> >  <person><first>Michael</first><last>Kay</last></person>
> 
> 
> Out of interest, what is the reasoning behind allowing a 
> mixed content element's typed-value to be its string value, 
> but making it an error for element-only content?
> 

data-heads vs doc-heads.

The data people felt that saying person='Kay' should be caught as a type
error.

But with mixed content, for example

<title>Water, or H<sub>2</sub>O</title>

it clearly makes sense to say contains(title, 'Water')

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