/wiki/Definite_description).

> [] instance of array(xs:string)

is true if every member of array is of type xs:string, and under the usual conventions of predicate logic, that statement is true when the array has no members.

Michael Kay
Saxonica

> On 28 Aug 2020, at 09:32, Ihe Onwuka <[email protected]> wrote:
> 
> This returns true for xs:string and xs:integer
> 
> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform <http://www.w3.org/1999/XSL/Transform>" 
> xmlns:xs="http://www.w3.org/2001/XMLSchema <http://www.w3.org/2001/XMLSchema>"
>                 xmlns:array="http://www.w3.org/2005/xpath-functions/array <http://www.w3.org/2005/xpath-functions/array>"
>                 xmlns:map="http://www.w3.org/2005/xpath-functions/map <http://www.w3.org/2005/xpath-functions/map>"
>                 version="3.0" expand-text="yes" exclude-result-prefixes="array map xs">
>    <xsl:template name="xsl:initial-template">
>   {[] instance of array(xs:string)}
>    </xsl:template>
> </xsl:stylesheet>
> 
> Getting this on saxon 10.1
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