In XML Schema, a simple type is either a list type, a union type, or an
atomic type; however, these three kinds of simple type are not recognized
explicitly in the type hierarchy. For XPath, it was necessary to distinguish
atomic types from the other kinds of simple type, so xdt:anyAtomicType was
invented to achieve this.

Michael Kay
http://www.saxonica.com/

> -----Original Message-----
> From: Frans Englich [mailto:frans.englich@xxxxxxxxx] 
> Sent: 02 July 2005 21:47
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject: [xsl] What's the difference between 
> xdt:anyAtomicType and xs:anySimpleType?
> 
> 
> Hi,
> 
> I wonder, what is the difference between the xdt:anyAtomicType and 
> xs:anySimpleType? It is a type(duh) and hence can code and 
> definitions depend 
> on it, but other than that, does it have any "effective" impact?
> 
> Why does it exist? If it didn't exist, anySimpleType would 
> have to derive from 
> the imaginary "itemType"; is that the reason? 
> 
> Can the anyAtomicType be considered a "marker interface" for 
> atomic values, 
> but that it in practice is an anySimpleType?
> 
> In the XML.com article titled "The XPath 2.0 Data Model"[1] 
> there's a small 
> hint:
> 
> "The Data Model document adds five new types to the 19 
> primitive types defined 
> in the Part 2 Recommendation: [...] the xdt:anyAtomicType, an 
> abstract type 
> that plugs a newly-discovered architectural hole [...]"
> 
> What was the architectural hole(or where can I read about 
> it), and has it any 
> relation to my question?
> 
> 
> Cheers,
> 
> 		Frans
> 
> 1.
> http://www.xml.com/lpt/a/2005/02/02/xpath2.html